Foam concrete is a roof insulation with only two drawbacks

Roof insulation with foam concrete is considered one of the effective ways to retain heat in a house. This building material is suitable for use in private and multi-storey buildings. Foam concrete is distinguished by its strength and durability. Unlike mineral wool or expanded polystyrene, the material is not damaged or deformed under heavy loads. Proper laying of the foam concrete mixture will prevent premature damage to the roof waterproofing.

Foam concrete is a roof insulation with only two drawbacks

Roof insulation with foam concrete is considered one of the effective ways to retain heat in a house. This building material is suitable for use in private and multi-storey buildings. Foam concrete is distinguished by its strength and durability. Unlike mineral wool or expanded polystyrene, the material is not damaged or deformed under heavy loads. Proper laying of the foam concrete mixture will prevent premature damage to the roof waterproofing.

1. Composition and properties of building materials
2. How is it used for roofing?
3. Benefits of use

Composition and properties of building materials

The strength of foam concrete blocks allows it to be used for the construction of low-rise buildings. In this case, the room does not require additional insulation.

The insulation of a pitched roof using foam concrete is due to its reliability and ease of installation. The mixture is made from a solution of cement, sand and water. Foaming is carried out using special equipment. The foam generator evenly distributes air bubbles throughout the solution. Thanks to this composition, foam concrete has the following properties:

• durability;
• compression resistance;
• thermal insulation;
• strength;
• waterproof;
• fire resistance;
• soundproofing.

Requirements for filling material

Foam concrete acts as the base of the roof; it must be protected by the roof. The roofing pie is designed in such a way as to withstand atmospheric loads for a long time, thereby protecting not only the foam concrete, but also all the structures of the house from destruction.

Requirements for foam concrete for the roof:

1. 
   Density: 150-1200 kg/m3. The first indicator provides high thermal protection characteristics of the roof, and the second for structures that require high strength characteristics.

2. In terms of environmental friendliness, no lower than 5 cl., for comparison, wood - 1 cl., brick - 10 cl., foam concrete - 2 cl.
3. Compressibility strength class - B: from 0.75 -12.5, respectively for thermal protection and structural strength.
4. Thermal conductivity coefficient: 0.05 - 0.15 W/m°C. The first indicator is for cold climatic regions, when it is necessary to ensure high thermal protection characteristics of the roof, the second for structures with high strength characteristics, for example, when constructing operational roofs.
5. Water absorption, 10-16% of mass.
6. Frost resistance, F35.

Requirements for a roofing pie:

1. Easy to install, maintain, repair and dismantle.
2. High resistance to mechanical and climatic influences.
3. Excellent waterproofing qualities.
4. Durability from 15 years to 60 years.
5. Heat resistance – no deformation at temperatures above 120 °C.
6. Lightweight reinforcing base.
7. The density of the outer layer is not lower than 80 g/mm2.
8. Light weight, at least 8 kg/m2; with a lower value, the layer thickness may not be sufficient to provide all protective functions.
9. Resistance to UV rays.
10. Wide operating temperature range from -50 to 110°C.
11. Fire and environmental safety, the spontaneous combustion temperature of bitumen is over 300 C, the material is not dangerous in everyday life and does not rot.
12. Moisture resistance – 100% reliability over the entire roof area.
13. Acoustic comfort - do not create noise during rain, hail and hurricanes.
14. Wind resistance must correspond to the climatic characteristics of the area where the facility is located.

Rules for its preparation

Foam concrete is made from cement, sand and water, with the addition of a special foam concentrate and hardener. The kneading is carried out in a foam generator or bar mixer. During the mixing process, air bubbles are uniformly formed in the thickness of the solution, increasing the volume of the product, providing it with a light and less dense structure.

All components are dosed exclusively in accordance with GOST, since the quality of the finished foam concrete directly depends on this. Foaming agents are the most important components in the working mixture.

They can be:

• protein;
• synthetic.

The first ones are higher quality and more expensive:

1. Biopore;
2. Esapon;
3. FoamCem.

The second ones are of lower quality and cheaper:

• FROM TO;
• Arecom-4;
• PB-200.

Work must be carried out at air temperatures above + 10 C.

Pouring the foam concrete base is carried out by using high-quality factory-made foam concrete with a quality certificate, or it is prepared on the work site in mobile concrete mixing plants.

They are capable of supplying ready-made foam concrete into the installed formwork to a height of up to 30 m. For this, you can use both compact pressure units and classic systems with a foam generator operating in automatic mode. They are able to strictly dose all the ingredients according to the recipe in order to achieve the required strength and density.

When performing work on pouring a foam concrete roof, it is prohibited :

• use a mixture obtained by handicraft in low-power concrete mixers;
• pour foam concrete without a quality certificate or having a heterogeneous structure.

It is also unacceptable to fill a monolithic structure in small batches and with breaks.

Additional information about preparing the solution:

How is it used for roofing?

Since mineral wool and expanded polystyrene do not have sufficient strength, when using such insulation materials, the roofing waterproofing coating is destroyed within 2 years. This is due to the formation of “lenses”, which, due to the violation of the integrity of the upper ball, allow moisture to pass into the roof. This occurs under the pressure of the weight of snow or people walking on the roof. It is possible to prevent the formation of “lenses” by using foam concrete as an insulating material. This building material is resistant to compression and does not deform under load. The concrete dough is laid directly on the vapor barrier layer, having previously divided the plane into segments. Using a hose, foam concrete is supplied directly to the roof. After the screed has dried, the roof is covered with waterproofing materials and roofing.

Roof insulation by spraying and pouring

The most technologically advanced methods of insulation , according to b2bb2c.ru, are those that allow you to lay thermal insulation on an area of ​​arbitrary geometry, a large surface with the involvement of a minimum number of people, and quickly, efficiently, reliably, conveniently... Does anyone think otherwise? In general, it was a rhetorical question.

So, the criteria described above include insulation materials that are obtained directly on the roof, on the insulated surface, by pouring or spraying ingredients. Those known to the SD Department include polyurethane foam, foam concrete and polystyrene concrete. I should immediately note that there are other materials that can be poured and sprayed, for example, ecowool, but, in my opinion, it is wrong to use them for roof insulation. Therefore, they are not mentioned below.

Let's start with the “king” of thermal insulation, with material No. 1 for roof insulation . This is polyurethane foam.

Polyurethane foam for insulating flat roofs

Polyurethane foam is convenient due to its manufacturability. Polyurethane foam is sprayed with special equipment, the liquid falling on the surface foams, increases in volume, and a layer of insulation is formed. The photo below shows the moment of repairing a flat roof. I would like to note right away that here they took the path of simplifying and speeding up the technology, namely: no one removed the old roof covering (and even more so what was under the roll). We limited ourselves to cutting out and draining the obvious bubbles.

Polyurethane foam cannot be left “naked” in the sun. Ultraviolet radiation will make it fragile within a couple of months. Therefore, after the material is painted, it is protected.

In general, polyurethane foam is slightly hygroscopic. Therefore, it can serve as additional waterproofing. But still, it should be remembered that this is, first of all, a material for insulating a flat roof, and its waterproofing properties are secondary. Therefore, leaving it as a roofing finish, even if it is painted against ultraviolet radiation, is, in my opinion, not enough. Depending on the influence of the external environment, operating conditions, etc., such a roof will last for five years. Then - again repairs. But the good news is that repairs will have to be done in separate local areas. And the polyurethane foam is very repairable: I cut out, cut down the collapsing section and dusted it over again.

In general, the roof in the photo, after insulation with polyurethane foam, will be sprayed with painting and waterproofing material. And, to be honest, it won’t be liquid rubber. In general, applying liquid rubber over polyurethane foam is a separate topic for discussion. I will only note that if you cover polyurethane foam with liquid rubber (subject to a number of requirements), then the polyurethane foam must be produced in a high-pressure installation. If the insulation of a flat roof is carried out with polyurethane foam sprayed with a low-pressure unit, then a screed should be made on top of the polyurethane foam and only then liquid rubber should be sprayed.

Some people complain that polyurethane foam is flammable, but this is not entirely true. The higher the density of polyurethane foam, and for roofing a density of 60-80 kg/m3 is required, the worse it burns. More precisely, it does not burn at all, but melts, and then only when exposed to fire. If you remove the flame source, the PPU goes out. However, if you install a screed on top of polyurethane foam, then the “fire” issue disappears completely.

By the way, an experienced operator can use polyurethane foam to make or “correct” the deviation. All that remains is to install a screed on top, but significantly less cement mortar will be needed, because It is the polyurethane foam that will form the roof slopes. The advantage is that the thickness of the insulation will be “heavy”, but the deflection will be many times easier than if it is done entirely with concrete. Minus - the price of the issue will increase, because... A cube of polyurethane foam with a density of 60 is several times more expensive than a cube of cement-sand mortar.

It is the price of polyurethane foam, as a rule, that is what really slows down the mass use of polyurethane foam as insulation on flat roofs.

Now let's look at another technologically advanced material for roof insulation , the cost of which is lower than that of polyurethane foam. This is foam concrete.

Foam concrete for insulating flat roofs

Most people know that blocks for walls and partitions are made from this material, but foam concrete can also be poured directly on site. The thermal conductivity coefficient of foam concrete is higher than that of polyurethane foam, so its thickness is greater than polyurethane foam, and accordingly the mass of foam concrete insulation will be heavier. But foam concrete is still significantly lighter and warmer than conventional mortar.

Therefore, it is quite reasonable, for example, to install special formwork and pour a layer of light foam concrete (density 250 kg/m3) on top of the vapor barrier (density 250 kg/m3), thus insulating and pitching the roof. Then place a strong screed on top of the lightweight foam concrete.

The advantage of foam concrete for insulating a flat roof is that it is cheap and technologically advanced.

The downside is that according to modern energy saving requirements, a layer of insulation - foam concrete - may require up to 1 meter. And this, whatever one may say, is a load on the roof. There was a time, at the beginning of the two thousandth, when lightweight poured foam concrete was very widely used for insulation and slope of roofs. St. Petersburg was especially different in this regard. But then, as a rule, the foam concrete layer was made from 270 to 350 mm.

As of the summer of 2012, the use of foam concrete, both for thermal insulation of flat roofs and for solving other insulation problems, has decreased in Russia as a whole. This is the subjective opinion of the author of B2bB2c.ru.

If a foam concrete specialist ever reads this article and refutes the above, a review of the real state of affairs with foam concrete as a material for insulation can be posted on the B2bB2c.ru website.

The next interesting method of insulation is pouring polystyrene concrete for thermal insulation of a flat roof.

Polystyrene concrete for insulating soft roofs

This is a kind of hybrid of foam concrete and expanded polystyrene. The photo below shows the process of pouring polystyrene concrete.

Polystyrene concrete is good for insulating a flat roof, but it is obvious that the use of this material, like foam concrete, for local repairs is almost impossible. More precisely, it is possible, but it is so difficult that no one is doing it - it is much easier to use slab materials for insulation.

Benefits of use

Foam concrete is used as insulation for roofing. Since up to 30% of heat is lost through the roof, the choice of material must be approached responsibly. Roof insulation with foam concrete has the following advantages:

The material can easily withstand the load of snow and people walking.

• Resistance to mechanical loads. Even the significant weight of snow that accumulates on the roof in winter and the walking of people is not capable of damaging the insulation ball.
• Waterproof. The ingress of moisture does not lead to deformation of the building material and does not provoke a loss of thermal insulation abilities.
• Fire resistance. Unlike expanded polystyrene and mineral wool, foam concrete does not burn, so a spark hitting the roof or exposure to open fire cannot ignite the surface.
• Unattractive to rodents. A common cause of damage to the integrity of thermal insulation materials is the impact of mice, but the foam concrete coating is not affected by them.
• Long service life. A foam concrete roof can last as long as the entire house.
• Light weight. The cellular structure of the building material makes it light, which allows the insulation to be used on structures with low strength.

The disadvantages of the material include poor air circulation and the toxicity of the foaming agent, so it is not recommended to insulate the roof with a foam concrete mixture from the inside.

A sufficient number of advantages of foam concrete make it a popular building material for insulating pitched roofs. In country houses, such technology provides additional space for arranging a sports ground or recreation area. The durability of the material will eliminate the need to carry out repair work on the roof every 2 years.

Possible difficulties

It cannot be said that it is impossible to make a foam concrete roof yourself, although this will be very difficult to do. Modern technologies of this design require high-quality material and expensive equipment to create a base.

In addition, for residential and industrial buildings such work must be carried out exclusively by companies that have the appropriate permits, otherwise the facility will not be accepted for operation.

The main difficulties and errors in creating a foam concrete roof begin during the manufacturing process of foam concrete if the proportionality of its composition is violated.

In addition, errors in creating such a roof include:

• 
  Violation of the roof slope, poor water drainage;

• the drainage system is incorrectly executed, water stagnation on the roof and the destruction of the “roofing pie”;
• violation of the design composition of foam concrete;
• the reinforcement frame is incorrectly calculated and installed;
• the distance for supporting the foam concrete base on the load-bearing walls is not maintained;
• a monolithic belt is not installed on walls made of light blocks;
• violation of the production of formwork in terms of the choice of materials and the arrangement of supports;
• the volume of required foam concrete was incorrectly calculated; the foundation was poured in parts from different batches of foam concrete;
• the poured surface has not been vibrated;
• violation in the maintenance stage of the filled surface, there is no protection of it from moisture and UV rays;
• the “roofing pie” is incorrectly selected, there is no protection against steam and moisture.

Smart choice

Roofs that are insulated using conventional materials, for example, mineral wool or expanded clay concrete, can begin to “deteriorate” after just a couple of years. The reason for this is the action of the merciless summer sun. Under its influence, moisture (water, condensation that soaked the material during the cold season) begins to evaporate from the thermal insulation. Due to the “vapors” under the waterproofing, excess pressure is created, causing the roof to peel off from the base.

Nowadays foam concrete is often used as insulation on roofs. For our latitudes, this material is relatively new. Meanwhile, back in the fifties of the last century, Germans and Italians equipped their homes with similar roofing, and after that the material became widespread in other European countries.

Foam concrete is a concrete mixture with the addition of foam produced by a foam generator or pressure unit. The cellular structure is obtained due to the precise distribution of air bubbles throughout the mass.

Main characteristics

Foam concrete is suitable for roofing according to a number of parameters:

• Stability of material geometry (rigidity). For example, due to the uneven mechanical load on the roof and the thickness of the screeds, recesses called “lenses” are formed on conventional roofs (moisture accumulates in them, which penetrates into the roof itself, and over time, swellings appear on the surface). With the use of foam concrete, such troubles do not occur.
• Consistency of technical parameters (uniformity). A traditional roof compresses under loads (cover of snow, people on the roof). More precisely, this happens with insulation, the thermal insulation qualities of which decrease. The ability to store heat is also reduced when moisture enters the roof body. Foam concrete does not have such disadvantages.
• Long service life. Cellular concrete is a material that does not “age”, unlike traditional insulation materials. It does not rot and is not affected by mold or mildew. In terms of strength, according to manufacturers, the material is second only to stone, but in terms of weight it is still foam. However, it is worth remembering that longevity directly depends on compliance with production technology, pouring conditions, and hardening.
• Fire safety. Many traditional insulation materials burn and smolder when exposed to direct flame or sparks. Foam concrete is not flammable, has a fire resistance degree of I, which is proven by relevant tests.

Foam concrete has the advantage of being environmentally friendly. In terms of this indicator, it loses only to wood (for the latter, the environmental friendliness coefficient is equal to one, cellular concrete is assigned a two). In addition, the material has good noise absorption properties and prevents heat loss (approximately 20-30% of the heat from the house can escape through the roof).

Advantages and disadvantages

In practice, foam concrete roofs have demonstrated their distinctive characteristics compared to roofs made of conventional concrete and aerated concrete. In general, they are inferior to ordinary concrete in almost all main indicators: strength, durability and frost resistance. It has advantages over concrete only in weight, cost and heat-shielding characteristics.

Advantages of a foam concrete roof compared to aerated concrete:

1. Moisture absorption is an advantage of foam concrete due to which it needs a lower level of water protection.
2. The environmental safety of foam concrete is slightly higher, since aerated concrete is produced by a reaction between lime and aluminum, releasing hydrogen, which continues to be partially released during the operation of the product.
3. Thermal protection is higher for foam concrete.
4. Fire resistance according to this indicator, both materials are equal and are non-flammable.
5. The cost of foam concrete is much cheaper than aerated concrete.

Disadvantage of a foam concrete roof compared to aerated concrete:

1. Despite the fact that the density of both materials ranges from 400 to 1200 kg/m3, at the same density foam concrete is less durable and reliable.
2. Foam concrete exhibits shrinkage of 1 to 3 mm/m, while aerated concrete shrinks below 0.5 mm/m.
3. In terms of frost resistance, aerated concrete is 2, and sometimes even 3 times more reliable than foam concrete.

Application area

This insulation can be used on almost any roof - old, new, damaged, on the roof of an industrial enterprise or residential building of various storeys. Due to the light weight of the material, it can be poured onto a light floor (wood, corrugated board). It is thanks to the relative “weightlessness” that experts recommend the use of foam concrete as thermal insulation during roof reconstruction, for old floors (depending on how much load they can withstand) . Foam concrete is also indispensable for arranging or rebuilding complex structures with abutments and several slopes. Another advantage of cellular concrete is that the surface for pouring it does not need to be specially leveled. The material itself will fill all the roughness.

Using foam concrete reduces labor costs for roofing. It is supplied to the roof with hoses (maximum height - up to thirty meters) from a special installation located on the ground (capacity - up to 15 cubic meters per hour). In this case, there is no need to gradually lift and distribute thermal insulation in batches, as happens when using other materials. If it is necessary to carry out work at an elevation above the stated thirty meters, compact equipment can be located closer to the place of work - only the raw materials themselves will need to be delivered there.

Note. The thickness of the layer is determined by thermal technological calculation (on the Internet you can find elementary formulas, tables with thermal conductivity coefficients of certain materials, online calculators).

After the pouring is completed, the foam concrete is allowed to harden. After 24 hours you can walk on it on a flat roof. After a week to ten days (this depends on the outside temperature), it is treated with a primer, waterproofing is glued or fused, and a roofing carpet can be laid on top (it can be anything, the choice, in particular, depends on the operational requirements, the desires of the building owners, etc. similar).

Average costs for materials and labor

The cost of a foam concrete flat roof depends on the cost of the raw materials. The main costs are the cost of foam concrete, transportation costs, lifting to a height and installation work on arranging the base of the roof.

The average cost of monolithic foam concrete for roofing , depending on the density per 1 m3/m2 with a layer thickness of 150 mm :

• 250 kg/m3 — 3,341/502 rub.
• 300 kg/m3 — 3,671/550 rub.
• 400 kg/m3 — 4,357/653 rub.
• 500 kg/m3 — 4,579/686 rub.
• 600 kg/m3 — 4,791/718 rub.
• 700 kg/m3 — 4,995/749 rub.
• 800 kg/m3 — 5,141/771 rub.
• 900 kg/m3 — 5,476/821 rub.
• 1000 kg/m3 — 5,657/848 rub.

For large volumes, most artists offer a discount. Further, the cost will be increased by the costs associated with installing a soft roof; if the customer chooses a standard “roofing cake”, then the list of works on installing a soft roof will consist of :

• preparation of the base - removal of snow, ice and drying;
• adhesive vapor barrier;
• insulation with 120 mm slab;
• sloped wedge-shaped insulation;
• making a separating geotextile layer at the junction;
• installation of a 1.5 mm PVC membrane;
• installation of drainage funnels and pressure strips.

The average cost of such work is 1,400 rubles/m2.

In order to calculate in more detail the cost of a soft roof for a foam concrete roof based on specific installation conditions, you can use more detailed prices per 1 m2 with and without materials :

1. 
   Vapor barrier device made of fused materials - 220/100 rubles.

2. Insulation of mineral wool 100 mm in 2 layers with mechanical fixation - 465/165 rub.
3. Thermal insulation XPS 100 mm in 2 layers with mechanical fixation - 630/130 rub.
4. Angle with wedge-shaped insulation - 6050/2100 rub./m3.
5. Screed device 580/450 rub.
6. Installation of 2 layers of deposited material - 740/440 rubles.
7. Installation of 3 layers of rolled material - 1040/620 rubles.
8. Arrangement of connections up to 0.6 m - 550/325 rub./m.p.
9. Installation of a carpet made of PVC membrane with a ballast/inversion system - 600/150 rubles.
10. Installation of a PVC membrane carpet with mechanical fastening - 670/220 rubles.
11. Waterproofing with TPO membrane - 720/240 rub.

To calculate the cost of a 10x10 m roof made of foam concrete with a density of 600 kg/m3 with a layer of 150 mm, you will need to perform the following work :

1. Laying a foam concrete base per 1 m2, total - 4,791 rubles, including work - 718 rubles.
2. Vapor barrier device - 220/100 rub.
3. Insulation with 100 mm mineral wool in 2 layers with mechanical fixation - 465/165 rub.
4. Screed device - 580/450 rub.
5. Installation of 2 layers of deposited material - 740/440 rubles.
6. Installation of a PVC membrane carpet with mechanical fastening - 670/220 rubles.
7. Waterproofing with TPO membrane - 720/240 rub.
8. Total: 8186 rub. for 1 m2.
9. Total: 10x10x8186=818600 rub.

Scope of application of foam concrete

Foam concrete is a high-quality material, which, due to its improved performance characteristics, is now successfully used in the form of blocks in the construction of residential buildings, shopping and office centers, and production workshops. In fact, this material is nothing more than a highly porous mass consisting of cement, sand and a special substance - a foaming agent. When hardened, this mixture is transformed into a kind of artificial stone, which we call foam concrete. For this reason, with the development of methods that make it possible to produce foam concrete mass that is stable in terms of parameters directly on construction sites, the scope of use of such material has increased significantly.

There is nothing strange in the fact that now monolithic foam concrete is beginning to gain such popularity. The success of the material lies in its unique characteristics. The principle of its manufacture makes it possible, without much effort, to obtain directly at the site under construction (taking into account the requirements) an insulating and at the same time structural material with clearly defined parameters. Foam concrete goes well with all kinds of materials and structures, significantly facilitating various works and reducing the time required to complete them.

Advantages of using foam concrete for roofing

Everyone knows that the main disadvantage of flat roofs, in particular those in use, is their low reliability. Conventional roof slabs quickly become damaged within two years from the date of their installation. And this is not necessarily due to low-quality roofing materials. The roofing pie is subjected to numerous impacts, which together lead to the complete destruction of building structures. The service life of a roofing pie is influenced by how consistently all its layers, including thermal insulation, interact.

Most often, backfill material or mineral wool slabs are used for roof insulation. Due to its unique properties, mineral wool can provide high thermal insulation, but when moisture is absorbed into it, it loses these abilities.

Damage to roofing systems occurs most quickly in the summer due to the fact that the moisture accumulated in the insulation during evaporation creates pressure, as a result of which the roofing peels off. Moisture can penetrate into the thermal insulation due to violations of installation technology when laying mineral wool is carried out in damp weather. In addition, if the vapor barrier layer is damaged, moisture begins to be absorbed into the mineral wool material, as if into a sponge. Also, mechanical stress can lead to the accumulation of moisture on the roof (for example, the roofing material is pressed under the weight of snow).

All these disadvantages of conventional roofs can be forgotten if you use foam concrete to insulate the roof. The scope of use of foam concrete in roofing structures is absolutely unlimited. The material does not absorb moisture and is not afraid of high snow loads; when laid, it forms a completely waterproof monolithic layer. The service life of such insulation is incomparably higher than that of conventional thermal insulation materials. It has been practically proven that a roof with such insulation does not require full-scale repairs throughout the entire period of operation. In addition, by increasing the rigidity of the roof structure, its shape and size remain unchanged.

• Electric heated floor

• Installation of ventilation systems

• Pipes for internal sewerage

Another important advantage of monolithic foam concrete is that it does not burn at all. No sparks or open fire can ignite a roof insulated with foam concrete. On top of that, foam concrete has a small mass, so it is suitable for installing roofs on buildings whose load-bearing structures have low strength. It is allowed to use foam concrete even on light floors made of profiled sheets.

Pouring is carried out using professional equipment for the production of foam concrete. The mini-factories that our company produces offer you the opportunity to start producing foam concrete of a wide range of densities, from 150 to 1200 from thermal insulation to structural load-bearing, respectively. The laying principle makes it possible to supply the liquid mixture to a height of up to 30 m. What is especially good is that foam concrete reliably adheres to surfaces made of any materials, and the technology for pouring it does not require leveling the bases and sealing cracks.

Recommended Products

Mini-plant SSM-1000-40M, equipment for.

The updated design of the mini-plant SSM-1000-40M has a built-in foam generator and a pump for supplying foam concentrate, and the bearing assembly of the mixer is equipped with a pressure compensation chamber to increase the service life of the entire assembly and eliminate the loss of cement laitance.

Step-by-step instructions for creating

The construction of a monolithic foam concrete base for a roof assumes that the solution must be poured into a horizontal formwork, which in practice is also called a “deck”. The formwork can be installed from a ready-made prefabricated panel structure or from wooden formwork, plywood panels, while the inner surface is covered with a waterproofing film.

Step-by-step instructions for creating a foam concrete roof for a house:

1. Vertical support posts are installed in increments of 1 m and a distance from the walls of 0.2 m. It is better if telescopic posts with height adjustment are used as supports. They are able to withstand the weight of a foam concrete base up to 2 tons; the cost of renting such formwork is 160 rubles. per 1 m2 of area.
2. Crossbars in the form of longitudinal beams, I-beams or channels capable of holding the formwork are placed on top of the racks.
3. The formwork is laid horizontally on the crossbars. If non-factory formwork is used, but home-made, then additional transverse beams are laid on top of the longitudinal beams.
4. Perfectly fitted moisture-resistant plywood without cracks is laid on top.
5. The formwork is installed in such a way that the slab overlaps the wall at a distance of at least 150 mm, where a vertical fencing of the formwork contour is made.
6. Use a level to check the slope level from 1 to 4 degrees.
7. If the base for pouring is made of metal, its surface is lubricated with machine oil, and the wooden base is covered with film so that after completion of the work the formwork can be easily removed.
8. A reinforcement frame is installed from 2 meshes of steel reinforcement A-500C with a diameter of up to 12 mm, with cells of 200x400 mm, the mesh is knitted with 1.5 mm knitting wire, the rods are connected with an overlap of at least 0.40 m.
9. A necessary element for connecting foam concrete walls and a foam concrete base is a stiffening belt made of a continuous reinforced concrete structure located along the perimeter of the load-bearing walls at the floor level.
10. The reinforced mesh must extend onto the load-bearing walls by 150 mm, and the ends of the reinforced mesh must have a gap with the walls of the vertical formwork along the entire perimeter of at least 25 mm.
11. The bottom layer of the mesh should also have a gap of 25 mm with the formwork from the top and bottom edges of the future base. To do this, plastic clamps are installed under the lower reinforced mesh with a step of 1 m at the intersection of the reinforced rods.
12. The thickness of the base should correspond to a ratio of 1:30, where 1 is the thickness of the base, and 30 is the length of the span. For example, when the span is 6 m, the thickness of the base must be at least 200 mm. In this case, the distance between the reinforcing mesh is from 120 to 125 mm.
13. To ensure compliance with the intergrid distance using a bending tool, special clamps are made from 10 mm rod and with upper and lower shelves of 350 mm each and a vertical dimension of 120 mm. Installation of such clamps is carried out in rows every 1 m with a staggered arrangement.
14. To strengthen the support of the foam concrete base on the roof, install end clamps every 400 mm along the ends of the reinforcement frame.
15. In order for the upper and lower mesh to take the load as a single structure, connectors are installed every 400 mm, and 700 mm from the support area after 200 mm.
16. It is better to pour foam concrete from a mixer, this will ensure the uniformity and strength of the resulting roof base.
17. It is necessary to pour simultaneously without interruptions, in a layer with a working thickness, but not less than 150 mm.
18. Before pouring begins, frames and boxes for technological openings: ventilation ducts and chimneys must be installed in the base.
19. After pouring the foam concrete, the mass is compacted by vibration using deep or surface vibrators operating under compressed air or from the mains.
20. Densely reinforced bases are compacted only with external vibrators for 30 - 60 seconds, the exact time will depend on the plasticity and mobility of the foam concrete.
21. Excessive vibration of the concrete mixture should not be allowed, as this can cause emergency delamination of the foam concrete.
22. The step of rearrangement of internal vibrators is taken from 1 - 1.5 of their working radius.
23. When performing compaction, it is forbidden to lower the vibrator onto embedded parts or reinforcement structures; in these places, the mixture is compacted manually - by bayoneting.
24. Vibration is carried out until the foam concrete mixture stops settling, laitance appears on the surface and the release of air bubbles stops.
25. After pouring, the foam concrete is cared for to ensure the operating temperature of hardening and protect it from rapid drying. To do this, it is covered from exposure to sunlight with a tarpaulin or bags and rain film.
26. Periodically for 14 days, concrete is watered at a rate of 0.5 -1 l/m2.
27. After the base has completely hardened, the formwork is removed and the construction of the soft roof begins.

Soft covering device on a flat base

Most often, bitumen and resin materials are used for soft roofing, the former include roofing felt, the latter - derivatives of roofing felt. During installation, the following method is used:

• gluing rolls on hot bitumen mastics;
• on cold rubber-bitumen and bitumen-polymer adhesives.

For heating, the fire method can be used using gas burners and without fire using infrared radiation. Some types of roofing materials come with an adhesive backing.

Classic roofing pie for a foam concrete roof:

1. Foam concrete base.
2. A vapor barrier layer in the form of a vapor barrier membrane to protect against wet vapors from the room that are formed during human activity.
3. Penoplex insulation or mineral wool.
4. Waterproofing layer.
5. Outer protective layer.

Rolls are rolled out a day before the start of work so that the rolls can be leveled as much as possible and cut along the length of the roof with an addition of 250 mm for bends through the parapet.

Technology for installing a soft roof on a foam concrete base:

1. Prepare the roof base - remove all dirt.
2. The base is primed using an epoxy primer, at the rate of 0.2 kg/m2 for a porous surface, and 0.12 kg/m2 for a non-porous surface. The primer is pre-mixed with a low-speed mixer until smooth, and then diluted with water in the required ratio.
3. The primer is applied to the surface with a paint roller.
4. Special reinforcement is carried out according to the scheme: a layer of special mastic at a ratio of 14 kg/m3, later a construction bandage is mounted into it and covered with another layer of mastic.
5. Install a vapor barrier layer.
6. Install a layer of insulation.
7. Install a waterproofing layer and, if necessary, an external covering.

Due to the small slope of the roof, it is important to prevent the accumulation of water on it and ensure its high-quality drainage into the environment, therefore a drainage system must be installed on such roof structures. Its characteristics are determined during the design of the house, according to the design solution of the flat roof and the climatic characteristics of the area.

Roof insulation with foam concrete

Cottages with a flat roof in a style close to constructivism are elegant, laconic and economical. The installation of a flat roof is much simpler than a pitched roof. But such a solution in a private house does not imply the presence of an attic, which serves as an air gap and therefore requires effective thermal insulation. The optimal solution for a house with a flat roof is to insulate the roof with foam concrete, both for new construction and for renovation.

Properties of foam concrete and methods of roof insulation

Foam concrete belongs to cellular concrete. It is formed during the hardening process of a solution of cement, sand, water and foaming agent. The cellular structure of the material is created by air bubbles evenly distributed throughout the mass of the material. Foam concrete is durable, water-, fire- and wear-resistant, and has good heat and sound insulation properties. The material is durable - even after 50 years it does not lose its performance qualities, and its strength exceeds its original one.

To insulate the roof, monolithic technology is most often used - a layer of foam concrete is poured directly on the roof. Sometimes, in the absence of special equipment, block foam concrete is used with filling the cracks with expanded clay. The monolithic method requires less material, provides minimal thermal conductivity, and does not allow the appearance of “cold bridges”. It is especially effective for complex roof structures with adjacent pitched and flat areas: the insulation fills all the cracks and cracks and does not create significant shrinkage when drying.

Call and receive

• 
  How to choose a window sill?

• Installation of PVC windows

• Covering the drain hole with your own hands

free consultation and cost estimate

roof insulation with foam concrete on a turnkey basis

Equipment and accessories for installation

Equipment for pouring a monolithic foam concrete roof can be purchased at a retail chain when large volumes need to be poured. Otherwise, you can rent it for one-time work.

List of required equipment and tools for a foam concrete roof:

1. 
   Concrete mixer with a volume of at least 300 liters.

2. Compressor for supplying compressed air to the foam generator.
3. Concrete pump for supplying mortar to height.
4. Ready-made removable formwork with telescopic supports.
5. Measuring containers to maintain the proportions of the solution.
6. Buckets.
7. Mortar shovel.
8. Extended rule.
9. Personal protective equipment: gloves, safety glasses and a respirator.
10. Specialized roofer's tool.
11. Gas burner for rolled material.
12. Foam generator for producing foam. This is a device in which air, water and a foaming agent are mixed.

The maximum permissible volume of foam is set at a ratio of 1.5 liters per 1 m3 of foam concrete. If this ratio is exceeded, the hardening time increases and the strength of the finished roof base deteriorates.

Advantages and specifics of using foam concrete

Foam concrete is widely used for insulating the roof of a private house. It is relatively lightweight, does not rot or mold, and does not attract rodents.

Rigidity, uniformity and stability of geometric parameters prevent the roof from pushing through and the formation of recesses - moisture collectors. Using foam concrete as insulation does not require significant labor costs.

The thermal conductivity of foam concrete is lower compared to other insulation materials. The thickness of the material layer is determined by thermal engineering calculations and, depending on the climatic zone, is 30÷150 cm.

The disadvantages of the material include poor breathability, which prevents air circulation. Foam concrete contains toxic foaming agents, and therefore cannot be used to insulate a house from the inside.

Properties and characteristics of the roof

Since the foam concrete roof performs several protective functions, it must be strong and durable, must have the appropriate properties and meet the following characteristics :

1. Moisture resistance - requires increased moisture protection of the “roofing cake”.
2. Fire resistance - non-flammable and does not spread fire.
3. Frost resistance - not lower than F35.
4. The service life is no less than that of wall structures and the total service life of the building, more than 50 years, with the replacement of the soft roof after 15-25 years, depending on the type of external covering and the composition of the “roofing pie”.
5. The optimal type of drainage is chosen depending on the climatic characteristics of the area: external systems in the southern regions - water is discharged through pipes placed externally along the perimeter of the building or through gutters fixed at the bottom; in the northern and middle climatic zones - the internal sloping drainage system diverts water to water intake points in the center of the roof, and then through insulated pipes into the intra-house sewer system.
6. Optimal drainage slope: 1-4%.
7. For middle and northern climatic regions, roof water intakes must be heated.
8. The thickness of the screed for soft insulating material is 25 mm, for hard insulation - 15 mm, for bulk thermal insulation - 40 mm with steel reinforced mesh.
9. Ventilation system for roofing cakes made of bitumen and bitumen-polymer materials - arrangement of wind vanes over the total area, the pitch is determined by the composition of the “roofing cake”.
10. The foundation of the house and the load-bearing capacity of the walls must support the weight of the foam concrete roof.
11. When the building height is over 10 m, a parapet must be installed on foam concrete roofs, and for those in use, the parapets must be at least 1.2 m high. For a roof that is not in use and a one-story cottage, fencing bars can be installed instead of a parapet.

Main stages of technology

The flat roof structure includes layers:

• load-bearing base: reinforced concrete structures, profiled metal sheets;
• vapor barrier: film or built-up materials;
• insulation (foam concrete);
• waterproofing: roll, mastic or other materials;
• roofing material.

The surface for pouring foam concrete does not need to be leveled - the material fills all the recesses. Before pouring, the roof is covered with a vapor barrier, divided into segments and formwork is installed along their boundaries. The “concrete dough” is supplied to the roof with a hose from a special installation located on the ground. Foam concrete has a density of 250÷350 kg/m3, it provides insulation and the required roof slope. The solution is allowed to harden, then the top protective layer (screed) with a density of 500÷600 kg/m3 is poured for high-quality waterproofing stickers.

• How to lay flexible tiles on the roof?

• How to properly lay a vapor barrier on the ceiling?

• Is it possible to glue wallpaper on whitewashed walls?

There is no need to install a concrete screed on a foam concrete roof. Then, 10 days after pouring, the surface of the insulation is covered with a primer, waterproofing is glued or fused, and roofing material is laid. In this case, a single monolithic layer combines insulation and screed, which reduces labor costs and the cost of work.

The cost of roof insulation with wood insulation from Vazhny Dom LLC

The exact cost of the work can be determined after consultation with our specialists.

Free consultation with a specialist

and calculation of the cost of roof insulation

by phone:

When is it advisable to equip?

This type of roof is preferable for installation in special climatic regions. It does not require a rafter frame and rests directly on the load-bearing walls, so it tolerates almost any wind load well, but at the same time poorly copes with snow loads and water drainage from the roof. Therefore, according to climatic characteristics, it is preferable in arid areas with strong winds.

The construction of a foam concrete roof depends on the design solution and the nature of use; it can be installed as :

1. Unexploited, which is used only for repair and restoration work.

   Advantages: simplicity of device, light weight, low cost per 1 m2, long service life, good repair potential, wide range of applications from country houses to high-rise buildings for residential, industrial and public purposes.

   The disadvantage is a reduction in the amount of usable space in the building.

2. Exploited with a slope of up to 2 degrees, ensures the constant presence of people, can be used for parking, swimming pools and recreation areas.

   Advantages: used for permanent occupancy of people, increasing the usable area of ​​the building, wide areas of application from private large cottages to multi-storey buildings for public, commercial and industrial purposes.

   Disadvantages are significant cost and high requirements to ensure high reliability of load-bearing wall structures.

3. Inversion, differs from a conventional flat roof by the reverse order of the roofing pie: the waterproofing is swapped with the insulation.
   Advantages: simplicity of device, low weight, low cost per 1 m2, highest protective functions, high service life and repair potential, wide range of applications.

   The disadvantage is a reduction in the amount of usable space in the building.

The foam concrete roof can be ventilated with the installation of aerators, attic or non-attic. These types have their advantages: the existence of an attic makes it possible to place all the necessary utilities on it, and a non-attic structure can possibly be made operational.

What buildings is it suitable for?

In modern construction, both civil and industrial, developers erect flat foam concrete roofs quite often. This is due to the cost-effectiveness, ease of installation and maintenance of the structure.

Experts believe that
it is most promising to install foam concrete roofs on the following buildings:

• infrastructure facilities;
• terraces of private buildings;
• high-rise condominiums;
• public buildings;
• industrial building;
• shopping centers;
• wine cellars;
• educational establishments;
• buildings of logistics companies;
• medical institutions.

Wall materials

Installation of foam concrete roofs requires the presence of powerful load-bearing walls. They must be carried out in accordance with applicable government regulations and rules. The most important of which is the norm for supporting a foam concrete base on load-bearing walls, established by SNiP for different materials.

The norm for supporting a flat roof structure made of foam concrete during installation is the standard amount of overlap on load-bearing walls, the optimal value is 120 mm.

Types of wall materials for foam concrete roofs with support depth:

• large-format concrete blocks of a grade not lower than M 200 - 90 mm;
• brick -120 mm;
• low-strength blocks gas silicate and foam block -150 mm;
• steel load-bearing elements - 70 mm;
• stone walls - up to 150 mm.

In cases where it is impossible to ensure the optimal amount of support, specialists must clarify the minimum indicator taking into account all types of operating loads: seismic resistance of the area; roof parameters; height of the building; load-bearing wall thickness; the presence of heat-insulating and facing building materials in the “wall pie”.

Specifics of using foam concrete for insulating roofs of country houses

A flat roof can expand the usable space of a country house and become an attractive place to relax. On it you can arrange a cozy gazebo, sports ground, swimming pool and even a mini-golf course. For a roof in use, a rigid roof insulated with foam concrete is suitable.

An important requirement, especially for country houses, is the installation of a heated cleaning system, which melts snow on the roof, and maintaining the required slope ensures unhindered water flow.

Foam concrete does not create excess pressure on the structures of a private house, and therefore its use is possible even on wooden floors. The convenience of roof insulation with foam concrete also lies in the durability of the material - when repairing the roof, only the top roofing carpet is replaced. The components of the insulation solution are available and inexpensive.

Find out the advantages and disadvantages of other insulation materials:

Which insulation is better for roofs of different designs?

The construction of a residential building roof is often accompanied by the need to insulate it. Modern industry produces a large number of sheet and roll heat-insulating materials. Which insulation is better for a roof and what parameters should you use to choose it? All owners involved in individual housing construction or renovation of their home would like to know the answer to these questions.

The choice of roof insulation depends on the type of roof structure and the preferences of the homeowner

Characteristics of various types of insulation

Modern insulation materials are of mineral and synthetic origin. Both have their pros and cons, which are worth examining in detail. The most used materials for thermal insulation today are:

• mineral wool;
• Styrofoam;
• sprayed polystyrene foam;
• foam glass;
• foam concrete;
• bulk insulation materials.

When laying insulation, it is recommended to use protective equipment: a respirator and gloves

To understand which of the listed insulation materials is best for a roof, you need to know their characteristics.

Mineral wool

This insulation comes in basalt and glass. In the first case, the composition contains rock chips, which means adjusting the acidity of the material. This parameter greatly influences moisture resistance in direct proportion. Glass wool is made from broken glass, which makes it durable and very elastic. It is a fire-resistant material that can withstand temperatures of 400 degrees.

Mineral wool - lightweight and inexpensive roof insulation

Advantages of mineral wool: excellent thermal insulation qualities, low weight, environmental friendliness and low cost. This material also has disadvantages: the need to construct a thick layer of up to 25 cm, which reduces the useful volume of the attic space, the unpleasant effect of glass dust on the skin and respiratory system during installation. This material is produced in slabs, rolls and mats.

Helpful advice! For high-quality insulation of floors or roof truss systems with mineral wool, you need to wrap it around all the rafters and lay the material between them. A film vapor barrier is made on top of the mineral wool.

Roof insulation from the outside using sprayed polystyrene foam

Polystyrene foam and polystyrene foam

This material is a slab of foamed synthetic substance - polystyrene. Since this substance itself is quite flammable, during the production of insulation, special additives are added to the composition to stop combustion. Among the advantages we can note: resistance to rotting, poor thermal conductivity, very low weight. Among the disadvantages, experts highlight only poor sound insulation and low strength, which is not critical when insulating the roof.

Polystyrene foam is an excellent material for roof insulation.

If, when deciding which insulation is best for a roof, the choice is made of polystyrene foam, then you need to know some of the features of its installation. When insulating, it must be placed with a heat-reflecting surface to the rafters. The sheets must be securely fastened with anchors, since loose foam can make sounds from the wind. It is advisable to lay the polystyrene foam in a double layer, overlapping the seams and cover it with plasterboard on top.

Expanded polystyrene differs from polystyrene foam in its higher strength

Separately, it is necessary to note such material as sprayed polystyrene foam. The technology of its installation is completely different. Using a special device, the polystyrene mass is sprayed over the surface. Possessing fluidity, it penetrates into all cracks and irregularities, filling them. Under the influence of air, the mass foams and hardens. This type of insulation is the most convenient to install and has all the advantages of polystyrene foam. The disadvantages include the high price and the need to use a special installation.

Special equipment is used to spray liquid polystyrene foam

Foam glass

This material is obtained by heating silicate glass above 1000 degrees. This temperature causes a foaming effect in it. Foam glass slabs, blocks and granules are used as effective insulation. It can withstand temperatures ranging from -260 to 500 degrees. This is a completely environmentally and hygienically safe material.

Foam glass is an excellent insulator and completely environmentally friendly

Positive qualities of foam glass: great strength, lack of tendency to shrink. It does not burn and does not freeze, and is not susceptible to acids and alkalis. Fungi and bacteria do not settle on this material. No other thermal insulation material has such a number of useful properties. The technology for laying foam glass is very simple and no more complicated than that of foam plastic.

Foam concrete

The material from which foam blocks are made is light enough to withstand floors, strong and durable, and has recently become widely used in the construction industry. It is especially in demand in industrial construction. It has good thermal insulation properties and excellent sound insulation.

Roof insulation with self-leveling foam concrete

Bulk insulation materials

These include expanded clay, sawdust, shavings and other similar materials. Today, few people use them in construction, since in addition to positive qualities they have a lot of negative ones: shavings and sawdust give rise to dampness and fungus, expanded clay is too heavy for light floors, and cannot be used in attic roofing. The main advantage of such insulation materials is their low price, which allows them to insulate the roofs of some outbuildings, especially in rural areas.

Helpful advice! When using insulation on the floors, it is necessary to lay a film vapor barrier. This will prevent the ceilings from leaking in the spring when condensation melts under the roof.

Granulated polystyrene foam is used as bulk insulation

Roofs and flat roofs made of monolithic foam concrete.

The basic design of thermal insulation for modern flat roofs.

Table 1. Comparative thesis justification for the choice of flat roof design.

Shrinkage during use.

Foam plastics and mineral wools decrease in size during operation, especially under load from the overlying layers of the roof. At the same time, the roofing “pie” slides down, tearing the waterproofing away from the parapets.

In addition, due to the unevenness of the snow load, mechanical loads (people walk on roofs along certain paths, and not uniformly along the entire roof), due to the heterogeneity of the insulation material itself and the uneven thickness of the mortar screeds in traditional roofs, the formation of depressions in the planes of the roof, the so-called lenses, occurs where water accumulates. The roof becomes “lumpy” over time. In places where “lenses” form, the screed is usually broken, and at the slightest violation of the tightness of the top layer of the roofing carpet, water from the lenses enters the roof. In roofs made of foam concrete, the formation of “lenses” and depressions is impossible even if people are constantly on the roof, since foam concrete is a rigid and durable material.

Compressive Strength

Mineral wool and foam plastics, including extruded ones, do not have compressive strength. They are characterized by load values ​​during deformation. This indicator gives us a strength value that shows the material being 10% compacted. Those. in an uncompressed state, neither mineral wool nor foam plastics are able to resist the load.

Strength at 10% deformation of mineral wool with a density of 100-150 kg/m3 and extruded foam does not exceed 300 kPa (0.3 MPa). The strength of foam concrete with a density of 200 kg/m3 starts from 0.3 MPa (300 kPa). Those. foam concrete can withstand the same load as mineral wool or extruded foam when compressed by 10%. But under such a load, foam concrete does NOT deform.

Water absorption of foam concrete.

Most thermal insulation materials used on roofs have high water absorption. 60% of thermal insulating roofing materials are represented by various types of mineral wool, the actual water absorption of which is up to 70% by volume (1500% by weight). This figure exceeds the water absorption of foam concrete by one or even two orders of magnitude.

State standards do not regulate the water absorption of mineral wool, since it is understood that this material should only work in conditions where there is a complete lack of ability to absorb water. Naturally, in practice, under the conditions of a real construction site, this is impossible - both during the period of work and during operation. Also, practice shows that it is almost impossible to dry soaked mineral wool, especially in the conditions of the lower layer of the roofing cake, which cannot be ventilated.

The situation with water absorption is slightly better for polymer foamed plastics, including the highest quality of extruded polystyrene foam achievable today. Despite the low “paper numbers” for water absorption by foam plastics, we forget that on top of the foam plastic there is material for creating roof slopes. In most cases, this is the cheapest bulk material - expanded clay, on top of which a cement screed is made, or sheet materials are mounted (asbestos-cement sheet, cement-bonded particle board, etc.). By the way, exactly the same roof construction is made using mineral wool slabs. But in this case it is not so important, due to the already huge water absorption of mineral wool.

The layer of bulk expanded clay has a thickness of 50 to 400 mm and is a cavity under the screed that can absorb from 25 to 200 liters of water per square meter! Moreover, in the event of a leak through the screed, the leak into the building may be located at a distance of tens of meters from it, finding a free path in the expanded clay layer. Detecting damage to roof waterproofing is extremely difficult. (See Fig. 5.)

A roof with monolithic foam concrete behaves completely differently. Particularly lightweight foam concrete is completely protected from water leaks by a layer of structural “screed” foam concrete, which absorbs water to a depth of about 10 mm. If the waterproofing is damaged, the foam concrete mass can stop the movement of moisture deeper into the roof. It should also be noted that the remarkable fact of self-drying of foam concrete is that water trapped inside the foam concrete mass is used by the cement matrix of the material to continue hydration reactions that occur with the chemical binding of free moisture. The hydration reaction compacts the foam concrete structure and stops further movement of moisture. In case of serious damage to the roofing carpet, the roof hardens locally - only at the site of damage, and not under the entire surface of the screed, as when using expanded clay to create slopes over foam plastic and mineral wool.

Flammability

Foam plastics burn well - thanks to numerous fires, citizens farthest from the construction industry know about this. The burning of foam plastics is accompanied by the release of toxic gases, which, however, occurs not only during combustion, but also with the slightest increase in temperature. One drop of welding when performing lightning protection on the roof, and a fire is more than likely, even during the construction period of the building.

Mineral wool does not burn, but smolders. Smoldering is ensured by a phenol-formaldehyde binder. Naturally, when burning, nothing good will be released into the atmosphere either.

Foam concrete is a foamed stone, and stones do not burn. On the contrary, foam concrete can be used as fire protection, for example, for metal structures.

Roofing pie design.

The design of a modern flat roof consists of several elements. As we already described in the “water absorption” section, these are three layers:

— a layer of thermal insulation (mineral wool or polystyrene foam);

— a layer forming the slopes of the roof towards the drainage funnels (expanded clay gravel);

— screed (cement-sand mortar with reinforcing mesh or sheet materials).

In the case of using monolithic foam concrete, the thermal insulation layer and the slope-forming layer are made of monolithic, extra-light foam concrete with a density of 200 kg/m3, which significantly increases the thermal protection of the roof. The screed on top of this layer is also made of foam concrete, only more durable and dense, with a density of 500 kg/m3.

Naturally, homogeneous materials, due to their affinity, work better both in thermal and structural terms. There are no dips, peelings, bubbles or other defects on the roof that are so common with traditional roofs.

Features of the roof structure

When making a layer of thermal insulation from slab material, difficulties always arise when performing thermal insulation of complex architectural elements on the roof, in places where communications pass (electrical wiring, ventilation, sewerage, etc.), places for installing building equipment on the roof (air conditioners, etc.). Accurate cutting of slabs is labor-intensive and practically difficult to control. As a rule, all these places will have problems with freezing and getting wet in the future.

Monolithic foam concrete fills all the voids in the roof, forming a continuous warm shell of the building, monolithizing the roof. By definition, the problems described above with traditional roofs do not arise.

Roof durability

Both expanded polystyrene and mineral wool (which contains a polymer binder), like any other polymer material, are subject to destruction during operation. Especially in extreme roofing conditions associated with overheating and often moisture.

Hundreds of books and articles tell us that any polymer has a limited service life. This is especially true for thermal insulation polymers.

Foam concrete, like any concrete, only gains strength during use. Our own research shows that foam concrete, which has a strength of 0.3 MPa at the age of 28 days, will strengthen to 0.5 - 0.7 MPa after a year of operation. Let us recall that hardening occurs when free moisture in the material is bound, due to which the foam concrete self-dries, even in sealed conditions.

Building load

Roofs made of monolithic foam concrete are lighter than traditional roofs, which in some cases makes their installation a non-alternative option, especially when carrying out reconstruction work.

Table 2. The weight of a traditional roof insulated with polystyrene foam.

Table 3. Weight of a roof insulated with monolithic foam concrete.

Please note that monolithic foam concrete allows slopes of a smaller degree than traditional roofs with expanded clay screed.

Defects in roofing carpet.

The most common defect of a traditional roof is the presence of swellings on the roofing carpet when it is heated in the summer. This occurs when water vapor under the waterproofing layer is heated. Foam concrete roofs are practically free of defects of this type, since the excess pressure of water vapor is evenly distributed in the pore space of the foam concrete. The mechanism of this phenomenon is discussed in more detail in our article “Buffer foam concrete screeds in the reconstruction of flat roofs” in the magazine “Building Materials” for November 2012.

Appendix 1. Work in winter conditions

The main disadvantage of roofs with monolithic foam concrete is the limited possibilities for winter work. Industrial production of foam concrete is possible at positive temperatures, for a combination of reasons - the main one being freezing of water supply hoses. In addition, we fundamentally do not recommend performing roofing work in winter conditions, also for a number of reasons:

• Excessive consumption of gas for removing ice and snow;
• Overspending on wages for removing ice and snow;
• Inability to control the absence of snow and ice inside roof structures;
• Excessive consumption of gas for sticking the waterproofing layer;
• Damage to materials and equipment due to frost.

However, it should be noted that the technology allows work to be carried out at temperatures down to -7 degrees.

Appendix 2. Polystyrene concrete as insulation.

The use of polystyrene concrete on roofs is most often unjustified for economic reasons, since polystyrene foam granules, which are filler, are most often unreasonably expensive.

At the same time, there are additional negative circumstances that must be taken into account when working with this material. Polystyrene granules decrease in size during operation. As a result, after a year or two, instead of polystyrene concrete, we get large-porous concrete with expanded polystyrene chips. As a result, the strength and thermal conductivity of polystyrene concrete sharply deteriorates. The photos below show a polystyrene block at 5 years old.

Which insulation is best for a roof: selection criteria

Most insulation materials are designed for any surface. All of them cope with the task of insulation perfectly if laid correctly. Which insulation is best for a roof is a matter of taste rather than technical features. Therefore, most consumers choose the one that they can afford. In addition, you also need to take into account the convenience of installing a separate insulation on a specific type of roof. For light floors, polystyrene foam, polystyrene foam and mineral wool are best suited. These materials are very light in weight, which allows for multi-layer coating.

Expanded clay - an affordable and environmentally friendly bulk sealant

Insulation of floors begins with laying a vapor barrier film. It is already necessary to lay several layers of insulation on it, depending on the climatic conditions in a particular area. All joints must be filled with foam.

Related article:

Do-it-yourself roof insulation from the inside, types of insulation materials and technology. Review of insulation materials and preparation for work. Technology of roof insulation with sheet material, liquid foam.

In order to insulate the roof from the rafter side, it is necessary that the roofing material be laid on top of the vapor barrier. If insulation is done during the process of changing the roof or new construction, then it is more convenient to do it even before installing the sheathing. For this, a double crate is made. The first layer of boards or plywood is placed on the bottom surface of the rafters. Insulation and vapor barrier are already installed on them. Then the main sheathing is made and the roofing material is laid.

Roof installation with insulation

If insulation is done when the roof is finished, then all work is done from the attic side, which is less convenient, but still effective. The slabs or mats are attached to the sheathing and rafters, and then covered with a vapor barrier and drywall or plywood.

Especially it is necessary to say about insulation for attic roofs. Which insulation is better in this case depends on several factors.

Installation for spraying liquid polystyrene foam

How to calculate the quantity?

In order to calculate the volume of foam concrete to create a roof, you will need to know the design grade, the overlap area and the thickness of the base layer. Depending on the roof design, the base layer is taken from 100 to 200 m.

Standard composition of the mixture by weight depending on the brand:

1. Foam concrete grade - D400/D600.
2. Sand - 0.15/0.21 t, price - 300 rub./t.
3. Cement M500 - 0.30/0.31 t, price - 5000 rub./t.
4. Water for diluting the mixture - 115/115 l.
5. Water for diluting the foaming agent - 60/55 l.
6. Foaming agent - 1500/1300 g - price - 140 rub./l.
7. The pore volume in the finished foam concrete is 85/75%.
8. Foam concrete yield - 0.47/0.68 t.
9. The volume of foam concrete is 1.1/1.1 m3.

Initial data for calculating D400:

1. Roof dimensions: thickness - 150 mm; length - 10 m; width -10 m.
2. Characteristics of the fittings: length and width of the cell - 400x200 mm; D-6 mm; number of rows - 2.
3. Board for formwork: thickness - 25 mm; length - 6 m; width - 100 mm.
4. Composition of foam concrete: cement in bags - 50 kg, per 1 t - 20 bags, per 1 m3 - 7 bags.
5. Proportions of foam concrete by composition: cement - 0.30:0.47=0.63; sand - 0.15:0.47=0.31; foaming agent - 0.0015/0.47=0.0031.
6. Cost of building materials: cement - 250 rubles/bag; sand - 300 rub./t; foaming agent - 140 rub./l; board - 5500 rub./1 m3; fittings - 20,000 rub./t.
7. The roof area is measured - 10x10m.

Calculate the volume of foam concrete for pouring the roof:

• Slab area: 100.00 m2.
• Volume of foam concrete for the roof: 100x 0.15 = 15.00 m3.
• Calculation of reinforcement for rows: horizontal - 26 pcs.; vertical - 51 pcs.; total length - 1540 m; total weight - 341.88 kg.
• Formwork area: 6.00 m2.
• Lumber: 0.15 m3 or 10 pieces = 6: (6x 0.1).
• Construction materials: cement 50 kg in bags - 105 pcs. or 5250 kg.
• Cost of cement: 5250x5000=26250 rub.
• Sand: 1.8375 t x 300 = 551 rub.
• Foaming agent: 1.1x15= 15.75 kg.
• Cost of foam concentrate: 140x15.75= 2205 rub.
• Board: 0.15 m2 x 5500 rub. = 825 rub.
• Reinforcement: 341.88 kg x 20000 = 6838 rub.
• Total cost of the foam concrete base = 36,684 rubles.