Warming of flat roofs

Flat roofing is an inexpensive and practical way of building any structure. Often it is erected over multi-storey residential buildings, industrial facilities, garages and outbuildings( verandas, terraces).In the case of residential buildings, a flat roof must necessarily be insulated, otherwise there will be little help from it. This is what we will talk about in today's article - the insulation of a flat roof with our own hands.

Insulation features

The need for roof insulation, including flat, is obvious - anyone familiar with the concept of convection from the school coursephysics, should understand that the air, heating up, rushes up. If at the top he does not meet a worthy barrier, he will leave the premises unhindered. In other words, all efforts to heat the house under a flat roof are reduced to nothing.

However, the useful side of roof insulation does not end there. In addition, that the thermal insulation detains warm air, it prevents the occurrence of sharp temperature changes inside the roof cake. Let us turn to the same school course of physics. When cold outdoor air collides with heated streams rising from the house, the reaction generates condensation - the smallest droplets of water. Accumulating, condensate impregnates layers of roofing cake and wooden elements, provoking their rapid wear. For this reason, the installation of a heater alone under the roof covering is indispensable - it is necessary to protect it with a vapor barrier membrane that will remove condensate from the thermal insulation and promote its rapid evaporation.

It turns out that the device for the insulation of flat roofs implies the use not only of thermal insulation material, but also vapor barrier. The order of installation depends on the type of roof. Flat roofs are classical and inverse. In the first case, the foundation is the carrier plate, which is laid vapor barrier, and then the insulation. It, in turn, is closed with a roll-on waterproofing based on bitumen. It simultaneously protects the heater from moisture and is the finish coat. Such roofs can be found on multi-storey buildings in any city. It is also worth mentioning that the classical roof can be exploited and unexploited. As you can see from the name, the roof can be used, that is, to have equipment, furniture, make superstructures, in general, use it fully as an additional surface. The covering of the unexploited roof is not adapted to the increased loads, but the insulation by both types passes under identical scenarios.

Inverted roof in technical performance is much more perfect than traditional. First, a layer of gravel, expanded clay or gravel is poured onto the carrier plate. The thickness of the powder should be at least 5 cm. On such a drainage pad put waterproofing, then a heater, pour all with concrete and cover the screed with the finish material. The main difference in the laying of insulation over waterproofing, which allows you to protect the hydrophobic layer from harmful ultraviolet rays, temperature changes and mechanical damage. As a result, the inversion flat roof serves a lot longer traditional and automatically becomes operational - a strong concrete screed( especially if it is reinforced) allows you to arrange recreational and outdoor sports grounds.

It should be taken into account that different types of loads will be applied to the insulation, as on all other layers of the roofing pie: snow weight, wind force, weight of overlying materials, etc. Therefore, to insulators for flat roofs, there are increased physical and mechanical requirements. In addition, experts strongly recommend choosing the most hydrophobic material, since it is impossible to guarantee 100% protection from moisture. More about the choice of insulation we'll talk about later.

Methods for the insulation of flat roofs

The insulation of flat roofs is carried out according to one of two schemes: in one or two layers. Single-layer insulation is important for industrial buildings, garages and warehouses. Suitable for exploited and unexploited roofs( in the first case it is necessary to have a reinforced concrete screed with a finishing coat).The placement of a heater in one plane gives a moderate protection against the appearance of condensation and excessive heat loss, but to create a comfortable microclimate for a cozy life allows only two-layer insulation.

Two-layer thermal insulation scheme, as you might guess, involves the laying of two layers of thermal insulation material in different planes. The lower base layer should be thermally stable at low strength and thickness from 70 to 170 mm. The upper layer is responsible for distributing the mechanical load over the entire surface of the system. Its thickness is much smaller than that of the lower layer, and is 30 to 50 mm, but it has a high compressive strength and a rupture strength. Such a functional distribution of two layers of insulation significantly reduces the weight of the roofing cake as a whole, thereby reducing the load exerted by the roof on the floors and foundation.

The choice of insulation for the roof

For the insulation of a flat roof from outside use a variety of materials, but after studying the above information, we can already identify a few basic selection criteria. First, the maximum hydrophobicity. Secondly, strength and density. Third, if possible, a little weight. Consider the materials used in modern construction.

Most often urban and private construction uses backfill materials because of their availability and low cost. It's about expanded clay( high-pressure expanded clay) and perlite( light coarse-grained sand with good thermal insulation characteristics).Unfortunately, the low cost and availability of the dignity of these materials are limited - on other parameters they are not able to compete with fibrous or polymeric insulation. They are relatively heavy, and to create with their help a perfectly flat surface under a slight slope is rather difficult.

The second most popular are mineral wool boards and expanded polystyrene. Mineral cotton wool keeps the heat well, it is convenient to work, does not burn, but it needs a high-quality waterproofing - if it gets any wet, it will stop protecting against heat loss. Extruded polystyrene foam is not afraid of water, it has high strength, easy installation and relatively low cost. However, it is better to use it to create an inversion roof, since the material is very sensitive to ultraviolet radiation and is inflammable.

. Not so long ago in the market there was a mineral wool in plates, made of basalt rocks. It is much stronger for compression and rupture than older analogs, not so much afraid of water and allows you to create a sufficiently strong coating without the arrangement of a heavy concrete screed.

Finally, the newest, high-quality and expensive insulation is polyurethane foam. A special composition is applied to the prepared surface by the method of mechanical spraying, after which it foams, hardens and creates a strong waterproof crust that perfectly retains heat and is impervious to ultraviolet radiation. In the West, polyurethane foam has long been used for insulation of roofs, including flat roofs. In our latitudes, its advantages have only just begun to be appreciated.

Positive aspects of using polyurethane foam for roof insulation:

• very low thermal conductivity( polyurethane foam 0.022 W / m², min. 0.055 W / m²);
• requires minimal preparation of the surface( clear of debris, can not be leveled and not treated);
• for a good thermal insulation is sufficient for a layer 5-6 cm thick;
• absolutely seamless coating, which eliminates the formation of potentially risky leaks and drafts;
• absolute hydrophobicity and vapor tightness( allows to save on hydro and steam insulation);
• spraying can be used to create additional waterproofing;
• high rigidity of the frozen coating allows you to build a concrete screed over it;
• is relatively low density( does not give a strong load on the bearing elements);
• environmental safety;
• possibility of covering surfaces and objects of any shape( it helps to protect the problematic exit points of pipes from leaks and heat losses);
• does not burn and does not support combustion;
• service life is more than 25 years;
• high speed of work.

Thus, polyurethane foam replaces both insulation, and steam, and waterproofing. The only drawback is that you can not do this with your own hands, because this requires special techniques and skills for handling two-component material.

Thermal insulation technology

It's time to tell how to insulate a flat roof yourself. Since the disadvantages of loose insulation do not allow talking about them, as the best options for the arrangement, we will touch on the use of mineral wool boards and extruded polystyrene foam.

Mineral wool plates

Immediately make a reservation that not every mineral wool board can be used to insulate a flat roof or a classic soft roof. The best for this purpose are basalt slabs, the fibers in which are directed in different directions - this allows them to withstand high loads. Of course, it is possible to protect the fragile insulation with a screed( dry or wet), but this will create additional stress on the supporting structures.

Mineral wool insulation technology:

1. The basis for laying are reinforced concrete slabs or metal profiled sheets.
2. Regardless of the type of base before laying the insulation, it is covered with a vapor barrier membrane. If we neglect this moment, in time, the mineral wool plates become impregnated with condensate and cease to retain heat, and the waterproofing laid on top of them will be decorated with "blisters".Steam insulation membranes are one- and two-sided. In the first case, a space of 3-4 cm should be left between the membrane and the base, so that the condensate can evaporate freely. When using a double-sided diaphragm, the ventilation pocket is not necessary. As an alternative to membranes, you can use conventional building polyethylene or welded materials( bitumen, polymer bitumen).As a result, the vapor barrier must close all horizontal and vertical planes, and the coating should be started just above the level to which the heater will reach.
   
3. Mineral wool slabs should be laid in one or two layers. In the second case, you need to calculate the thickness of the future roofing pie in advance and, if necessary, strengthen the insulation with a layer of thin and high-strength slabs. Usually this is done in the northern regions, where the humidity level and temperature fluctuations are so great that it disables conventional heaters.
4. To the base plate attached telescopic dowels or glued to bitumen - the method depends on the type of base. It is better to use dowels for the profiled sheet, but for concrete slabs they will do, however, the fasteners for concrete are more expensive than for metal. If you prefer a mechanical fixing method, the vapor barrier must be fusible. To glue a heater to bitumen is rather troublesome and expensive, but this method is recommended for insulation of roofs with concrete bases. A bitumen layer is applied to the surface and the plates are glued to the butt. If you want to create a second layer of insulation, the bitumen is smeared with the surface of the first layer and pasted on it additional slabs "in the run"( so that the joints of the second layer do not coincide with the joints of the first).
5. If the insulation was fixed mechanically, then the waterproofing on top of it should be fixed in the same way, that is, using dowels.

Video on the insulation of a flat roof with mineral wool:

Extruded polystyrene foam

Extruded polystyrene foam has a high strength and water resistance, and therefore is most often used for insulation of inversion roofs. On the slabs there are slit locks, which provide a very dense surface, but for a greater reliability of all joints it is recommended to glue with adhesive tape.

The beauty of expanded polystyrene is that it is very simple and fast to work with:

1. First, slabs are laid on the base plate, gluing the joints with construction tape. If you want to lay the second layer, the plates are mounted "in a runaway".
2. Over the expanded polystyrene insulation lay geotextile, designed to protect the lower layers of the cake from dirt and mechanical damage.
3. Add 5-10 cm of gravel or crushed stone to the geotextile. Sometimes a profiled membrane is placed for additional drainage between the geotextile and the powder.
4. Finally, the rubble or gravel is poured with a screed and laid the finish coat. If it is planned to plant lawn grass or flowers on the roofed roof, an additional layer of geotextile should be laid on top of the backfill, after which 15-20 cm of fertile soil should be poured.

To heat a flat roof is not so simple, but this measure is relevant if you want to live in a warm house and do not overpay for heating.