When building a country house, as well as various buildings on the site, sooner or later the question arises of how exactly to make a roof for it, since there are a lot of options. This article discusses one of the types of roofing, namely, a do-it-yourself flat roof, since this type of roof device has recently gained serious popularity.
Before talking about how to make a flat roof, it should be noted that in construction the concepts of "roof" and "roof" have completely different meanings.
The roof includes all the contents of the space above the living spaces, and the roof is just the top covering of the roof, exposed to precipitation and sunlight.
Knowing this division of concepts, we can conclude that projects of country houses with a flat roof are usually designed to work alone only if the area of the future roof is small, and the independent installation of a flat roof of a serious area requires at least several assistants.
What is a flat roof
With a relatively small amount of construction, for example, a garage, a barn, or even a small one-story house with a flat roof, it is quite possible to complete the work without inviting qualified specialists.
First of all, on the load-bearing walls of the building, wooden or metal beams should be installed, which will transfer the main weight of the roof to the foundation and load-bearing walls.
In addition to the own weight of the roof, the beams must also withstand additional loads on it, such as:
- The total weight of the roof structure and communication elements located in the attic and directly on the roofing;
- The weight of a person repairing or servicing a roof or roof;
- The weight of snow, combined with wind pressure in winter, is the main load on a flat roof due to the lack of a slope.
For a more correct choice of load-bearing beams and determine the load that they must withstand, you can use the experience of neighbors, for example, by studying how one-story houses with a flat roof are built in adjacent areas.
To make a high-quality flat roof, it is necessary to choose the right coating with sufficient reliability, as well as high-quality roofing materials with good performance parameters.
In addition, the most important is the correct and competent performance of work, such as vapor or waterproofing of a flat roof.
In capital buildings, flat roofs are usually made of lightweight floor slabs, on which a “pie” of insulating materials is laid in several stages:
- First, a vapor barrier is laid to prevent the penetration of moisture from the room into the insulation. Vapor barrier is made in the form of a polymer-bitumen film reinforced with fiberglass, glued to a concrete screed. The edges of the film should be brought behind the vertical overlaps, and all seams should be carefully soldered.
- Next, the heater is installed. If expanded clay is used for insulation, then it is first necessary to cover it with a concrete screed, and in the case of arranging a lightweight version of the roof, a solid polymer insulation is glued directly to the vapor barrier layer.
- The most important layer is the flat roof waterproofing or "pie" as this layer is often referred to. Usually it is made of membrane or polymer-bitumen materials.
Flat roof for unheated rooms
When constructing an unheated structure, such as a gazebo, a shed, etc., a slope for rainwater runoff can be created by tilting the roof surface.
To do this, it is possible to install load-bearing beams under a slope, on top of which a solid shield made of boards is laid, covered on top with a roofing felt rolled carpet.
The rolled carpet is attached to the shield using slats or metal strips, which are nailed along the slope at a distance of 60-70 centimeters from each other, without creating obstacles for water to drain. In this case, the slope should not be less than 3%, which is 3 centimeters per linear meter of length.
Flat roof for heated rooms
In the event that the building under construction is heated, the flat roof equipment takes place in several stages:
- The laid beams are covered with a flooring of boards, on top of which the roofing felt or roofing material is dry laid, the overlap of the strips should be at least 15 centimeters.
- On top of the roofing material, insulation made of expanded clay, slag, etc. is backfilled, when falling asleep, a slope should be observed in the direction of discharge of rain and melt water from the roof.
- A cement screed is made on top of the insulation layer, the thickness of which should be at least two centimeters. After setting the screed, it is treated with a bituminous primer.
- A rolled carpet is glued over the screed.
The greater the span of the roof (the place between the places where the beams rest), the more difficulties arise related to how to build a flat roof, so roofs over six meters wide are not recommended to be made independently.
If the width of the roof does not exceed 6 meters, either a wooden beam with a cross section of 15x10 cm or an I-beam made of metal is used for it, the distance between the beams should not exceed one meter.
Such subtleties are very important, because even if you do
Flat roof made of monolithic concrete
The load-bearing structures for the installation of a monolithic concrete roof are I-beams.
With a roof span of 4-5 meters, beams are used, the height of which is 12-15 centimeters, or, in the language of builders, “the twelfth or fifteenth I-beam”.
For a monolithic slab, it is best to purchase ready-made concrete of grade 250; if it is made on site, it is recommended to use a concrete mixer, since it is almost impossible to manually achieve the desired degree of mixing.
For the manufacture of concrete of this brand, crushed stone with a fraction of 10-20 mm and cement of the PC 400 brand are used. These ingredients are mixed in the following proportions when making concrete on their own: eight buckets of crushed stone, three buckets of cement, four buckets of sand and two and a half buckets of water.
Next, the boards are laid along the lower shelves of the beams, a layer of roofing material is laid dry on top of the boards, after which a grid of rebar of a periodic profile is laid out along and across the beams, the diameter of which is at least 1 cm.
The dimensions of the mesh cell are 20x20 cm. The intersections of the mesh rods are tied with knitting wire or welded to prevent displacement of the reinforcement during concrete placement.
To completely cover the mesh with concrete, small pieces of rubble are placed under it, leaving a gap of at least four centimeters between it and the roofing material layer.
Concrete is laid in the form of strips between the beams, the thickness of the layer should be at least 15 centimeters. At the same time, the laying time should be calculated in such a way that it is necessary to have time to finish the strip and not leave it for another day, i.e. do not concrete strips in parts.
The most effective in terms of quality is the filling of the entire roof surface in one day. After pouring, concrete should be tamped, for this it is advisable to use a vibrator, or use a manual rammer.
When compacting concrete, care must be taken not to damage or move the reinforcement mesh.
Next, cover the concrete with a film of polyethylene (especially in hot weather) for at least three days, which avoids too rapid evaporation of liquid from it and, as a result, cracking of the upper layer of hardened concrete.
After waiting for the concrete surface to dry completely, slopes are made according to the procedure described above with the help of a heater, after which a screed is made and a rolled carpet is glued.
Flat roof self-insulation
One of the important differences between a flat roof and a pitched roof is the possibility of insulating it not only from the inside, but also from the outside during the operation of the house.
It is recommended to carry out external insulation first, and in case it proves to be insufficient in winter, to carry out internal roof insulation as well.
In the recent past, the most common way to insulate flat roofs was with the help of rigid thermal insulation boards, but at the same time, the load on the roof increases dramatically, so this method is practically not used today.
Insulation from basalt mineral wool is gaining more and more popularity, which not only has a much lower weight, but also provides better thermal conductivity and waterproofing.
In addition, it is not subject to mechanical stress and does not ignite, which is why it was so often steel from the very beginning. lay in the projects of one-story houses with a shed roof.
For the internal insulation of a flat roof, it is easiest to use 25-30 mm thick refractory boards made of expanded polystyrene as a ceiling insulation.
The installation of the plates is carried out as follows: wooden planks are attached to the roof ceiling every 40 centimeters, on which expanded polystyrene plates are glued using mastic or special glue.
Important: before proceeding with the insulation of the roof ceiling with polystyrene foam plates, the existing lighting fixtures should be dismantled.
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