Roofing: what you need to know

When faced with the construction of a private house, in the process of designing a structure, the closest attention is paid to the shape of the roof, since the general appearance of the entire building depends on it. In the framework of this article, we will analyze the roof structure, what are the forms of floors, materials and what is better to choose.

The roof is always a compromise between the beauty and financial capabilities of the building owner. Of all the variety of types of roofs, absolutely flat and single-pitched roofs are quite rare, mainly double-pitched and combined options with different angles of inclination of the roof elements.

A pitched roof can be residential or attic, i.e. either a living space with full windows and quite spacious is created under the structure, or an attic is simply arranged according to a simplified scheme.

Consider the structural elements of the roof using the example of a simple attic roof.

The roof consists of a frame and a roof. The frame, in turn, consists of (see figure below)

1. Mauerlat. It serves as a support for the rafters, is a beam or a log hewn from below. If the walls are made of lightweight materials (foam, aerated concrete), then the mauerlat should have a continuous shape. If the walls are monolithic (brick, concrete), then under each rafter support it is allowed to put a Mauerlat with a length of at least 50 cm.

   

2. Rafter. This is the main load-bearing element of the roof frame, so the material for the rafters is chosen of high quality, without flaws, with a humidity level of not more than 22%. The material can be thick boards and beams, the section depends on the size of the roof, its weight, span width, slope angle and design load. If the width of the roof is significant, then to help the rafters are used:

• Puff.
• Rack.
• Strut.

These structural elements increase the rigidity of the structure and prevent the rafters from “moving apart”.

3. Crate. This element is specially designed for fastening the roof. Depending on the material and the angle of the roof slope, the step of the crate is chosen.

Rafters, in turn, are divided into layered and hanging. Laminated rafters additionally perform the role of floor elements, only they are not located exactly, but at a certain angle.

Such rafters rest with their ends on the walls of the house, and with the middle part on the internal supports, if any. The figure below shows a simple version of the device for layered rafters, where 1 is a rafter, 2 is a crossbar, 3 is an overlap.

Such rafters are used for small, up to 6 meters, spans between supports.

Hanging rafters rest purely on the walls of the house, using various additional elements to strengthen the rigidity of the structure (see the figure below).

1-mauerlat, 2-rafter, 3-puff, 4-headstock, brace. Such rafters exert only a vertical load on the Mauerlat. Often used in buildings without internal supports, as well as in combination with light walls.

Rafter legs in this case are always combined with puffs. This design is always very rigid, since only the outer walls are the supports.

Place of rafter support

It is very important for the roof to properly and reliably fasten the rafter leg against the wall of the house. In houses with different walls, different support structures are used.

1. In houses made of wooden beams or logs, the rafters rest on the upper elements, made with spikes to fix the support.

   

2. In frame buildings, the support rests on the upper strapping strip of the frame.

3. For a brick house, other stone buildings use Mauerlat. A beam for him is chosen 140-160 mm thick.

Tip: the places where wood and brick (concrete, etc.) touch are necessarily laid with waterproofing material, otherwise the condensate will constantly wet the wooden parts.

It is very important that at the place of support the rafter leg does not slip along the puff. To do this, use such elements in the design as teeth and spikes on the rafters, and stops on stretch marks.

In the case of a large load on the connecting elements of the structure, it is advisable to use a double tooth.

For the purpose of a tighter connection, fixing with bolts (3, 4) is often used.

Attention! The use of bolts weakens the section of wooden elements, these are weak points in the future.

At the top point, the rafters are attached to the ridge, which is rather complicated in design. The figure below shows a simple ridge (top), where the rafters are simply held together with a scarf (8), and a complex ridge knot.

Let's dwell on it in a little more detail. The rafter legs (1) are attached to the rack (2) with the help of cut out elements (tooth and saddle), in addition, they are also fixed with metal ties (7) for reliability. The brace (3) serves as an additional support. The tightening (4) takes on part of the load, and the stand (2) is fixed to it with bolts (6).

Attention! The roof must protect the walls of the house from atmospheric and weather influences, so its extension outside the walls must be at least 50 cm.

crate

The frame is almost ready, it remains only to install the crate for attaching roofing material to it. The step of the crate is selected based on the characteristics of the coating. To do this, a beam is taken and tightly fixed to the rafters, and the joints of the beams should go apart in different lanes.

In the case of using a soft roof, the crate is covered with a continuous flooring. To do this, take moisture-resistant plywood or OSB board. Sometimes boards are laid in the old fashioned way with a gap between them of a maximum of 10 mm.

Insulation

If the roof device involves an under-roof space that is used for housing, then due to natural ventilation, moisture does not accumulate under the roof, but leaves with air currents.

If we are dealing with an attic, then there is a high risk of moisture accumulation in it, because. below the attic, the living space is warm, and the attic is not heated, which means that the temperature difference will give condensate.

The principle of roof insulation is the same: waterproofing is first laid under the roof, then a layer of insulation (about 50 mm) follows, then vapor barrier.

Vapor barrier can be laid directly on the attic floor, its task is to prevent evaporation from the living space into the attic space.

roofing material

Now that everything is ready to cover the roof with roofing material, let's look at their types.

The most popular material for pitched roofs today is galvanized metal in a wide variety of forms, a prime example, shed roof from standard corrugated board. This is a metal tile, and profiled sheets, and a seam coating.

Working with such material is easy and fast, the area of ​​the sheets is large, so the work goes smoothly. The cost is acceptable, the material is durable, non-flammable. Of the shortcomings, only poor sound insulation, and high consumption in scraps.

Asbestos-cement slate (or just slate). An excellent inexpensive material that has been used in the field for decades. True, more and more for non-residential technical premises, since it does not have a presentable appearance, and asbestos is an environmentally dirty material.

soft top. These are materials based on fibers impregnated with bitumen. This includes shingles, ondulin, various subspecies of roofing material. Easy to work with, material is flexible. Perfectly repeats any intricate roof configuration.

At the end of the article, we suggest watching a video about roofing.

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