Use the entire possible area, give the house originality and significantly reduce heat loss through the roof – these are the tasks that the attic solves. If there is a certain margin of safety at the foundation, in this way it is possible to turn a one-story house into a two-level one. It is also attractive that a do-it-yourself mansard roof can be built even without special building skills. It is important not to make a mistake with the choice of materials and do everything according to the rules.
Windows in the usual floor are located in the walls. There are no or almost no walls in the attics. Roofing replaces them. That is why windows are made special: they not only have to let in enough light, but also withstand wind and snow loads, which are much greater on roofs than on walls.
Skylights
When planning an attic, it is worth considering the recommendations of SNiP. They recommend that the window area be at least 10% of the floor area. So if the attic is divided into several rooms, each should have a window.
Of all the methods shown in the photo for arranging skylights with an attic, the inclined installation is the easiest to implement. At the same time, it is necessary to ensure the proper degree of waterproofing of the junction, as well as to use special models with a reinforced frame and reinforced glass – the load on the surface can be significant.
Inclined roof window
Benefits of a sloped roof window:
- more light, not so sharp borders of light and shadow;
- the roof surface remains flat, its relief is not complicated;
- relatively easy installation.
When planning such a window, it must be remembered that its area increases with an increase in the angle of inclination. At what height is it more convenient to install such a window and how its height in centimeters increases depending on the slope, see the photo.
The width of the window frame should be 4-6 cm less than the pitch between the rafters. Then it can be easily installed without disturbing the structure of the frame. If the window is wider, it is necessary to make a reinforced beam above it, calculate the load.
If you need to have a larger window, it is easier to put two narrow ones side by side. They look no worse than one big one, and there will be fewer problems.
Domer window protruding above the roof plane
When installing a dormer window, the geometry of the roof becomes more complicated: a valley appears on top and on the sides. Because of this, the truss system becomes more complex in both planning and assembly. The complexity of laying roofing also increases. All valleys are the places where leaks are most likely to occur. That is why it is necessary to do everything very carefully. In regions with a lot of snow, it is advisable to install snow retainers above such windows: so that they are not blown away during a sharp descent.
The advantage of such a window: near it you can stand in full growth. But they let in less light, the terrain becomes more difficult and the roof becomes more problematic.
Recessed attic window
A recessed window is usually used if an exit to a balcony is made through it. In other cases, this method of device is not the best option. That’s why:
- little light enters;
- the shadows are very deep, which is tiring for the eyes;
- the area of the room decreases.
Recently fashionable combination of two types of windows. Including vertical recessed
The geometry of the roof also becomes more complicated, although not to the same extent as in the previous version. In general, such windows are rarely made.
The simplest and most reliable roof window
The easiest way is to make a window in the end part of the attic. In this case, a reinforced frame or reinforced glass is not needed. Quite simply high-quality glasses are enough. It is this option that can most often be seen in country attics. This is the most inexpensive option, which is easily implemented by hand.
In fact, this is an ordinary window, just in an unusual place. The truss system is classical. For wide glazing, a reinforced beam is required on top.
Read more about gable roof construction here.
Rafter system
With the independent construction of private houses with an attic, usually a sloping roof is chosen. It allows you to get a large area. When compared to a duo.
The design of the sloping mansard roof is such that the overhangs can be lowered quite low, giving the house an interesting look. But the long overhang of the roof is not only a decorative role. They also cover the upper part of the wall from precipitation and divert the bulk of the water away from the foundation. Although when planning, you need to keep in mind that in strong winds they increase the windage. Because of this, it is necessary to use more powerful boards and beams. Therefore, the size of the roof overhang is chosen based on several considerations, the main of which is weather conditions.
Tilt angle
The choice of the angle of inclination of the roof depends on the roofing material. But you can change your mind about the material. What cannot be changed is the region and weather conditions. So they are decisive in choosing the angle of inclination of the attic roof.
The classic version is shown in the figure. The lower slopes in relation to the attic floor plane are inclined by 60 °, the upper slopes by 30 °. Based on these data and the parameters of your building, all lengths can be calculated. Just keep in mind that according to SNiP, the ceiling height in the attic cannot be less than 2 m. Then, by definition, this is an attic. A person will feel comfortable if the ceiling is raised to a height of at least 2,5 m. Based on this, according to the rules of geometry, calculate the required lengths.
In the classic version, the load from precipitation on the side surfaces may not be taken into account. Precipitation can only be held on the upper part, the angle of inclination of which is less than 45 °.
In general, the slope of the side surfaces usually ranges between 45° and up to 80°. The steeper the slope, the more windage it has. This must be taken into account. And in regions with strong winds, it is better to make more gentle roofs. Then the wind loads will be perceived much better.
Types of rafter systems of broken roofs
For the manufacture of a sloping roof frame with their own hands, pine lumber is most often used, the grade is not lower than 2. The choice of the section of timber and boards depends on the size of the roof, the selected roofing (its weight), wind and snow load in the region, the installation step of the rafters. All these parameters are taken into account in the calculation. The technique is prescribed in SNiP 2.08.01-89 and TCP 45-5.05-146-2009.
With rafters
Below in the figure is a drawing of a frame with hanging rafters. It can only be implemented if the base of the upper triangle is no more than 4,5 meters (in this case, this is the width of the attic room). If more, you will have to make layered rafters, which should rest on the load-bearing wall in the middle (the attic will turn out to be divided into two parts by a row of beams).
Another version of the upper part is shown in the photo below (the picture is clickable). In this case, the side rafters are reinforced with struts. They significantly increase the rigidity of the system.
There is a second way to achieve a similar effect – to set contractions – in the figure they are only outlined with barely visible lines. The length of the side rafter leg is divided into three, contractions are set in these places. They will be needed if the roofing will have a solid weight.
For a small building, the roof frame can be generally simple: at the top there are two hanging rafter legs, a puff, floor beams, racks and side rafters (pictured below).
Rafter installation step
The mansard sloping roof of a small house (width no more than 6-7 meters) has been built so many times that, based on experience, we can say what materials should be used. Many parameters are dependent on other materials. For example, the installation step of the rafters is tied to the parameters of the insulation.
To ensure that there is as little waste as possible during insulation, installation is easier, it is necessary that the distance from one rack to another is slightly less than the width of the insulation (by 20-30 mm). So, if you are going to use mineral wool, its width is 60 cm. Then the racks must be installed so that the clearance between two adjacent ones is 57-58 cm and no more.
Dimensions of the board for the truss system
The width of the board for the rafter leg is again determined based on the insulation. For the central zone of Russia, the required thickness of basalt wool is 200-250 mm. That’s not all. In order for the thermal insulation to dry out, a ventilation gap of 20-30 mm is required (without it, the condensate will gradually rot the wood and render the mineral wool unusable). In total, it turns out that at a minimum the width of the rafter leg should be 230 mm. The thickness of the board is at least 50 mm. This is in regions with mild winds and not very heavy snowfalls. Summing up, for all rafters – ridge and side – a board of 230 * 50 mm is required.
If lumber with such characteristics turns out to be too expensive, it will be possible to make insulation in two directions: part along the rafters, part, stuffing the crate, across. You can lay a minimum of 100 mm of basalt wool, therefore, you can take a standard board 50 * 150 mm and leave it on the ventilation gap of 50 mm, or order a non-standard 130 * 50 mm. See what is more profitable in terms of money.
For racks and beams, it is better to take a beam of at least 80 * 80 mm, better – 100 * 100 mm. Especially in areas with difficult weather conditions – with heavy snowfalls or strong winds.
For a more accurate estimate, ask the experts. This is a long process, consisting of the collection of loads from the roofing material, the structural elements themselves, wind and snow loads. After that, according to a certain formula, the elements are selected.
Features of mansard-type roof insulation are described here.
Do-it-yourself mansard roof: installation procedure
The Mauerlat device on mansard roofs is no different from the standard version. If the house is made of timber or logs, you can use the top crown as a Mauerlat. It is only pre-treated with impregnation with high protective properties.
If the wall is made of foam blocks, a reinforced monolithic belt is arranged on top of it. On a brick wall or made of shell rock, other similar materials, the device of such a belt is optional. Waterproofing is laid on the wall in two layers, and on top – a timber treated with an antiseptic – 150 * 150 mm or a log. It is fixed with embedded studs.
When assembling all elements, long nails are used – at least 150 mm long. In the most critical places, it is better to connect three or more elements with bolts or studs with double-sided threads. It is desirable to strengthen all joints with steel plates or corners.
You can read about building a house from aerated concrete in this article.
The first method
The installation of mansard roof rafters is done in two ways. First: parts are assembled on the ground, then they are lifted up in finished form. There, the first to expose the extreme structures that will become the gables. They are placed vertically, fixed. It is often more convenient to fix them with long bars nailed to the wall (temporary). The following assembled structures are inserted into the prepared recesses in the Mauerlat (they are made with the required step). They are set strictly vertically, carefully fixed. If necessary, install additional temporary spacers that fix them in the desired position. Side rails are installed.
How to build a sloping roof in this way, collect nodes, see the video below.
second method
The second method – the construction of a sloping roof is carried out by sequentially collecting elements right on the spot. This method is more convenient if the structure is large and when assembled it can only be lifted using special equipment (crane).
First, floor beams are laid. Racks and puffs are attached to them, temporary struts are placed to hold them in the vertical direction. Next, the rafters of the upper and side legs are assembled, puffs and jibs are installed.
During installation, the following sequence of actions is observed: first, the extreme elements are installed and set in the desired position, securely fixed. If necessary, use temporary spacers. Between them, a fishing line, rope, lace is stretched, which will serve as a guide for the installation of all subsequent elements. This simple move allows you to get the perfect geometry (do not forget to check the slope angle, verticality or horizontality).
Puffs are attached over the racks – bars, to which the side rafters are then fixed and on which the puff of the upper triangle is installed. Puffs are attached with metal corners. Since the beams are long, they sag. This is further eliminated – after the installation of the upper rafter legs – using vertical beams of a fixed or adjustable height. And temporarily they can be propped up with racks (so as not to pull the entire system).
To make it easier to maintain the desired angle when installing the side rafter legs, templates are made according to which the cuts are made. But since the geometry of DIY buildings is rarely perfect, adjustments may be needed. To check the resulting angle of inclination from several boards, another template is knocked down, which checks the correct installation.
If the standard length of lumber – 6 meters – is not enough, either order the required length (expensive) or increase it. When building up, two boards with a size of at least 0,6 meters (30 cm on each side of the junction) are nailed to the junction. They are nailed on both sides or bolts are used.
After installing the side rafters, it remains to install the top ones. A template is also made for them, it is first sawn on the ground, and installed at the top.
The top part can be done in different ways. Its structure depends on the width of the base. See the photo below for how to make it.
Since the device of the mansard sloping roof does not provide for the presence of a ridge, a beam is stuffed in the middle, to which the slopes are attached, fixing the triangle in the required position.
Ga this can be considered that the mansard roof is assembled with your own hands. It remains to mount the roofing material and do the insulation (you can do it in that order, you can do it at the same time). Features of mansard roof insulation are described here.
Nodes and their drawings
When installing the truss system, questions may arise regarding the assembly of nodes – the intersection and connection of several structural elements. In the photo you see drawings of key connections.
The second option is to connect the side rafters and the upper triangle. Bolts are used for more secure fastening.
The methods for attaching the rafter legs to the Mauerlat or, as in this case, to the side beam are shown in the figure below. To make it easier to mount a heavy element, a stop board (bar) is nailed to the rafter from below, which limits its movement: the board rests against the edge and prevents it from falling lower.