The roof of any building has one main function, and this is the protection of the house from rain. This is her main purpose, except that she gives the building a certain style. Based on this, all calculations of this important structure are made. Of all the existing structures of modern layouts, the most in demand are two-pitched and multi-pitched structures, if an attic house of a complex system is being built. In any case, the roof project is done according to typical rules, the main of which are determining the load on the house and the load on the frame of the rafters. The width, height, and angle of inclination of the slopes will depend on this.
Varieties of roofs
According to their use, there are attic and unreachable houses. And by design there are two types. It is pitched and flat. But let's talk about everything in order. In modern construction, it is very rarely asked how to make a flat roof. Today it is irrelevant, as flat roofs are rarely used. The only drawback of the flat design is the small tilt angle to drain rainwater. They leak very often and require constant maintenance and repair. Many houses with flat systems are converted to pitched, which have many advantages. These designs are easy to operate and do not require frequent repairs. Their very great variety. This is a single-pitched, and gable, and hip, and half-hip, tent and multi-gable, broken, conical and domed roofs. There are also combined ones in this list, in which several types are combined.
To have at least some idea of the types of roofs, you need to give a brief description of each:
- The name "gable" itself gives a reasonable explanation that in this design there are only two pitched areas.
- The hip and semi-hip roofs, which already have four slopes, are more complex in design. This configuration is used in the construction of attic rooms. The difference between the two is that the former have lateral slopes in the form of triangles over the entire width, while half-hip ones have only small pitched triangles that cover the pediment walls.
- A single-pitched roof in housebuilding is used only in small structures: it is relevant for garages, small country houses and other small structures.
- And the roof list continues in the form of a tent with four slopes that converge at one point in the ridge.
- And finally, broken pitched ones have a complex structure. Only it, as it were, consists of two planes with one angle of inclination, and the other two with the other. The lower slopes are a continuation of the two upper. They are connected at the level of the attic floor. The lower slope continues the upper, but only from a different angle.
Roof project
First of all, you need to pay attention to climatic conditions and the loads that will act on the rafter system, on the box of the house and on the foundation. Typically, design documentation is produced by design firms. How to make a roof in this case? The builder’s task is only to convey to the designer his desires in the choice of configuration and provide him with geodetic, geological and climatic studies of the area on which the building will stand. The project gives the exact dimensions and design plan. All loads are determined and recommendations are given in the choice of materials for the house, and for the roof, and for roof insulation.
Also, projects indicate all nodal connections and fastenings in the rafter frame. All its dimensions and installation locations of the transverse and longitudinal beams are indicated here. But, as usual, experienced craftsmen do not always turn to project documentation and do everything with their own thoughts and experience. Therefore, to test the experience of the masters, they need to show the project documentation for reading it. Not all masters can read projects. That's about how developers need to act on all issues of how to make a roof, so as not to fall into the trap of inexperienced craftsmen, so that later you do not have to repair your house.
Configuration and dimensions
Roofing material is important, much depends on its weight and resistance to the elements, wind, frost, precipitation. The first parameter is the width, which is determined only by the dimensions of the house. This is determined by the architectural plan. And further parameters will be directly related to the width and climatic conditions.
The height and slope of the slopes - these indicators are interrelated and related to climatic conditions. If the house is being built in areas with high rainfall, then, accordingly, the question of how to make a roof with the desired slope and height will be in first place to provide the most effective protection against rain and snow. From the width and steepness, the height is calculated.
It is clear that it is important to observe the proportions between the height, width and slope of the slopes. From the slope and height, roofing material is selected, which is selected not only for the configuration, but, first of all, in relation to climatic conditions: precipitation, wind, frost and snow. After all, the lion's share of the loads of these elements falls on the roofing material. Weight and resistance, and flexibility, and resistance to temperature changes play a role in his choice. This also applies to the wooden roof.
System
The second step in determining the configuration will be the choice of the type of frame. For a gable structure, there are two types: layered and hanging. The difference is small, but it is of great importance in calculating the loads on the house and on the rafter system itself. Take the first construction first. This method involves a more reliable fastening of the rafters. With such a system, the rafters rest on the longitudinal beams, the first of which lies on the strapping base, on the Mauerlat. The rafter's foot rests on it and is connected by several fasteners. In the middle of the frame system , lateral runs are installed, to which the rafters lean. From this, the system is called overtone. The third beam is a ridge, on which the rafters lie with their ends. At all docking nodes, they are fastened with metal mounts, angles, screws or nails.
Hanging construction
In this frame there is no sub-beam beam structure. The rafters with their paw are mounted on the Mauerlat, and the ends are connected in the ridge part. It seems that they hang above the box at home, leaning on the beam only with their paws. Such a rafter system has a large tensile load on the rafter triangle. To fix it, fastening the rafter legs with transverse beams, props and slopes is used. Such a system is used for small houses. This is not to say that it is less effective. Each configuration has its advantages and disadvantages. To strengthen the fastening of the hanging rafter structure, transverse beams are used to connect the rafter legs at the base.
The width of the roof. Payment
In the eaves, the size is determined by summing the width of the box of the house and two eaves overhangs. Eaves overhangs can have different sizes:
- So, for a metal tile, eaves overhangs are made within 40-50 cm.
- For slate, the eaves overhang is 10 cm.
- Bituminous tile - 30-40 cm.
- Decking - 50 cm.
- Ceramic tile - 50-60 cm.
If, for example, the width of the box becomes 4 m, then, accordingly, the width in the cornice will be up to five meters when using a metal tile, the eaves of which are 40-50 cm. The calculation of the width in the cornice is done due to the need for more reliable protection of the walls of the house from oblique rains. Therefore, the increase in the cornice width occurs due to the elongation of the transverse logs of the strapping beam or brickwork.
Slope slope. How to make a calculation
The angle of inclination of a pitched roof, including a pitched roof, depends on three factors:
- The first is the roofing material and the weight of the roof, along with the roofing cake.
- The second effect on slope steepness is climatic conditions. In areas with abundant rain and snowfall, the degree of slope will increase.
- The third slope slope indicator is the total weight of the rafter system. And yet, the indicator depends on the number of joints of roofing sheets.
The more joints, the steeper the plane should be. The quality of the roofing material also has something to do with the slope. The harder the material, the greater the tolerance for lowering the degree of inclination. It has an effect on the steepness and weight of the material. The heavier the roofing sheets, the greater the steepness. The angle of inclination varies from 10 to 60 degrees.
The calculation of the angle of the roof, that is, the slope of the ramp, is carried out for such a formula:
- Tg (A) = h / c;
- Tg (A) is the tangent of the angle;
- h - half the length of the span of the house;
- c is the height of the rafter system, that is, the roof from the base to the ridge.
Take the approximate dimensions. If the span of the house is 12 m, then its half is 6 m. The height of the rafter system is 3 m. We substitute these sizes into the formula and get:
Tg (A) = 3: 6 = 0.5.
We got the tangent of the angle 3/6 or 1/2 (or 0.5). We recall the geometry and from the table of tangents we calculate how many degrees the tangent of the angle 0.5 has. In our example, it becomes 27 degrees.
The height of the ridge. How to calculate
This parameter also has a certain dependence on the width, steepness and weight of the roofing system. The heavier the roof, the steeper the ramps should be. The slope of the slopes also affects the height. In fact, in fire safety measures, the top cannot be lower than 1.6 m. If the steepness is large, then the height will increase. In this case, in order to reduce the height while observing the steepness, a broken or cut design is made. In the ridge part, it can have a flat end. Accordingly, a broken rafter frame is also created for the broken system. In the upper part, the base of the sub-rafter system is built, on which the rafter legs rest . It is necessary to make a layered frame. The calculated height of the ridge is calculated by the formula:
- H = L x A.
- H is the height of the ridge.
- L is a leg of a triangular truss.
- A is the tangent of the triangle of the farm.
Take, for example, the width of the house is 6 m. Divide the width of the house by 2 and get a leg of a triangular farm. In our example, the leg is L = 3. From the tables we write out the tangent of 40 degrees - 0.84.
We substitute the numbers in the formula and get the height of the ridge. H = L x A = 3 x 0.84 = 2.52 m. The height of the roof ridge is 2.52 meters.
Roof truss
Reliability is the strongest guarantee of the durability of any building. Therefore, the design and installation of all roof units must be given the same special attention as all the other main parts of the house - its foundation, load-bearing walls and ceilings.
All structures use typical principles and rules, according to which the rafter system of the building is built, and all nodes of the roof device are strengthened. The frame is installed on the basis of the upper crown, called Mauerlat, which can be made of wooden beams, concrete or brick bases. If wooden is used, the beams are mounted on bolts or threaded rods embedded in the upper part of the wall.
Logs are drilled for each reinforcing bolt, and a beam is mounted on them around the perimeter. In addition to the bolted connection, the longitudinal beams are reinforced with transverse mortise locks paws, which are cut on the lower and upper beam. There are several designs of the rafter frame. And in how to make the roof more economical and efficient, you need to know which system is most suitable in certain conditions.
To cover large spans, hanging rafters are used, which are strengthened with the help of sliding supports. In addition to them, in the hanging structure, the upper transverse beam is used, which is installed closer to the ridge. The design of the layered frame is created from rafters, which are fixed by several fasteners. These are vertical supports, and slopes, and nodal joints.
How to choose materials
Materials for the home, including for roof insulation, need to be selected based on their qualitative indicators regarding elasticity, temperature differences and resistance to destruction under the influence of external factors. The modern construction industry has in its arsenal many types of roofs that have high quality indicators.
The start of building your own home puts the developer in a difficult choice of material. There are no exact rules here. But there are still some tips in choosing roofing material. The first thing you should pay attention to the cost and configuration of the elements of the roof. Each type has a number of components for installation. The second rule in choosing a coating is that the material is suitable for the configuration of the building, roof structure, steepness and type. For example, for roofs with a low slope, a more rigid material, a metal tile, is required.
The choice of roofing material is also associated with climatic conditions. In areas with abundant rainfall, it is advisable to choose for quality and strength. But for a flat system, it is better to use durable polyvinyl chloride membranes.
Roof Mounting
To prepare the installation of roofing material and insulation, flooring of the rafter frame is made. Under hard flooring is installed from wooden battens with a cross section of at least 40 mm.
For a soft coating of any configuration, including a pitched roof, you need a solid flooring made of wooden boards or plywood. In both cases, the flooring creates additional reinforcement of the rafter frame and a flat surface for installing sheets. The next installation process is the installation of waterproofing film, which is made on wooden flooring. To create a ventilation gap between the roof layer, an additional crate is installed on the waterproofing film with a wooden plank with a cross-section of no more than 10 mm.
The coating layer is installed on an additional crate according to general rules, depending on the material used. After the flooring, insulation is made, which is installed from the attic. The insulation layer is covered with a vapor-tight film and covered with a facing material. Thus, the roof of the roof consists of several layers that create reliable hydro and thermal insulation.