Sheathing for corrugated board: material calculation and installation technology
In recent years, due to its beautiful appearance, high strength, low weight, reasonable price and ease of installation, corrugated board has become very popular among private developers. But at the same time, the installation of profiled sheets has its own nuances that it is desirable to know, especially when the construction of the roof is planned to be done independently. This is especially true of the lathing on which the covering material is attached, since the quality of the fasteners directly affects the rigidity of the coating and its service life.
Sheathing for corrugated board
The construction of a roof is a cycle of work on which not only the longevity of the entire building and the comfort of living in it depend, but also the safety of the inhabitants. Therefore, construction methods and technology are strictly regulated by regulatory documents, the key ones of which are SP 17.13330.2011 - an updated edition of the collection II-26–76 “Roofs” and SP 20.13330.2016 “Loads and Impacts” - an amended and edited version of the instructions 2.01.07– 85 *.
According to building codes, corrugated board can be installed on any roof shape. Nevertheless, for residential buildings, it is recommended to maintain a minimum slope of 12 °. On shallower structures (6-12 °), construction experts advise to mount a waterproof layer under the sheets, although when covering with corrugated board its presence is not required, or to seal the transverse and longitudinal joints of corrugated plates.
Building standards do not limit the configuration of roofs for corrugated board, but stipulate a minimum slope - from 12 °
The lathing is one of the elements of the roofing pie - the basis for the coating, which can be in the form of metal girders or wooden boards and bars laid with continuous flooring or with a certain pitch, due to the type of profile and the slope of the roof. When filling the lathing, the correct calculation of the cross-section of the materials, depending on the expected loads, respectively, SP 20.13330.2016, is of great importance.
The height and thickness of the profile, the slope and dimensions of the roof, as well as climatic influences affect the choice of material for the lathing - metal or wood
The lathing performs a number of important functions:
- prevents roof sagging;
- redistributes and evenly transfers loads to the rafters;
- ensures the strength of the roof structure;
- increases the bearing capacity of the roof, as well as its heat, sound and waterproofing properties.
But in addition to the key responsibilities, the crate, together with the end components, plays another significant role - a regulating one, so that small deviations in the geometry of the slopes that have arisen during the installation of the rafter system can be corrected. In this regard, after assembling the rafter frame, before laying the roofing pie, it is imperative to make a control measurement of the slopes along the diagonals. In case of discrepancies with the design values, mark off a figure with acceptable tolerances on the slopes and mark it with respect to it.
The regulating role of the crate makes it possible to correct deviations in the geometry of the slopes with the design values
Video: determining the geometry of the ramps
Structurally, the crate for profiled sheets is:
- single layer;
And according to the created surface:
- sparse (step by step).
Of the variety of lathing for corrugated board in individual construction, a single-layer sparse structure is most often used
Usually, a single-layer sparse lathing is used, which is more difficult to install, but does not make the structure heavier and makes it possible to save on materials. A solid crate (with gaps of 1–2 cm) is stuffed under a profile with a low corrugation, around dormers, ventilation and chimney pipes, fire hatches and in other places where additional rigidity of the base is required.
A two-layer lathing consists of load-bearing beams stuffed to the rafter legs parallel to the ridge ridge (bottom layer) and an upper layer of planks, OSB boards, plywood, edged or grooved boards, laid perpendicularly or at an angle of 45 ° relative to the first layer and attached to it. Usually, this type of lathing is assembled in order to save lumber when arranging a roof structure with a large rafter pitch, or when it is necessary to align errors in the construction of a rafter frame.
With a lot of pressure on the roof, they equip a double combined lathing, where the metal structure acts as the bottom layer, and wood, plywood or particle boards are the top layer, which allows you to create a solid base for corrugated boarding.
The combined construction of metal and wood creates a solid base that can withstand heavy loads
The choice of lathing depends on the thickness of the metal profile, wave height, roof shape, roof slope and the quality of coating processing. Therefore, in addition to regulatory documents, it is important when choosing to be guided by the instructions of the manufacturers of profiled sheets, which indicate special requirements for the installation of products.
Video: mansard roof - insulation and installation of the crate
The load-bearing capacity of the lathing determines the material from which it will be made - wood or metal. Metal sheathing is usually used on large roofs with a low slope or in climatic regions where extremely heavy loads act on the roof. Runs are made according to collection 31-10-97 from a channel, a pipe of square, round or oval cross-section, a corner and other moldings.
The metal base for the corrugated board has a high bearing capacity with a relatively low weight
Metal crate has undeniable advantages, including:
- high level of fire safety and non-susceptibility to decay;
- maximum openness;
- flawless smoothness, which has a positive effect on the strength of the roof covering.
But, despite this, in private low-rise construction, preference is traditionally given to wood, usually using coniferous sawn timber - beams or bars, edged and unedged boards. An edged board with a section of 32x100 mm is considered to be universal, and therefore more often than others used, - it is durable, of high quality and at an acceptable cost. Cheaper boards 22x100 or 25x100 mm, unfortunately, are not strong enough, which is why they are used for the construction of simple lightweight structures with a rafter pitch of up to 600 mm. Beams 25x50, 32x50, 50x50 mm, etc. are used in the construction of complex configurations with many decorative fragments. Due to its hardness, it will protect the roof from deflection and deformation due to increased loads on the slopes.
For stuffing the lathing under the corrugated board, a bar is best suited, as well as an edged and unedged board
Less often they work with grooved - for a solid base - and calibrated - for a sparse structure - boards. They are, undoubtedly, beautiful, well-processed, with clearly consistent dimensions, as a result of which there is practically no waste during sorting, but very expensive. Such boards are mainly used to cover the floors of a house under construction.
Despite the high quality of processing, grooved and calibrated boards are rarely used for lathing due to their high cost
It is more familiar to work with wood, it is easier, moreover, it is cheaper than metal, and with the right selection and appropriate grinding, the wooden crate can serve no less than the entire structure.
For continuous flooring, plywood, OSB-3, OSB-4 and other moisture-resistant sheet materials are used. The frame is, of course, assembled very quickly, but in terms of 1 m² the price of a board turns out to be almost half that of particle boards and three times less than moisture-resistant plywood. Therefore, it makes sense to also use wood for a solid crate - it is more reliable, profitable and of better quality.
Edged or tongue-and-groove boards as well as particle boards or plywood are laid quickly, with a minimum of seams, and create a perfectly flat continuous base
How to ensure the bearing capacity of the lathing and choose the correct section of sawn timber or rolled metal, we will consider a specific example. We are building a house, for example, in Vologda. The mansard roof is covered with C-21 corrugated board with a thickness of 0.5 mm. Pine lathing, rafter pitch 1.0 m, roof slope 35 °. We will preliminarily accept the cross-section of the timber for the lathing 25x50 mm (b - width 50, h - thickness 25) and an installation step of 300 mm (0.3 m).
Table: the optimal step of wooden lathing for corrugated board
|Corrugated board brand||Roof slope, deg.||Sheet thickness, mm||Lathing step, mm|
|S-8||not less than 15 °||0,5||solid|
|S-10||up to 15 °||0,5||solid|
|more than 15 °||0,5||up to 300|
|S-20||up to 15 °||0,5; 0,7||solid|
|more than 15 °||0,5; 0,7||up to 500|
|S-21||up to 15 °||0,5; 0,7||up to 300|
|more than 15 °||0,5; 0,7||up to 650|
|NS-35||up to 15 °||0,5; 0,7||up to 500|
|more than 15 °||0,5; 0,7||up to 1000|
|N-60||not less than 8 °||0,7; 0,8; 0,9||up to 3000|
|N-75||not less than 8 °||0,7; 0,8; 0,9||up to 4000|
|Note: in regions with strong, frequent winds, it is necessary to reduce the pitch of the crate up to halving.|
- We are looking for trigonometric values of the angle of inclination according to the Bradis table → sin 35 ° = 0.574; cos 35 ° = 0.819.
- We determine the snow load by calculating the value of µ, as well as using the data of the map of the weight of the snow cover by region → S = µ x Sg → 0.033 x (60 - 35) x 224 kg / m² = 184.8 kg / m². Note: according to SNiP 2.01.07-85 *
- if the angle of inclination is α ≤ 30 °, then µ is taken as 1;
- when α ≥ 60 °, then µ = 0;
- at 30 ° <α <60 µ is calculated by the formula 0.033 x (60 - α).
The snow load on the crate is calculated based on the standard values, as well as the weight of the snow cover for a particular region.
- We determine the snow load by calculating the value of µ, as well as using the data of the map of the weight of the snow cover by region → S = µ x Sg → 0.033 x (60 - 35) x 224 kg / m² = 184.8 kg / m². Note: according to SNiP 2.01.07-85 *
- The wind load is not taken into account when calculating the strength of the lathing according to SNiP 2–25–80.
- The weight of the C-21 corrugated board is 5.4 kg / m² and the own weight of the selected crate → (0.05 x 0.025 x 5000): 0.3 = 20.8 kg / m², where 5000 is the density of pine in terms of per running meter ...
- The overall result is presented in the form of a table.
Table: collecting loads on the crate
|Type of loads||qn, kg / m²||yf||q, kg / m²|
|Roof from corrugated board||5,4||1,1||5,9|
|Net weight of the crate||20,8||1,1||22,9|
After filling in the table, we continue the calculation. Sheathing boards should cover a maximum of 2 spans, that is, 5 rafter legs. Let's check the strength of the selected boards, which will be stuffed between two rafters, since the calculation of the spans is much more complicated, and the result will be approximately the same:
- With the chosen lathing pitch of 0.3 m and an inclination angle of 35 °, the standard load on the boards is → qn = total load x lathing pitch x cos 35 ° = 287.5 x 0.3 x 0.819 = 70.638 kg / m, and the calculated load qr = total load x batten pitch x sin 35 ° = 287.5 x 0.3 0.574 = 49.508 kg / m.
- Then the value of the transverse bending moment for calculating the strength Mz = 70.638 x 0.95²: 8 = 7.969 kg / m = 796.9 kg / cm, and longitudinal, that is, the bending of the board relative to the y axis → My = 49.508 x 0.95²: 8 = 5.585 kg / m = 558.5 kg / cm. Where 0.95 is the coefficient of reliability, regulated in the collection 20.13330.2016; indicator 8 - the number of lathing boards per one rafter leg - we have adopted conditionally, but calculated by the formula → the length of one rafter is divided by the total value of the width of the board / timber for the lathing and the selected step.
- The cross-sectional resistance of the lathing will be → Wz = bh²: 6 = 5 x 2.5²: 6 = 5.208 cm³ and longitudinal section Wy = hb²: 6 = 10.417 cm³, where b is the width of the bar, h is the thickness of the bar. Note: we used formulas according to SP 64.13330.2011 for simple geometric shapes, in our case for a rectangle, since a 25x50 bar has a rectangular section.
To calculate the resistance of the section of a bar 25x50 mm, we use the formulas for a rectangular figure
- We check whether the strength conditions of the selected bar are met according to the loads according to the formula → Mz : Wz + My : Wy ≤ R, where R is the standard resistance indicator for wood of I grade = 140 kg / cm², II grade 130 kg / cm², III grade 85 kg / cm² according to SP 64.13330.2011 tab. 3 → 796.9: 5.208 + 558.5: 10.417 = 153.01 + 53.61 = 206.62 kg / cm², which is more R even for grade I wood. That is, the selected section of the timber is small, the crate from it will not withstand the expected loads. In this case, you need to increase the cross section and re-calculate, which we will do.
- We increase the cross-section of the timber from 25x50 to 50x50 mm. Q valuesn, qr, Mz and My remain the same, we calculate only Wz and Wy, which will be equal to each other, since the 50x50 mm beam has a square section. So Wz and Wy = thickness or width of the timber in the cube: 6 = 5³: 6 = 20.833 cm³.
- Checking → 796.9: 20.833 + 558.5: 20.833 = 38.25 + 26.81 = 65.06 kg / cm² ≤ 85 kg / cm² for grade III wood.
- Considering that wood is still an expensive pleasure, we will calculate an intermediate option - using a bar with a section of 32x50 mm. We have Mz = 796.9 kg / cm and My = 558.5 kg / cm, Wz for rectangular section = 5 x 3.2²: 6 = 8.533 cm³ and Wy = 3.2 x 5²: 6 = 13.333 cm³. Then → 796.9: 8.533 + 558.5: 13.333 = 135.28 kg / cm² ≤ 140 kg / cm², that is, in this case, you will have to use only grade I wood, for which the value of R = 140 kg / cm².
- We conclude: for our example, a timber of 50x50 mm I, II and III grades or 32X50 mm only of I grade is suitable. Which is more profitable to buy, the developer himself decides based on his capabilities.
We examined the principle of calculating the strength of the lathing according to the selected section. This is a complex, but necessary calculation in order to immediately select the most durable material for the batten, capable of withstanding the influences exerted on it.
In addition, it is advisable to make additional calculations for the deflection of lumber, using SNiP 2–25–80 "Wooden structures" p. 6 "Beams, decks, purlins". Although the standard 2.01.07–85, the deflection of attic structures is unlimited, therefore, when arranging cold attics with a short stay of people there, it makes no sense to carry out additional calculations, especially since they require engineering knowledge.
But you can check the boards for deflection during the construction of warm mansard roofs using the old "old-fashioned" method, which has not let anyone down yet - nail a board between two rafters and stand on it. If there is no deflection, then the section is selected correctly. The only condition is that a person of average build, who is not afraid of open spaces and heights, should participate in the experiment.
Wooden structures, as well as metal ones, must be well ventilated, sufficiently open and accessible in all parts of the building for inspection, repair and periodic protective treatment.
Open access to the crate will provide an opportunity for repair and protective treatment
A well-calculated cross-section of lumber will help to avoid many problems, such as:
- weakened fastening of the covering material, which will inevitably lead to leaks;
- accumulation of condensation due to poor ventilation of the under-roof space and, as a result, rotting of the insulation and damage to all parts of the structure;
- difficulty or impossibility of installing additional and shaped elements.
In this regard, it is not worth thoughtlessly to save on materials for the rafter system and lathing. However, it is still possible to reduce the cost of constructing the supporting and enclosing system if:
- purchase materials during the off-season, when suppliers offer good discounts;
- purchase the necessary materials for the roof in bulk;
- take wood of a lower grade, and then subject it to careful sorting and further processing - pruning, knotting and grinding;
- to harvest wood by yourself, having issued permits in local self-government bodies and forestry;
- along with standard sizes, choose short molded products, which are much cheaper;
- make the purchase of materials directly from manufacturers, and not through intermediaries, which will make it possible to profit from the cost and minimize defective products.
Video: the correct roof lathing
For the construction of a roof, it would be good to have on hand design and estimate documentation with ready-made measurements, calculations and the amount of necessary materials, which will help to avoid unnecessary costs. However, not all developers turn to designers due to the considerable cost of their services. Therefore, after the selected section and the set step, you should take the necessary measurements yourself and reflect them on a hand-made sketch of the roof.
In the absence of project documentation, you need to independently draw a roof plan and apply all the main parameters to it, which will help to correctly calculate the roofing materials and avoid unnecessary costs
To calculate lumber, you will need the following parameters: the height and length of the slopes, the total length of the valleys, ridge, ribs and eaves, the width and length of all available exits, as well as the technical parameters of the selected flooring. Let's understand the calculation in detail.
Initial data: a house of 12x15 m, a four-pitched hip roof with a slope height of 10 m, a width of 12 and a length of 15 m, with two chimneys 0.6x1.4 m each and one ventilation duct 0.15x0.25 m. Eaves overhang 0.8 m, the length of the ridge is 8 m, there are no valleys, the angle of inclination is 35 °, the pitch of the rafters is 1.0 m. According to the table, a pine edged board 32x100 mm with an installation pitch of 0.3 m will be used for the lathing.
Table: dimensions of lumber for sheathing for corrugated board
|Lathing step, mm||Roof slope|
|1:1||1:1,5||1: 3 or more shallow|
|Rafter pitch 0.9 m||Rafter pitch 1.2 m||Rafter pitch 0.9 m||Rafter pitch 1.2 m||Rafter pitch 0.9 m||Rafter pitch 1.2 m|
- We determine the area of two trapezoidal slopes, which are divided into 3 figures - a rectangle of 8x10 m and two identical right-angled triangles with legs 10 and 4.3 m. Then → 2 x [(8 x 10) + 2 x (4.3 x 10: 2 )] = 246 m². Note: the lower base of the lateral trapezoidal slope in our example is 15 m, the length of the ridge is 8 m (the upper base of the trapezoid), therefore → 15 - 8 = 7: 2 = 3.5 m + 0.8 m eaves overhang = 4.3 m ( the leg of each triangle adjacent to the angle of inclination), and since the height of the roof is 10 m, it means that the legs opposite to the angle of inclination will be 10 m each.
- We calculate the area of two triangular slopes → multiply half of the base by the height → 2 x (13.6: 2 x 10) = 136 m².
- We calculate the total area of the four-pitched roof → the area of all slopes minus the total area of the openings + the area of the eaves + 30 cm at least along the perimeter of the drain. We have already taken into account the length of the eaves overhangs when calculating the area of the slopes, therefore, when calculating the total area, we do not take this value into account → 246 + 136 - (2 x 0.6 x 1.4 + 0.15 x 0.25) + 0.3 x 60 , 4 = 382 - 1.72 + 18.12 = 398.4 m².
If, according to the level of strength, a two-layer crate is stuffed, then the calculated area is doubled.
Calculation of boards for solid flooring
We will use the calculated area of the crate and the table data.
Table: number of boards in 1 m³
|Board dimensions, mm||Volume of one board, m³||Number of boards in 1 m³, pcs.|
|Note:the table is given taking into account the standard length of the boards 6 m;to find out the footage (running meters), the number is multiplied by the length of the boards / timber, or the volume of the boards is multiplied by the length and the number of boards in one cube (tabular value).|
- We calculate the area of one board with a section of 32x100 mm of a typical length, for which we multiply the width of the board by its length → 0.1 x 6 = 0.6 m2.
- Determine the number of boards → divide the total roof area by the area of one board → 398.4: 0.6 = 664 pcs. + stock 10% ≈ 731 pcs.
- We translate the number of boards into linear and cubic meters, using the values of the table → 731: 52 ≈ 14.06 m³ or 731 x 6 ≈ 4386 linear meters.
To determine the number of boards for a solid sheathing, the roof area is divided by the area of one board
Calculation of boards for sparse crate
The number of boards for a sparse structure is calculated taking into account the chosen pitch of the lathing, in our example, 0.3 m.
- We determine the volume and number of wood for the total roof area, for which we divide the area by a given lathing step → 398.4: 0.3 = 1328 m: 6 m (length of boards) = 222 pcs. Or 222: 52.0 ≈ 4.26 m³.
- We calculate the amount of lumber for the arrangement of skates, valleys and edges → the total length of the roof shaped elements is divided by the length of one board. But first, according to the Pythagorean theorem, we calculate the length of four edges, which in the hip structure are the same → 4 x √10² + 4.3² = 4 x 10.885 ≈ 43.54 m. Therefore, → 8 (skate) + 43.54 (edges) = 51, 54 m: 6 m ≈ 9 pcs. Or 9: 52 ≈ 0.16 m³.
- We find the total footage, the amount and volume of wood for the device of a single-layer sparse crate → 4.27 + 0.16 ≈ 4.43 + for a stock of 10% ≈ 4.87 m³ or 4.87 x 6 x 52.0 ≈ 1520 running meters. In this case, the number of boards will be 254 pieces. with a margin (222 + 9 + 10%).
The number of boards for a sparse crate depends on its pitch
Similarly, the cross-section and volume of rolled metal for a metal crate is calculated. The calculation of materials for the lathing is simple, and you can control the accuracy of the calculations and, if desired, fully calculate the roof, using a construction calculator on the website of manufacturers of rolled metal or lumber.
Video: a simple way of marking for trimming the crate
Step of the crate for corrugated board
Before creating a roof from corrugated board, you need to familiarize yourself with the technical properties of the selected material, since even the same brand of sheets has different characteristics that affect the rigidity of the structure.
Table: characteristics of profiled sheets
|Professional sheet brand C21||Sheet thickness t, mm||Mounting width of a sheet, mm||Weight, kg / running. m length||Weight, kg / useful m2||Workpiece width, mm||Limit deviation, mm|
|by profile height||along the profile width||along the length of the profile|
Depending on the parameters of the profiled products, the pitch of the lathing is selected, which takes into account the slope of the roof (the first table at the beginning of the article). It is necessary to comply with the laying step recommended by specialists, since the strength of the entire structure depends on this, its ability to withstand the loads exerted on it.
The ability of the roof to withstand the effects of loads depends on compliance with the installation step of the lathing
The building rules prescribe the basic norms for installing the crate in proportion to the slope of the slopes:
- at the minimum permissible angle of inclination, a solid crate is packed;
- for roofs with a steep slope (from 40 to 60º), a thinned wooden lathing is laid with a step of 300–650 mm, and for very steep slopes - up to 1000 mm;
- and the optimal lathing option is a step of no more than 400 mm, but taking into account the characteristics of the product - brand, thickness, wave height and load capacity.
For some brands of corrugated board, due to the production technology, manufacturers have provided a minimum laying step of 3000 mm. Therefore, when buying a covering material, carefully read the instructions, where this requirement is specified.
When stuffing the crate and attaching the profiled sheets to it, self-tapping screws, nails, dowels, staples are used, which also need to be selected based on the type and brand of roofing.
Video: how to fix holes in the profiled sheet if the self-tapping screw did not fall into the crate
Installation of crate for corrugated board
The installation of the lathing begins with the preparation of the material, for which the boards are sorted, the quality of the cut, the presence of defects and deflections, and also the humidity (18–20%) are checked. After that, they are treated with fire-fighting and antiseptic compounds.
It is not necessary to neglect sorting, since boards or timber of even I grade have minimal differences in thickness, as a result of which the resulting differences in level will negatively affect the quality of laying the covering material.
- The frontal strip is nailed along the eaves overhang a little thicker than the main laths, fixing it with nails in each rafter.
- On top of the upper edge of the rafter legs, waterproofing is laid from the bottom up and fixed with counter-beams stuffed along the rafters. The counter lattice performs significant functions - it evens out the unevenness of the rafter legs and creates a ventilation gap between the waterproofing and the lathing, so that the formed condensate flows down into the drip without harming the lathing and roofing. In terms of the width of the slats, the counter battens should be narrower than the rafter legs and have a thickness of 25 to 50 mm.
The counter grating evens out the unevenness of the rafters and creates a ventilation duct for the free exit of condensate
- A ridge bar is laid next, forming a ridge of the roof with a good ventilation gap for natural air circulation.
An exhaust ventilation gap is left between the battens in the ridge area, through which the air goes out, providing ventilation of the under-roof space
- The eaves overhang is made out, the mesh is laid and the bracket is fixed on each counter-rail.
The ventilation ducts of the roofing structure cannot be sewn up tightly, therefore, when decorating the eaves unit, a mesh is used that will protect the under-roof space from contamination and will not impede the flow of air
- Parallel to the ridge along the eaves, the first lath is filled, from which the selected step is marked according to the template and all the other boards of the crate are laid according to the marking. They are fixed to the rafters with nails 3 times longer than the thickness of the boards or sheathing timber. Sheathing boards are joined only along the rafters in a checkerboard pattern.
Sheathing boards are attached only along the rafters and for greater structural strength they are joined in a checkerboard pattern
- Install a drip and gutters.
After filling the lathing, the eaves assembly is finally formed - a drip, eaves strip and gutters are installed
- If the roof is gable, then the extreme gable rafters are built up so that the wind bar and the top of the wave of the profiled sheets are in the same plane. Install wind bars, which will strengthen the crate and protect the covering sheets from falling off during bad weather.
To design the gable cut, a wind bar is installed, which will strengthen the crate and protect the corrugated board from falling off during strong winds
- In places where pipes pass, the crate is reinforced with additional bars, on which aprons will be fixed in the future. In addition, they strengthen the frame or make a continuous flooring in the area of the ridge, valleys and dormers.
In especially problematic places, most of all at risk of leaks, the crate is reinforced with bars or a continuous flooring is mounted.
After assembling the structure, they begin to lay and fasten the corrugated board.
To prevent the boards or timber from bending, they are laid down with growth rings. The timber is fixed with one nail, and the boards with two along the lower and upper edges.
Video: installation of the crate for profiled sheets
Fastening the corrugated board to the crate
Corrugated sheets are attached to a crate made of wood or steel purlin. On large slopes, when several sheets are superimposed, they are connected together with overlaps, the dimensions of which depend on the slope of the roof.
The corrugated sheets are connected to each other with overlaps, the size of which depends on the slope of the roof and are fixed with self-tapping screws - in the places of transverse overlap in each wave deflection, and in places of longitudinal overlap into the crest of the wave
Table: dimensions of overlaps for corrugated board relative to the angle of inclination
|Tilt angle||Crate type||End overlap||Side overlap|
|5-10º||solid||300 mm||2 waves|
|10-15º||sparse, with a step of 450 mm||200 mm||1 wave|
|over 15º||sparse, with a step of 600 mm||170 mm||1 wave|
|Note: in case of a low slope of the roof (from 5 to 12º), the vertical and horizontal joints of the profiled sheets must be sealed with silicone or thiokol sealants.|
Video: choosing profiled sheets - length errors
Between themselves and to the crate, the sheet profiles are fastened through the lower part of the corrugation with galvanized self-tapping screws with sealing washers to prevent self-unscrewing. This fastening provides a tighter fit of the corrugated board to the base and prevents leaks at the fixing points. Self-tapping screws must be screwed in as accurately as possible, since excessive or insufficient fastening greatly reduces the performance properties of the covering material.
Self-tapping screws for fixing the corrugated board are screwed in strictly perpendicularly with a uniform force to ensure a snug fit of the covering material to the base
Ridge additional elements are laid with overlaps of 150-200 mm and fixed with an interval of 200-300 mm through the upper part of the wave. As a result, the self-tapping screws for the ridge assembly must be selected according to the formula → profile height + thickness of the sealing gasket + thread length of the self-tapping screw included in the wooden crate. To prevent the ingress of water under the ridge beam, when forming the ridge, sealing gaskets are used, leaving a ventilation gap between them and the ridge.
To avoid the ingress of water under the ridge, use sealing gaskets, maintaining a ventilation gap between them and the ridge.
The pediment is formed with a wind bar, which is fixed with the same pitch as the ridge, with overlaps of 100–150 mm extensions. The abutments of the slopes to the walls are made out with corner roofing accessories, laying them with overlaps of 150 mm for the transverse abutment and 100-150 for the longitudinal abutment, and then fixing them with self-tapping screws every 200-300 mm.
The laying of the profiles starts from the bottom corner, which is chosen so that the overlap of the sheets is located along the prevailing wind direction.
There are two methods for attaching corrugated board to the crate:
- Vertical stacking of sheets with drainage grooves. First, two sheets are placed on the crate from bottom to top and temporarily fixed. Next, the second pair is laid in the same way, and then the entire block is leveled in relation to the eaves overhang and fixed thoroughly.
- Laying three sheets without drainage grooves. They put two lower sheets on the base, then another one on top, align along the eaves overhang and fix well.
Installation of corrugated board begins from the bottom corner, selected so that all sheet joints are located along the most frequent wind direction
Video: laying corrugated board
Decking - reliable, versatile and durable - is a good choice for those who need a high-quality and beautiful roof of a house at a reasonable price. Self-laying of corrugated board does not cause difficulties, and competent installation of rafters and battens will make the roofing structure durable. The main thing is to comply with the rules and regulations based on many years of experience of professional builders, and then everything will work out.
At what distance are the rafters placed under the corrugated board?
At the design stage of a house, the rafter system of its roof, like all other structural elements, must be calculated according to special rules and methods. Only by calculating on the basis of the data on the loads, it is possible to accurately determine all the parameters of the rafter frame, which include the step of the rafters, that is, the distance between their longitudinal axes.
If the builder neglects the calculation and determines the frequency of installation of rafters "by eye", the rafter system will turn out to be either unnecessarily cumbersome and expensive, or not sufficiently strong and reliable. In the latter case, deformations or complete destruction of the rafter frame will be inevitable.
How to choose a tilt angle
The angle of inclination of the mansard roof
When choosing the angle at which the roof slopes are installed, it is necessary to consider:
- type of roofing
- rainfall and wind strength
- the purpose of the room - for a living space, the height of the ridge should not be placed below 2.5 meters.
The optimal value for the upper slopes is considered to be 30–45 degrees, for the lower ones - 60 degrees.
Roofing device made of profiled sheet - roofing installation technology
One of the advantages of corrugated board is that the length of its sheets can be different and reach 13-14 m. Therefore, on slopes of shorter length, the corrugated board can be mounted without horizontal joints and overlaps. Such a roofing device made of corrugated board significantly increases its reliability and facilitates the calculation of the consumption of materials required for the installation of roofing.
If the length of the roof slope is greater than the maximum possible length of the profiled sheet, it is necessary to order the profiled flooring so that the attachment point of the transverse joint of the two sheets falls on the sheathing board. It should be remembered that the overlap between the rows of corrugated board should be from 100 to 200 mm, depending on the slope of the roof. Neighboring sheets of corrugated board are laid with an overlap in one wave.
Arrangement of a metal roof made of corrugated board - a scheme for laying sheets with overlaps
If the above requirements are met, such a roof structure made of corrugated board ensures good roof tightness at any time of the year.
After installing the waterproofing and lathing, proceed to the installation of the corrugated board. Begin the installation of the profiled sheet from one of the lower corners of the ramp. If the corrugated board has a capillary groove, it is better to start installation from the left edge. In this case, the edge of the next sheet will cover the capillary groove of the previous one.
If the roof structure made of corrugated sheet is more complicated than the usual shed or gable roof and consists of several intersecting planes, then before starting the installation of corrugated board it is better to draw a layout diagram of the roofing sheets.
The first sheet of corrugated board is laid in such a way that it protrudes beyond the gable by approximately 300 mm. The eaves overhang above the side wall of the building should also be 300-400 mm.
Having installed the first sheet, it is temporarily fixed with one self-tapping screw. After that, with the necessary longitudinal overlap, the next sheet is installed and temporarily fastened. After mounting 3-4 sheets, the entire row is aligned along the edge of the cornice and finally attached to the crate. The edges of adjacent sheets of corrugated board are connected to each other with short self-tapping screws or rivets.
When the roof slope is less than 12-14 °, the transverse and longitudinal overlaps are sealed with a roofing sealant. Such a roof structure made of corrugated board makes it practically airtight.
For fixing the corrugated board, special roofing screws with a press washer and a gasket made of special neoprene rubber are used. Since the profiled sheet is attached to the crate through the bottom wave, the role of this gasket is very important. Neoprene rubber differs from ordinary rubber in that when the screw head is tightened, it self-vulcanizes, while remaining elastic, which absolutely excludes the possibility of water leakage at the attachment point.
Roofing screws have a special drill-shaped tip. Therefore, they can themselves make holes in the profiled sheet. But the sheets of corrugated board, with a thickness of more than 0.5 mm, are best pre-drilled in the attachment points. The hole diameter should be slightly larger than the screw diameter. This makes it possible to compensate for the linear expansion of the roof covering during sudden temperature changes.
Roofing screws have a special drill-shaped tip. Therefore, they can themselves make holes in the profiled sheet. But the sheets of corrugated board, with a thickness of more than 0.5 mm, are best pre-drilled in the attachment points.
To screw in self-tapping screws, use a screwdriver or electric drill with adjustable speed and reverse rotation. A properly wrapped self-tapping screw should firmly press the elastic gasket to the corrugated board, but the pressure washer should not be deformed.
The technology of roofing from corrugated board is so simple that it can be installed without the involvement of specialists. It is better to carry out work on laying the profiled sheet in a team of 3-4 people.
If you nevertheless decide to contact the professionals, the table below shows the approximate prices for the installation of corrugated roofing. It should be borne in mind that the cost of installation is highly dependent on the region, as well as on the season. For example, at the end of spring and summer, when the number of orders is at its maximum, the price of roofing from a profiled sheet is also at its maximum. In addition, such work in the southern regions is much more expensive than in the cold northern regions.
The total cost of the roofing device from corrugated board must include the installation of the sheathing. The price of these works is approximately 120 rubles. for 1 m².
Distance between rafters for a gable roof
Among people involved in the construction of a private or country house, there are constant discussions about the most successful roof design and the number of supporting elements. To understand these opinions and take one side or the other, it is necessary to consider the general structure of the roof.
There are two types of rafter construction:
Hanging rafters they are used on relatively small houses with a length of supporting elements no more than 6 m. The design consists of a number of trusses in the shape of an isosceles triangle. The trusses are installed on a lathing from a bar (mauerlat), interconnected by lathing strips. The bearing capacity of hanging rafters is relatively low, but the simplicity of the structure, the economy and the high speed of installation are their advantages. There are quite a few options for the implementation of hanging rafters, which is explained by the prevalence of small buildings that do not need a complex and massive roof structure.
Hanging rafters Source stroidominvest.ru
Design layered rafter system somewhat more complicated. A strong timber - Mauerlat - is laid along the perimeter of the ceiling of the upper floor. Two (or more) vertical posts are installed along the longitudinal central axis, the height of which determines the angle of inclination of the slopes. A ridge girder is installed between the posts, which runs along the entire length of the roof and serves as a reference line for the rafter legs. Each of them has two points of support - at the bottom it is a Mauerlat, and at the top there is a ridge run.
For the formation of additional support, eliminating the sagging of the supports, struts are used - inclined strips attached to the rafter legs at an angle close to a straight line and abutting in the lower part against the central lower bar - a bed.
The lathing is installed on the outer surface of the rafter legs, forms an inclined plane, which serves for the installation of the roofing. Source: repairblog.ru
The lag step for the roof is the distance between two adjacent rafters. It is determined by the number of lags, evenly distributed along the length of the longitudinal axis of the roof. The main supporting structures for the roof are rafters and lathing, which form inclined surfaces with a given geometry and area. The angle of inclination determines the wind and snow loads, and, with an increase in the angle, the wind load increases, and with a decrease, the snow load on the roof.
The tilt angle determines the wind and snow loads Source kabel-house.ru
There are two options for roofing when laying corrugated board:
- The first one is pitched roofs, which are mainly used for the construction of utility structures.
- The second type is gable, they are mainly used to cover residential buildings. The slope of the roof for different types of buildings varies from 0 to 60 degrees. The design diagram must be well thought out and calculated.
The main components of the lathing are wooden beams, laid with perpendicular slings with a certain pitch. They are fixed mainly with nails. With a properly executed structure, the roof will be strong and will distribute the load evenly.
The main board in the crate is placed along the cornice, its thickness should be thicker than other boards. In addition, where additional roof elements such as chimneys, ventilation and a fire hatch will be taken out, additional boards must be attached. The lathing itself is attached after the insulating layer has been laid under the corrugated board and ventilation has been removed. The calculation of the thickness is carried out taking into account the height of the profiled sheets and the length of the fasteners that hold the profile outside.
The lathing is recommended to be done with a step of thirty centimeters or less, for the correct calculation of the step, one must not forget about the profile section and the thickness of the material, with a decrease in the roof angle, the distance between the lathing boards should also decrease.
At the ends on both sides, it is required to install wind boards, it is assumed that they are located above the main lathing exactly as high as the corrugated board will rise. In addition to the above factors, the climatic conditions of the region, implying certain loads from snow and hail, as well as the roof slope you choose, affect the stride length. Separately, it should be said about the creation of a possible gap aimed at fighting the wind. The withstanding load is directly dependent on the height of the profile: the higher the height, the more load the structure can withstand.
If the angle of inclination of the roof is up to fifteen degrees, a corrugated board of the C20 type is usually installed, while a continuous crate is used, and the profile sheets themselves are overlapped, in two waves. When using a profiled sheet of type C35, the crate will be constructed with a step of thirty centimeters and an overlap in one wave. Sometimes a step of sixty-five centimeters is possible, but this significantly reduces the value of the permissible load. A pitch of fifty centimeters is used for corrugated board type C44 or higher.
For the prevention and safety of the wooden elements of the sheathing, the boards should be treated with specialized antiseptic compounds. This step will keep the wood from spreading mold and also keep it safe from insects and pests. This step is optional, but if you want your roof to last longer, this tip is recommended.
The main fastening material for fixing the corrugated board to the roof is a self-tapping screw specially designed for this purpose. It is a kind of bolts with a drill at the end, and also has a special rubber gasket near the head. To maintain the style of your roof, the caps on the self-tapping screws have colors similar to those of the corrugated board.
Self-tapping screws attach the corrugated board to the crate only in the lower part of the wave. It is also possible to use roofing nails and V-shaped fasteners as fasteners. Each method has its own advantages and disadvantages. It should be noted that nails perform well their function when attaching corrugated board as protective shields, as well as for wall cladding. V-shaped fasteners are used to fix the profile sheets as a ceiling.
Profile sheets are stacked in the direction from the bottom row to the top. It must be remembered that the first row of sheets should protrude eight to fifteen centimeters from the wall in order to protect it from the unwanted effects of moisture.
Under the lathing, it is customary to understand the base for the roofing material, made of a metal profile or wooden slats, the laying of which is made in the perpendicular direction relative to the rafters.
The roof lathing for corrugated board takes the load from the roof covering, distributing it between the rafters, which helps to avoid premature deformation of the roof. Installation of profiled sheets can be carried out on a solid crate or made with a certain step, depending on the technical characteristics of the material.
The following can be used as material for the manufacture of the lathing:
- Wood. This is the most common option for the manufacture of sheathing for corrugated board. The lightness and strength of natural wood contribute to the creation of strong and reliable structures. Such a base is made from boards with cut or uncut edges. A board for a sheathing for a corrugated board can have a width of 15 cm and a thickness of 4-5 cm. The disadvantage of wooden products is considered to be easy flammability and poor resistance to water, which causes a rapid loss of strength. Treatment of the material with waterproofing agents and fire retardants helps to solve the problem.
- Metal. In the construction of industrial premises, a metal profile is most often used. Such elements have no length restrictions and are characterized by increased strength with low weight. The metal lathing for the corrugated board can be installed in steps of up to 1.5 meters. Despite the fact that exposure to water can cause corrosion on metal products, they still have a longer operating period compared to wooden structures.
How to do - instructions for implementation ↑
Base for profiled sheet and steam and waterproofing ↑
If the roof is arranged in a heated room, then usually steam and waterproofing membranes are included in the composition of the roofing cake. As a rule, these are layers of film that are laid with an overlap on the mounted rafters with an overlap on the walls. In such cases, the construction of the base becomes a little more complicated - the transverse beams are not nailed onto the rafters themselves, but onto longitudinal beams, which are additionally mounted to secure the film.
How to make a construction device yourself ↑
Having completed the calculation of the sheathing for the corrugated board, they buy material - beams made of pine, spruce, oak, etc. It must be well dried, without warping and straightforward.
This is a rather important nuance, if the straightness of the bar is violated, it must be corrected.
The material is treated with an antiseptic that protects the wood from damage by fungi and microorganisms, as well as fire retardants.
It is advisable to carry out the processing on a structure that has not yet been installed in order to reduce the likelihood of the formation of unimpregnated areas.
First, mark the location of the upper (at the ridge) and lower boards or transverse beams of the base and then the attachment points along the entire slope. If a bulge or depression is found in these places, it is squeezed or stuffed with slats or roofing material of the required thickness.
Installation of the rest of the base elements is performed from the bottom up. To control the correct position of the beams and their parallelism, a stretched line is used.
A wooden base for a profiled sheet is quite often spliced along the length, since its standard size for sawn timber is usually not enough for the length of the slope. The edges of the spliced parts are first fastened with nails, then installed on the roof in such a way that the joint of the timber falls on the rafters. In adjacent horizontal rows, the joints should not coincide. To move them, the boards are cut to a specific length.
Wind boards are installed at the ends of the roof. In height, they should be greater than the base by the height of the profiled sheet profile.
A separate base structure is installed under the chimneys or all kinds of parapets passing through the roof.
It is better to carry out installation work in dry weather, so that wet beams or baseboards for a metal profile do not deform from excess moisture.