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# The cross section of the rafters and sheathing: the optimal size for the types of roof

In order to calculate the truss system of the roof of the man who is not familiar with all the nuances of complicated design calculations according to SNIP and other standards can use our construction calculators roofs.

As the original settings, you must enter the details of certain elements of the truss system:

• to specify pitch of rafters (the distance between step adjust system load of the rafters),
• the size of the rafters, the so – called cross-section = thickness x width of Board or timber

It is worth to say that the Board is a more affordable option for your roofing system as it can withstand the load and, importantly, is at times low cost.

The two tables below we have collected frequently used in the construction sizes of the rafters and crates by types of roofing. The minimum angle of the roof also provides optimal depending on its type, something which the angle specified is the minimum, but according to SNIP.

The most frequently used parameters of the elements of the truss system - pitch and cross-section rafters, roof slope, depending on the type of roofing material:

 Type of roof The optimal roof slope degrees Step rafters, cm The cross section of the rafters, cm Corrugated sheet 12 Min (value 20-30) up to 100 cm Board 5 x 15 Onduline 15 60 -90 Board 5 x 20 Cement-sand tile 22-30 ≤ 75; ≤ 90; ≤ 110 Board 5 x 15 ceramic tile 22-30 60 - 80 Board 5 x 15; 6 x 18 soft roof (membrane; shingles) 7 60 - 150 cm Board 5 x 15 Metal 15 60 - 95 cm Board 5 x 15; 5 x 20 (for insulation) Slate 14 - 60 80 - 130 cm Board 5 x 15; 5 x 15 asbestos cement sheets of ordinary profile asbestos cement sheets of the unified profile

To make the calculation of rafters a gable roof in automatic mode will help you calculator of rafters on our website.

The following table contains data on the crate, the counter lathing and the material of the roof:

 Type of roof Shelter. material Length x width x thickness, mm Roof pitch, degrees The step of sheathing, see The cross section of the sheathing, see Counter-lathing, sm (step = step rafters) The overlap shelter. sheets, see Corrugated sheet: 12 Min (optimum 20-30) accordingly, the angle Board 3 x 10 the width of the beam is slightly less than rafters with thickness of 2.5 - 4 horizon. overlap: the angle of the roof is less than 15° - 20 cm;15-30° - 15 -20;from 30° - 10 -15 HC-20 thickness 0,55 30; 45 40; 60 0,75 30; 45 50; 70 NA-35 0,55 30; 45 100; 100 0,75 30; 45 120; 130 S-44 0,55 30; 45 90; 150 0,75 30; 45 110; 140 Cement-sand tile and ceramic tile from manufacturer and type 22 - 30 31,2 - 33,5 the lumber from the stage rafters:3 x 5; 4 x 5; 4 x 6 or 5 x 5 3 x 5 8,5 - 10,8 30 - 90 Of 32.1 to 34.5 Board 5 x 15; 6 x 18 7,5 - 10,8 soft roof (membrane; shingles) from the manufacturer 7 1. roll - on solid sheathing 3 to 5 mm gap;2. soft tile - 30 cm step boards OSB sheathing under 1.solid2.sheathing Board 2.5 x 10-15 + OSB 9mm 3 x 5 for roll - 15-30; for soft tiles - 15 Metaltile Optim. 4500 x 1160 - 1190 x 0.5 height 1.8 - 2.5 cm step wave 35-40 cm 20 80 - 100 (waves) Board 5 x 20; 4 x 6 timber 3 x 5 depending on the brand of 6 - 9 Slate 3600 x 1500 x 8-10 3000 x 1500 x 8-10 2500 x 1200 x 6-8-10 14 - 60; Optim. 25-45 the sheet should be based on 2 timber batten 3 x 5 from 12 to 30 asbestos cement sheets ordinary. profile 50 - 54 Board 5-6 x 10;bar from 5 x 5 overlap wave asbestos sheets unific. profile 60 - 75 Board 5-6 x 10; beam 7.5 x 7.5 bitumen corrugated sheet (evroshifer) - for example, Onduline 2000 x 950 x 3 wave height 36 5 - 10 5 continuous (gap up to 5 cm) 3 x 5 3; side 2 waves 10 - 15 45 Board 5 x 20; timber 4 x 5; 5 x 5 2; side 1 wave 15 60 Board 5 x 20; timber 4 x 5; 5 x 5 1,7; side - 1 wave

In order to define the dimensions of the entire system of rafters is necessary to make calculations of the main effects of wind, snow mass, and the weight of the roofing materials and structural elements of the roof together.

Check the procedure for load calculation in the article "Calculation of the rafter system".

Again we remind you that the calculation is given for reference in a much simplified format as for exact calculation it is necessary to consider the vertical and horizontal loads on the truss legs, expect further resistance of the rafters to bend, stretch and compression, to check the designs on the ability to resist chipping and crushing.

If you have not arhitekturna complex design, you may be able to build the roof yourself, based on the optimal size of timber or boards, standardized design parameters of the roof.

The figure and the table below shows the standard section of the elements of truss construction:

 Span (m) 2,0 2,5 3,0 4,0 4,5 5,0 5,5 6,0 6,5 7,0 Installation step (m) 0,6 75х100 75х150 75х200 100 x 200 100 x 200 125х200 150x200 150х225 150х250 150х300 1,0 75х150 100x150 100х175 125х200 150x200 150х225 150х250 175х250 200х250 200х275

Again, in a simplified format to calculate the ability of the roofing system to withstand loads capable of that.

Aboutnlin roof calculators will help you calculate the amount of lumber, roofing and roofing materials for the construction of the roof and roof system and the parameters of the roof, sheathing and rafters.

Thus, you can roughly estimate how much construction materials you need to buy, how and how much will be the sheathing and rafters.