Timber Roof Beam Sizes

Here s how to calculate the size of a timber beam you need to span a given distance.

Timber roof beam sizes.

A 8x12 beam will net an overall 7 x 11. Starting from scratch with no previous knowledge of structures required. These spans were calculated using our flat roof joist calculation. Aitc capacity tables provide the uniformly distributed load that a glued laminated timber beam can support based on beam size span and material properties.

For simple construction such as domestic construction this can be determined from span table supplements in as1684 2 and as1684 3. This tells you the size of the beam needed to support the porch s roof. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Calculate the initial value for d then round it up to the nearest inch.

Most interior beams need to include the roof load. If there is are any questions about anything else then you should contact your supplier or an engineer. Per wwpa guidelines for standard dimension timbers a nominal 4 x6 timber nets to 3 x5 actual dimensions after it has been sawn all beams larger than 8 inch will mill to the inch. These tables are provided as a guideline.

Click on a span to generate a full calculation you can adjust the exact span. Pitched roof timber sizes. In the example d calculates to 7 75. Table specifications are provided with each table indicating conditions and assumptions used to calculate the loads.

Stress grades and timber sizes combine to determine the spanning ability of load carrying members. Span tables allow users to choose an appropriate size and stress grade to achieve spanning needs. This means the example porch would need a 6 inch by 8 inch beam. 1 2 timber strength class and joist size automatically calculate sizes suitable for supporting the loads below c16 cost effective for most applications c24 stronger more demanding c14 c18 c22 c27 c30 c35 c40.

All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. It has been my experience to never use a beam smaller than a two ply 2 x 8. This span table is to the format and methodology given in bs 5268 7 2. This calculator matches up with 90 of the applications in the 2012 international residential code book.

Aitc beam capacity tables.