Timber Sizes For Pitched Roof

The building control officer won t specify the timber sizes but seems to be easy going and would be happy to accept generous sizes with c24 timber.

Timber sizes for pitched roof.

The pitch of the toof is significantly increased to provide additional strength and durability as well as providing a better internal space. My builder would also be delighted to over specify the timber. Roof pitch between 15 and 22 5 degrees with rafter spacing strength class c16. A new timber ring beam is fitted alongside the existing windows to support the new roof structure.

It will be all be warm roof insulation above and between with the ceiling plasterboard nailed under the rafters so no ties. Rafters are nailed to a wall plate at the top of each supporting walls these are normally 100x75mm 4x3 inches timber embedded on cement mortar on top of the inner skin of a cavity wall or the inner part of a solid wall. Surveyors span tables for designing roof rafters. 9 5mm plasterboard should be fixed at a maximum support spacing of 450mm.

For pitched roofs flat roofs and ceiling joists. Surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings. Plasterboard should be fixed as follows. Roof pitch between 15 and 22 5 degrees with rafter spacing.

The wider the gap between the rafters the thicker the rafter and lath timbers need to be. Ceiling finishes should be fixed according to the spacing of the support members and the thickness of the sheet. 12 5 15mm plasterboard should be fixed at a maximum support spacing of 600mm. C16 timber is commonly used in floor and roof joists for internal building work.

It s often chosen as the standard timber for roof extensions or joist refurbishment as it s the most cost effective internal structural timber. Maximum clear span of rafters in metres for roof pitches of between 15 and 45 degrees. Maximum clear span of rafters in metres for roof pitches of between 15 and 45 degrees size of rafters in mm roof pitch between 15 and 22 5 degrees with rafter spacing of roof pitch between 22 5 and.