Timber Roof Purlin Sizes

For pitched roofs flat roofs and ceiling joists.

Timber roof purlin sizes.

Roof pitch between 15 and 22 5 degrees with rafter spacing strength. Roof pitch between 15 and 22 5 degrees with rafter spacing. J l neal subject. 2 by 3 i e 50mm by 75mm.

If so you should use dimension lumber like 2x4. 2 by 4 i e 50mm by 100mm. All the figures are based on roofing tiles or slates laid on. 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.

The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Usually 400 450 or 600mm but any value can be used up to 610mm max. Roof pitch between 15 and 22 5 degrees with rafter spacing strength class c16. This is the distance between rafter centres.

As per as1684 and as4055 spanman adopts a nett pressure coefficient applied along the full length of the purlin of cpn 2 0 for non cyclonic zones n1 to n6 and cpn 2 5 for cyclonic zones c1 to c4. Now if you are strapping the rafters 1x4 pt is usually used set at 2 intervals or closer and you double the first one at the edge of the metal. Wood timber are sawn into various sizes amongst are. Surveyors span tables for designing roof rafters.

Purlins near roof edges or changes of roof slope are subject to higher wind forces than interior purlins. All about purlin span for metal roof. But for our calculations we are using 900mm. It is suitable to use for roof sheeting from fiber cement.

Purlins are the wood of 2 by 2 or 50mm by 50mm we nail the roofing sheets on. Building control guidance note purlin. Purlins are spaced based on designs or type of roofing sheets. You don t have a nailing surface on the end of a 1x4.

Maximum clear span of rafters in metres for roof pitches of between 15 and 45 degrees. They both can be combined well to make sure that the space below the roof.