Timber Roof Purlin Sizes

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.

Timber roof purlin sizes.

All about purlin span for metal roof. Wood timber are sawn into various sizes amongst are. J l neal subject. Maximum clear span of rafters in metres for roof pitches of between 15 and 45 degrees.

2 by 2 i e 50mm by 50mm. Surveyors span tables for designing roof rafters. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Purlins near roof edges or changes of roof slope are subject to higher wind forces than interior purlins.

Purlins are spaced based on designs or type of roofing sheets. This is the distance between rafter centres. 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. You don t have a nailing surface on the end of a 1x4.

2 by 4 i e 50mm by 100mm. 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. Usually 400 450 or 600mm but any value can be used up to 610mm max. But for our calculations we are using 900mm.

Purlin and rafter roofs timber sizes and construction details author. It is suitable to use for roof sheeting from fiber cement. Roof pitch between 15 and 22 5 degrees with rafter spacing strength. 2 by 3 i e 50mm by 75mm.

All the figures are based on roofing tiles or slates laid on. Roof pitch between 15 and 22 5 degrees with rafter spacing strength class c16. They both can be combined well to make sure that the space below the roof. Building control guidance note purlin.

If so you should use dimension lumber like 2x4. Purlins are the wood of 2 by 2 or 50mm by 50mm we nail the roofing sheets on.