Roof Rafter Centres

Building roof with rafters.

Roof rafter centres.

If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. Not only you will need to be able to determine the size of material lumber to use based on spans between supporting headers roof pitch and snow loads but also to pre cut each rafter to exact length and angle. But they do tend to space rafters in one of several industry standard increments typically. It is often used in simple roof trusses such as in the shed porch and garage.

For pitched roofs flat roofs and ceiling joists. Setting out rafter lengths with a ready reckoner. Rafter and roof joist spacing is only one part of a complex roof design that works together to form a structure that meets building codes and can hold up the weight of the roof and roof load. Drag the centres or total length slider to see the effect of double end members.

With equal spacing centres are adjusted to fit equally at nearest to under entered centres. 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. I prefer 16 on studs and joists with rafters at 24 joists stack next to studs and rafters stack directly over studs 24 o c. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.

Builders aren t bound by standard rafter spacing measurements. If you re stuck with an end gap that s too small or double end members try adjust both ends equally to open and spread the gap to each end. Typical roof truss spacing means that they are usually about 24 inches from centre which means at the centre of one truss there will be a two foot gap or twenty four inch gap until the centre of the next truss. Unlike ordering ready made trusses building a rafter roof will require properly sized and pre cut rafters.

The king post roof truss is the simplest of the trusses because of its simple composition. Surveyors span tables for designing roof rafters. These standards are as follows. Rafters stack over studs every other rafter layout or 48 o c.

You don t need a framing square or rafters to calculate the rafter lengths you can do it all on paper allowing you to calculate all the materials needed to price the job accurately just by knowing the size of the roof and the centres for the rafters. It is always better to have a large rafter rather than be concerned with a sagging roof.