Roof Rafter Centres

Builders aren t bound by standard rafter spacing measurements.

Roof rafter centres.

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. 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. 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. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.

Building roof with rafters. Drag the centres or total length slider to see the effect of double end members. For pitched roofs flat roofs and ceiling joists. 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.

It is often used in simple roof trusses such as in the shed porch and garage. Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch. In a nutshell it s made up of a central vertical post called the king post two rafters meeting at the apex and a tie beam or the horizontal base. The king post roof truss is the simplest of the trusses because of its simple composition.

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. Either 24 or 16 centers on rafters is typical or common practice. With equal spacing centres are adjusted to fit equally at nearest to under entered centres.

Surveyors span tables for designing roof rafters. 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. Setting out rafter lengths with a ready reckoner. These standards are as follows.

It is always better to have a large rafter rather than be concerned with a sagging roof. Unlike ordering ready made trusses building a rafter roof will require properly sized and pre cut rafters.