Roof Rafter Centres

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.

Roof rafter centres.

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. Surveyors span tables for designing roof rafters. 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.

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. It is often used in simple roof trusses such as in the shed porch and garage. Either 24 or 16 centers on rafters is typical or common practice. Rafters stack over studs every other rafter layout or 48 o c.

Drag the centres or total length slider to see the effect of double end members. These standards are as follows. Builders aren t bound by standard rafter spacing measurements. But they do tend to space rafters in one of several industry standard increments typically.

With equal spacing centres are adjusted to fit equally at nearest to under entered centres. 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. Setting out rafter lengths with a ready reckoner.

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. 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. 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. 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.

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