Rafter Sizes And Spans

Pergola rafter spans for 600 mm and 900 mm spacing.

Rafter sizes and spans. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. The lengths and sizes of joists vary depending on the species and quality of the lumber used. The beam span length is fixed for this demo version. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.

Rafter spans c24 strength class timber. Rafter spans for southern yellow pine douglas fir and eastern spruce. The full version allows you to design beams of any size. Building control guidance note subject purlin and rafter roofs timber sizes and construction details 18 issued 010413 rev page 1 of 2.

Surveyors span tables for designing roof rafters. Rafter span tables for surveyors roof construction. For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.

For pitched roofs flat roofs and ceiling joists. 2 for design parameters refer to figure 726. Pitched roof timber sizes. 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.

So if your house is 26 feet wide and the roof ridge beam is centered on the house you will need a rafter that can span 13 feet. Other more complex load condition spans can be determined with our free hyne timber design 75 software. Span tables allow users to choose an appropriate size and stress grade to achieve spanning needs. Calculations to bs 5268 2.

Rafter and joist span faq. Lets use this example and find a size of rafter that will work. For simple construction such as domestic construction this can be determined from span table supplements in as16842 and as16843. Wind classification n1 n2.

Surveyors and structural engineers utilise data from tables below to help calculate the correct size. Spanman increase member sizes in accordance with australian codes if the member supports brittle loads. If the manual load is one of the types in the drop down box please selecet this type or leave the setting at standard material if the load is not brittle. 3 where rafters are equal to or exceed four times their breath blocking should be used to reduce distortion.