How Far Apart Are Joist In A Flat Roof

Im building a summer house shed.

How far apart are joist in a flat roof.

For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. But they do tend to space rafters in one of several industry standard increments typically either 12 16 or 24 inches apart. Span calculator for wood joists and rafters also available for the android os.

If the roof is not completely square you can decrease the space between joists but never increase the space. 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. Variations in ceiling construction nonparallel ceiling joist designs require additional support construction in the ceiling. Joist spacing of 24 inches is allowed for spans between 16 to 20 feet using 2 inch by 10 inch lumber of these three grades.

Wane as allowed in bs 4978 2007 a2 2017 is permitted in all sections included in these span tables. In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart. Also available for the android os. I m told i should use 6 meter 9 x 3 c24 roof joists.

Holes drilled at the neutral axis centre line are not to exceed 0 25 of the depth of a joist and are not to be less than three diameters centre to centre apart and are to be located between 0 25 and 0 4 of the span from the support. This is the distance between joist centres. The drawing is attached its 4 8m x 8m the front height will be around 2 5m and the back 2 2m. A roof joist is always spaced no more than 16 inches apart from another roof joist.