How Far Apart Are Joist In A Flat Roof

2 6 shed roof rafters are enough for nearly any type of shed a homeowner wants to build.

How far apart are joist in a flat roof.

This is a way of measuring the degree of steepness of the roof. In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart. An syp 2 6 rafter at 24 o c. While a 2 6 might be nearly double the cost of a 2 4 you can likely space the 2x6s further apart negating the added expense of increasing your lumber width.

Although 2 inch by 6 inch lumber is used most often in ceiling construction to support 5 foot by 8 foot sheetrock the material commonly used for ceilings other sizes of lumber may be used such as 2 inch by 4 inch and 2 inch by 8 inch lumber. Builders aren t bound by standard rafter spacing measurements. Theseoverallspansarebasedonnds 01 with 4 nominal bearing each end 24 o c. 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.

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. The number of inches that the roof rises vertically for every foot of roof. Can span up to 13 4. A roof joist is always spaced no more than 16 inches apart from another roof joist.

To build a roof joist for a flat roof you need some carpentry skills and a few basic tools. Im building a summer house shed. 2 by 4 inch lumber. But they do tend to space rafters in one of several industry standard increments.

Roof type 55 1 15 40 snow shingle 55 1 15 30 snow tile 47 30 snow 40 20 snow 1 25 20 construction or rain not snow load 55 1 15 40 snow 47 1 15 30 snow 40 1 15 20 snow 40 1 25 20 rain or constn. The size of the ceiling joist also is accounted for in joist spacing. If the roof is not completely square you can decrease the space between joists but never increase the space. Measure from the ends.

The pitch of the roof is a ratio. The roofing surface is installed over the joists while insulation is placed between them and the ceiling beneath is suspended from them. The drawing is attached its 4 8m x 8m the front height will be around 2 5m and the back 2 2m. So use a tape measure to find the height of the roof above the top wall of the building.

Span calculator for wood joists and rafters also available for the android os. Total load psf duration factor live load psf notes.