Porch Roof Rafter Spacing

The minimum pitch for a roof is 1 4 12 which translates to 1 4 inch rise to 12 inches of run.

Porch roof rafter spacing.

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. In general the maximum span for a 4 by 6 beam is 6 feet between 4 by 4 posts. However you can only use this pitch with built up roofing or specialized synthetic roofing. An essential part of planning a patio roof or gazebo project is determining the number size and spacing of rafters beams and posts according to the loads they will carry.

If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. Double the hill and valley width since this is the amount that the panel will overlap the one next to it on each side. Once the beams are in place mark the spacing for the trusses normally 16 inches apart. 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.

If your local building authority has a rafter spacing code you may not space rafters wider than required by code. Subtract that number from the width of the panel and then divide by 2 to come up with the spacing for the rafters. Rafters must be strong enough to hold the roof sheathing and the shingles. The same concept holds true for roof trusses.

So the space between rafters can be greater without reducing the maximum span. A 4 by 10 can usually span up to 12 feet between posts. Typical rafter spacing codes will specify a minimum spacing of 16 inches 19 2 inches or 24 inches. Squaring the beams and bracing them to ensure the maintain square is essential to the roof building process.

Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet. Keep in mind that these figures depend on the size and spacing of joists and the overall structural loads. Both 16 inches and 24 inches are common measurements for rafter spacing. This table agrees that 10 12ft is the max span for typical grade lumber at typical spacings for a 5psf dead load.

Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.