Roof Post Spacing

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.

Roof post spacing.

With just rafter load. Rule of thumb a beam can span about one foot for every inch of depth. A 4 by 10 can usually span up to 12 feet between posts. If you move up to 4 by 8 you re usually allowed to span up to 10 feet between posts.

A double 2x12 beam can span 12 feet. Roof purlins are 2x4 2x6 or 2x8 lumber that spans between the trusses to provide framing for metal roofing or roof sheathing. Engineers have since determined however that the physical design of a post frame building will allow for standard spacing as great as 12 feet from the center when using high quality metal connector plates and lumber. The most efficient post spacing is going to depend upon the wind and snow load conditions at any particular given pole building site.

Doesn t mater what size the posts are the spacing is governed by beam size and roof load roof slope plays a part in the loading of the beam. Roof trusses were usually produced on site in the past. Spacing will vary be design and roof load but usually 24 on center or less. In general the maximum span for a 4 by 6 beam is 6 feet between 4 by 4 posts.

When supporting joists that span 12 feet with no overhang beyond the beam a double ply beam can span in feet a value equal to its depth in inches. 2x12 doubled can span 12 normally. May be attached above the trusses on edge or flat or between the trusses using post frame anchors or joist hangers. Beams can be solid lumber or be built from lengths of 2 by lumber nailed together with 1 2 inch pressure treated plywood spacers in between this forms a 3 1 2 inch thick beam that is equal to the width of a 4 by post.

Dimensional lumber deck beam span chart the numbers in gray indicate the distance between the support posts. Never place concrete next to wood. As a general rule the best bang for your buck is most typically spaced every 12 feet although 10 foot and 14 foot spacings are often a close second. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope.

Use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size.