Roof Post Spacing

Dimensional lumber deck beam span chart the numbers in gray indicate the distance between the support posts.

Roof post spacing. 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. With just rafter load. 2x4 doubled can span 4 etc. A double 2x12 beam can span 12 feet.

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 purlins are 2x4 2x6 or 2x8 lumber that spans between the trusses to provide framing for metal roofing or roof sheathing. In general the maximum span for a 4 by 6 beam is 6 feet between 4 by 4 posts. Rule of thumb a beam can span about one foot for every inch of depth.

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. May be attached above the trusses on edge or flat or between the trusses using post frame anchors or joist hangers. Never place concrete next to wood. The most efficient post spacing is going to depend upon the wind and snow load conditions at any particular given pole building site.

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. 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. 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.

Spacing will vary be design and roof load but usually 24 on center or less. A 2 2x10 can span 10 feet and so on. 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. Roof trusses were usually produced on site in the past.

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.