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Post Spacing and Overhangs

We have had many inquires regarding post spacing for our Alumawood patio covers. You may find the post spacing in the engineering on the “Resources” page at alumawood.com.

The maximum post spacing for an Alumawood patio cover varies depending on many factors. The projection of the cover, the overhang, the type of cover, the type of header being used, the snow and wind loads all effect the post spacing.

In the engineering the “Tributary Width” is used to calculate post spans, footing size gauges of aluminum needed, post type, etc. To calculate the Trib width you may use the chart found in the engineering on sheet 3 of 21 for the Newport (solid) or sheet 3 of 9 for the Laguna (lattice). Simply find your overall projection (that runs across the top of the chart) and the desired overhang past the posts and header (running down the left side of the chart) and find where they intersect on the chart, this is your “Trib Width”.

Once you find your Trib Width you go the the chart with your snow (or live) load, wind load and type of header. Standard covers are 10lb snow load and 90 mph wind load with a 0.042 x 3″ x 8″ box beam. Find this chart, find your trib width and your maximum post spacing is to the right of it.

You will find that many times, with the maximum post spacing, you will not need to set the post that far apart to work for your cover. You will have some “leeway” in placing your posts, just stay within the maximum post spans

You will also have leeway in determining the side overhang. This can never be more than 25% of the maximum post span. A 20′ post span can have a 5′ side overhang, whereas a 4′ post span will have only a 1′ side overhang.

Remember to take into account the aesthetics of your cover when determining the post placement of your Alumawood patio cover. The decorative Corbel and Scalloped ends look better with a 18″ overhang. If you are using large columns you may want even a 24″ overhang. Check out our picture gallery and notice some of the different overhangs.

Above – side overhang too short, projection too big?

Above – side overhang good, overhang (projection) too short

Above – nice balance of overhangs

Regards, Robert Pinnell
contact@alumawood.com
1-888-alumawood (258-6296)
www.alumawood.com

This entry was posted on Saturday, March 29th, 2008 at 11:10 pm and is filed under Tip & Ideas. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.