Truss Spans Posts For Patio Roof Cover

by Marshall
(Lebanon, Ohio)

I would like to know if there is a chart that shows the span of 2x6's,4x6's.4x8's etc. I want to build a cover over a patio with the least amount of posts possible. The patio is 14' out from house and 17' wide with a simple slight pitch plywood roof with asphalt shingles.

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Mar 02, 2008
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Building a Patio Roof Cover
by: Rich Bergman - Editor

To give you the absolutely correct engineering answer to your question requires using some engineering software. I have used the software from www.constructioncalc.com as it does all of the weight distribution based on size and species of lumber etc.

However, you probably don't need to be quite so precise because your structure is a roof only and will not be holding a heavy load - other than the occasional dumping of snow which can happen from time to time in your area.

So snow loads are determined locally by the town or municipal building department which you should visit. The lower the pitch the stronger the trusses/joists have to be ie 2x8 may be required rather than 2x6 over a 17 foot distance.

Having said that, you could just over build. This would involve probably 2x8 trusses set at 12" on center and the support beam made of 3-2x8s laminated together set at 12' from the house so the eaves overhang is about 24".

As I say, go to your local building dept for the snow load info to confirm but what I just described would be very strong as I build houses with roofs that are made of 2x4 trusses.

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