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Gandalf 04-18-2010 03:21 PM

Attached Patio Overhead Roof
I am installing a 9' high patio roof on a 5 1/4" slab. The roof will be attached to a house wall. The area is 10 1/2' along the house wall and if I put a shed roof on a ledger the span is 9' from the ledger to the 4"x4" posts. I will use a 2" x 6" ledger. The roof will have about nine 2"x4" rafters on 12" centers and 3/4" OSB sheeting plus the weight of a layer of asphalt 3-tab shingles.

How many 4"x4" posts do I need to support this span?

Also, if I decide to make an attached gable roof instead would I need the same number of 4"x4" support posts.

Ron6519 04-18-2010 03:28 PM

The structure you describe is inadequate for the job, even in a southern region. The 2x4 rafters are inadequate. for one. It would help if you posted where you live.


Gandalf 04-18-2010 05:00 PM

In Denver Colorado. Why inadequate? The IRC codes say that with a 30 psf ground snow load that 2"x4" rafters on 12" centers can span 9'5".

Scuba_Dave 04-18-2010 06:00 PM

What type/grade of wood are you using to get the 9' 5" span ?

Gary in WA 04-18-2010 10:53 PM

You may want to give a call to your local Building Department.... My 2003 IRC says 2x4, 12"o.c., Douglass fir, will span 9'10" with NO SNOW load.

Be safe, Gary

Gandalf 04-19-2010 10:30 AM


Originally Posted by Scuba_Dave (Post 430347)
What type/grade of wood are you using to get the 9' 5" span ?

It is the douglas fir they sell at home depot.

Scuba_Dave 04-19-2010 10:54 AM

I'm getting only 7' 6" for span w/30psf snow load
2x6 will get you 10'+ easily with 16" OC

Gandalf 04-19-2010 11:43 AM

Thanks Dave. So that's about 9 ten foot 2 x 6 boards. How many 4" x 4" support posts do you think I should use?

Scuba_Dave 04-19-2010 11:53 AM

You are coming out ~9' 5" from the house ?
For 2x6 rafters use a 2x8 ledger & hangers for better support
If your roof will be 10' 6" along the house you really only need (2) posts at the outside corners
Instead of 4x4's go to 6x6's or 4x6 at the very least
Cut & notch the top & run a beam between the 2 posts to support the rafters
What kind of slope will you have on this roof ?
Low slope I'd probably go to 2x8 rafters for that one heavy snow storm

Since this will be attached to the house you are supposed to dig down & pour piers for the posts to sit on - down below frost depth for your area

Pics might help to see what you are dealing with

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