Looking for ideas for covered porch

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Old 08-16-15, 04:07 PM
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Looking for ideas for covered porch

I would like to get some ideas for my patio cover design. I have attached a picture of the house where the patio cover would be attached. I have checked out the header over the existing porch opening and found that it's a double 2x12 header. I have talked to a few contractors and their proposals are all over the place (for both design and price). A couple of them said attaching a ledger to the existing porch header would be no problem, while some say they could not, and one said an engineering report might be needed.

The patio cover would be about 14ft wide and 12ft deep. The size of the opening you see in the photo is 160" (13'-4"). The added porch cover would be post and beam construction, and I plan to use DF#2 all around. The rafters would be 4x6 and outer beam 6x8, probably 14ft with 2ft cantilever. The rafters would bear on the outer beam and overhang by 2ft. Posts would be 6x6.

So, there are a couple of constraints here:

- LEDGER ATTACHMENT: There is no band joist to attach to, only the header of the existing built-in porch. This porch is part of the house framing but it's actually a separate roof structure 1ft lower than the part of the house it's connected to, so the roof joists only cover the porch and are not part of the main roof. Even without an engineering report, I'm not confident in the structural strength of this thing, compared to a band joist.

- OUTER BEAM HEIGHT: The canale (roof drain) is 104" high. The cover would need to go under this, and about 4" clearance would be need for a drip flashing for the roof, so we have about 100" overall height to work with. City code requires 1/2:12 slope on the roof (metal panel). Subtract 2" for the roof, 5.5" for the rafter, and 7.5" for the beam, so if the rafters bear that puts the bottom of the outer beam at about 6'-10".

So I am left with some decisions about which direction to go here. The main question is, 1) ledger, 2) free-standing, or 3) "hybrid" self-supporting with attachment?

1) If I go with a ledger design, there are questions about the structural ability of the header on the existing porch. This quesion has been brought up at least one contractor, as well as the city building permits office. I have considered checking into reinforcing the existing porch so that the header could handle a ledger with no issues.

2) I could go with a free-standing design (with 4 posts) but this would require diagonal bracing. With the bottom of the outer beam at about 7FT, the braces would come down to about 5ft which might be a safety hazard (not to mention esthetically not cool). I could consider routing the output from the canale over to the side and just building the patio cover roof above it. One oddity here is the the city requires an attachment to the house for anything built within 10ft of the house, but it doesn't have to be a structural attachment. So, I would have to attach it anyway, though the attachment can be minimal.

3) This leads me to my idea for a "Hybrid" design. This would be a "self-supporting", 4-post design, but also attached to a ledger for lateral stability (no vertical load). No diagonals would be used, but I would use heavy t-straps (like the Simpson 1616HTPC) at the beam-post connections to help with the lateral stability. I haven't seen any designs exactly like this, but I have seen references to attaching a self-supporting deck to the house for lateral stability (to avoid the diagonal braces at the beam near the house). This is currently my
favorite idea, but I haven't seen any pics of this so I'm wondering why it appears that nobody has done it this way.

So, do you have any thoughts, suggestions, ideas, etc?
 
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Old 08-16-15, 04:31 PM
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Just to clarify, is the plan to cover the existing concrete patio that's seen in the pic? Either way, why wouldn't a canvas type awning be used instead? A former neighbor of mine installed something like that. He was extremely happy with it. There is no reason to attach a ledger or use 4x4 posts.
 
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Old 08-16-15, 05:30 PM
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No, I will be putting in a new slab for the new covered part. Thanks for the suggestion on the canvas cover, I'll think about that.
 
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