Ideas and suggestions for patio cover design


Old 05-10-19, 01:04 PM
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Location: Albuquerque NM
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Ideas and suggestions for patio cover design

I'm making plans for a patio cover.

As always (with a deck OR patio cover), the first question to be answered is, will this be attached or freestanding. In reality there are 3 basic designs - attached, freestanding, and non-ledger:

Attached: Uses ledger to bear both horizontal (lateral) and vertical (gravity) loads. Requires bracing unless the top surface is a rigid diaphragm, which is fairly easy to accomplish with a patio cover but may not be possible (or allowable) for a deck.

Freestanding: Not attached to the house for either horizontal and vertical loads. Requires bracing.

Non-ledger: Not attached to the house for vertical loads. Uses an attachment to the house for horizontal loads. Requires bracing unless the top surface is a rigid diaphragm, which is fairly easy to accomplish for a patio cover but may not be possible (or allowable) for a deck.

OK, with definitions in place, here's the situation. An attached patio cover would be my preference, but the location is not great for doing a ledger. There's a porch header there, some of which would need to be used for the ledger attachment. It's possible to do it, but might require an engineer's approval which I'd like to avoid due to the cost. Even if I could get such approval, I'm not sure I like the idea. OK, on to the freestanding design. Due to the style I prefer and the height of the roof, having a lot of bracing is aesthetically unacceptable. OK, so that leaves the non-ledger. This would have an additional pair of posts near the house, maybe 2 feet out. Putting a foundation down to our frost line at this position is not a problem. However, due to the style and green timbers I'm using, there will be considerable shrinkage, meaning
the height of the roof will drop by maybe 1/2 to 1 inch. This is not a problem except for the attachment for the horizontal loads. This shrinkage will occur at the two beams, but not at the attachment, resulting in some downward load on the attachment. This is the problem.

Two solutions have come up:
1. Adjustable (screw-type) bases on the inner posts. This might work, but due to the design would be difficult to implement.
2. Custom slotted steel attachment brackets for the horizontal load. This would work but I haven't seen an examples of this, and since I'm a DIYer and I like to copy known, industry-acceptable designs. It's kind of like the deflection clips they use in steel frame construction though, so it's nothing new.

I've considered changing the design to move the inner pair of posts up to the house so I could attach the house to the inner beam, but I'd have concerns with putting the new footing so close to the house. I've seen some people say this is OK, but some people say it's not OK, so I don't know what to believe.

And one more idea. I've considered increasing the size of the ledger so it actually becomes a beam. Then it's bolted to the house only at the ends (clear of the existing porch header) and does not transfer any vertical load to the porch header. I would then use a "half post" under the ends of this beam, bolted to the house.

With this design the vertical load is transferred to the house via the bolts at the end of the beam and the half-posts only, with no load on the porch header. All vertical load if this beam bears on the house only, so no additional footings are needed next to the house. Visualize a beam with two posts, right up against the

house. I think this would work. I've seen this sort of design used with timber structures that are built right next to a stone building, though in that case I think they do add a footing next to the existing building

foundation. In this case the additional footing isn't needed because the dead+live load is only about 600-700 lbs on each end of the beam.

I've attached a picture so you can see what I am talking about.

Suggestions, comments, questions?
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