I'm hoping there are some fellow forum members, who are more learned than myself with regards to outdoor structure design/engineering/building, that are willing to provide some input on a patio cover I'd like to build for my home.

You'll have to pardon the kiddie art work posted below. I don't have access to a CAD program, so this was the best I could throw together on MS paint.



The patio space is  7' x 14' with an existing concrete slab. See Fig. A. The reason for the "U" shape is that the notch on the upper left is a raised step for the patio door/entry. The notch on the right is a slab level space with a window looking out onto the patio area. The space in between the notches is the fireplace.

I think I've got the basic design down, but I have some concerns about the overall load capabilites of the structure. I live in the North Texas region (DFW Metroplex), so I do need to consider snow/ice load. (mostly ice, heh) The wood material will be rough redwood cedar.The roofing will be corrugated metal. Hardware will be galvanized bolts, and stainless screws.

On Fig. A I've noted my current planned placement of the primary 6x6 posts. They will be anchored to the concrete slab using Samson StrongTie ABU66's. The slab itself appears to be 5" thick based upon digging investigation along the edge. The posts furthest from the house will be ~ 8ft tall. The posts nearest the house will be ~ 10ft tall to accommodate roofing eaves. I know this will create a steeper pitch than necessary, but it's the only way to get the cover to fit in the space without attaching it to the home. Yes, I know that is probably a better option, but there are reasons why I'm not taking that path.

Fig. B and Fig. C give you an idea of the dimensions of the cover itself. Fig. D shows how I intend on attaching the crossbeams to the posts. The crossbeams will be 2x8's. The rafters will be 2x6's, and the slats will be 2x4's. The corrugated roofing will then attach to the slats. I also plan on installing 2x6 braces to prevent "racking" of the frame.

My questions are:

1. Based upon the current design, is there a need for center 6x6 posts, given the 12.5' (on center) span between the outside posts?
2. Does the use of braces mitigate the need to for center posts?
3. How far out should the braces extend from the 6x6 posts? My guess would be "whatever it takes to create a right triangle", correct?
4. Considering the small space, should any of the material dimensions be downsized/is there too much overkill in the sizing being used? I.E. Would 4x4's and 2x6's suffice to replace the 6x6's and 2x8's?
5. Any other concerns that I'm not considering, or addressing?

As always, any and all input is greatly appreciated.  

ETA: Spelling

My inputs, based on personal preference not engineering calculations:

Get rid of the diagonal braces.  Use the really heavy Simpson Strong-Tie T's every place a cross beam passes over a post.  In fact, use joist hangers and steel reinforcements at every joint/overlap.

The diagonals will not reduce the unsupported span by enough to eliminate the sagging.

Stainless screws don't rust but they are very soft.  What were you planning to use them for?

Use hot-dipped galvanized hardware everywhere possible.  Zinc-plated sucks and is not a good substitute for hot-dipped.

You will want a center post.  14' is too long and you will get some amount of sag.

Use 2X8 roof rafters or you will get sag.


Consider anchoring/tying the roof into the house.  If you don't how will you stop a wind storm from causing the roof to bang into the exterior wall of the house?  The diagonal braces could help prevent any movement toward the house but you do not show any in your sketch.


If I am wrong on any of this, the pros will be along soon enough and will straighten me out.

I just did a patio cover at my house. Mine is 16'x16' I used LVL beams. No need for center supports or bracing. Look into it. The cost of the beams
wasn't much more than if I were to have added another post in the middle, and the amount of work saved was tremendous. Don't know if that helps
but it worked great for me. Here is my thread. maybe it will help you with some ideas.

patio cover thread

I was originally looking at using the StrongTie solutions for most of the build, but wasn't certain if that would be the best direction.
I have no objection with using completely hot-dip galv hardware. I was just using stainless because I know that certain metal coatings (Zinc specifically) don't play well with the oils/resins in wood, which can lead to fatigue and failure over time.
I figured the center post would be necessary, but wanted to make sure before factoring them in to the material costs.
I'll change the rafters to 2x8, and hang them with the StrongTie joist hangers. I was thinking about notching them to connect to the cross beams, but the joist hangers will be a stronger/better solution.

I know attaching to the house via ledger board would be the most secure answer, but there's an issue I'm having to work around that's preventing me from going with that solution. Specifically, property setback. My city notes a 7 ft setback. If you'll notice, the patio is exactly 7 ft wide. The edge furthest from the house is actually my 8 ft tall cedar fence line. There's a 4ft wide breezeway on the other side, and them my neighbors home. My property actually sits on a 2 tiered rising above the street level. (about 8 - 10 feet higher) You can't see this part of the backyard/sideyard from the street, so a casual city inspector drive by will never notice the patio cover. But if/when we do sell the house I'll have to tear it down. No code inspector will let its existence fly, no matter how well built. I can't justify the installing the ledger on the house, and then having to tear it down/out at some point in the future. I would rather build an over-engineered free standing unit that can be disassembled with less impact to the physical home structure. (Plus no permit submitted to draw attention.) It won't make the area completely weather proof, but at this point something providing shade is better than nothing at all.

I can certainly add diagonal braces to the short ends to help prevent the cover's movement toward the house. My only issue is that is also the walkway to the rest of the yard. I'll need to make sure to provide enough space between the braces to comfortably pass through.



LVL beams? I've never seen/heard of those. I'll look into that option as well.

Thanks for the thread linkage. Lots of good info. Based upon that reading if I don't go the LVL route, I'll need to reconsider the front joist beam sizing, which would tie in (ha pun! ) with Trollslayer's suggesting with using the StongTie T connectors.

ETA:

Something more along these lines?

Just remember normal lumber with a span of (x), and weight of (X) on top of it will eventually bow to the weight if it isn't sized right.

With an LVL you won't need the center post, and it will more than support the span. and if you notch out the 6x6 you won't need any hardware to attach the beam to the posts.

I often forget regional variations.  Out here, you Strong-Tie everything because of the seismic activity.  

EARTHQUAKE!    

I think I'd still use the steel T's.  You never want your roof to fall off the posts.  The closer it is to the house, the less you can afford to have it happen.  Do you get hurricanes or tornados?

No nearby fracking yet, so no earthquakes.

Hurricanes, No.

Tornados, Yes.

My house was hit by a verified F0 tornado a couple of years ago. Fortunately, no major damage beyond having to put new shingles on the roof. The neighborhood trees didn't fair as well.

Stainless beats even hot dip galvanize.
Diagonal braces are for racking resistance.
They produce no change in span.

Only in corrosion resistance in strength, they suck.

The alloy they use for most stainless steel screws is so soft, I lose about 10-25% when the driver bit strips the drive socket, bends the shank during driving and twists the head off as screws goes in.

I love them for fences where the wood is soft and thin.

Very similar to one I did a few years ago. A 14'x30' patio pergola. 6x6 posts with 2x6 beams on 16" centers with 2x4 boards going perpendicular to the 2x6's every 6 inches w/ a simpson twist tie on every joint. That was thousands of nails.