My wife has convinced me to put a pergola over our concrete patio and because it's not a standard size, and because I consider myself handy, I was going to build it myself.

Some of you all have engineering and construction backgrounds and I clearly don't. I trust you all to tell me I am completely crazy or a rational DIYer.

Here are my specs:

4" concrete pad up against the house and 14' x 17'8". Eaves of the house are 9' off the concrete and roughly 2'6" wide. Attaching 6"x6" posts with Simpson Strongtie ABU66Z giving 6" birth from the edges of the pad and the eaves leaves the posts about 11'x16'8". Are those spans too wide? I had planned on putting some knee braces on long sides.

So 6x6 posts at 10' tall, sandwhiched by 2x10s on the longs (parallel to house) and 4x4 knee braces. Cantilever of 18" means I need four 2x10s at 20' for the girders, not flush but raised 2" above the top of the posts. This and the raised 1.5" base support would give me a clearance over the gutters of 5.5". Is that enough?

Then placing 2x8s rafters on 16" centers for a total of 15 would run perpendicular to the house. Do these need to have as long of cantilevers? I would rather not have to notch ever single rafter, can I toe screw them in and if I do is that one screw per girder alternating each side of rafter (4 total screws) or both sides of the rafter at each girder (8 total screws)?

Lastly some rafter stays. Are they needed and what size? 2x2 or 2x4? Same length as girders with 18" cantilevers?

All of this to be done with PT pine not from a box store. I should leave them out a month to dry before staining them, correct? Is there a suggested diameter for carriage bolts? If I countersink the head and nut then I am looking at 8" bolts on the girders and possibly the knees as well?

If I want an outdoor fan should I plan for an even number of rafters to center the fan? Would you put knees on the short sides as well? No there will never be a roof. Not attaching it to my 1950's fascia. Are my rafters to far apart from each other or need to be 2x10s like the girders?

What are your thoughts?

Up front, I didn't read or put much thought into your post. But when I built my pergola, I just found a design and size on homedepot.com. On each design's page, there is a section that has installation guides and instructions. From there, I got a material list and built it myself using the instructions.

Really? 150+ views and no one pulls a Randy Cody?

FincAg said:

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My wife has convinced me to put a pergola over our concrete patio and because it's not a standard size, and because I consider myself handy, I was going to build it myself.

Some of you all have engineering and construction backgrounds and I clearly don't. I trust you all to tell me I am completely crazy or a rational DIYer.

Here are my specs:

4" concrete pad up against the house and 14' x 17'8". Eaves of the house are 9' off the concrete and roughly 2'6" wide. Attaching 6"x6" posts with Simpson Strongtie ABU66Z giving 6" birth from the edges of the pad and the eaves leaves the posts about 11'x16'8". Are those spans too wide? I had planned on putting some knee braces on long sides.

- No span is too wide if you use big enough beams.
- You need knee braces in 3 directions since those post bases don't provide much resistance to pivoting. Although most people leave out the one parallel to the ground that keeps the top from twisting since it doesn't look very good, or they notch the beams to achieve the same result.

So 6x6 posts at 10' tall, sandwhiched by 2x10s on the longs (parallel to house) and 4x4 knee braces. Cantilever of 18" means I need four 2x10s at 20' for the girders, not flush but raised 2" above the top of the posts. This and the raised 1.5" base support would give me a clearance over the gutters of 5.5". Is that enough?

- Yes, make sure they clear the roof pitch though and add a gutter guard since cleaning them out won't be much fun with 5.5" of clearance.

Then placing 2x8s rafters on 16" centers for a total of 15 would run perpendicular to the house. Do these need to have as long of cantilevers?

- For aesthetic reasons, yes. For all other reasons, no.

I would rather not have to notch ever single rafter, can I toe screw them in and if I do is that one screw per girder alternating each side of rafter (4 total screws) or both sides of the rafter at each girder (8 total screws)?

- You can. It will be less stable and more susceptible to warping and cracking at the screw points. I also wouldn't walk on one because the boards can easily rotate and the screws can split the wood. Will also probably prevent you from adding a roof later when the Mrs. decides that what she ACTUALLY wanted was a roofed-porch in the hot Texas sun instead of the pretty pergola she saw in a magazine.

Lastly some rafter stays. Are they needed and what size? 2x2 or 2x4? Same length as girders with 18" cantilevers?

Required if you toe-screw the top, and I'd want them anyway since the posts won't be sunk 3' into the ground and able to resist lateral loads. 2x2 WOOD is strong enough to work, but the fasteners through something that small would make for a weak point that could easily crack. I'd recommend 4x4s like the other braces strictly for aesthetic reasons.

All of this to be done with PT pine not from a box store. I should leave them out a month to dry before staining them, correct?

I stained some very wet ones because of a nagging girlfriend and they did fine years later as far as the stain goes. What WASN'T fine was the warping. If you can get them in the garage for a week or two out of the rain to make sure they're not going to start warping badly, that would be a great idea.

Is there a suggested diameter for carriage bolts? If I countersink the head and nut then I am looking at 8" bolts on the girders and possibly the knees as well?

Hot Dipped Galvanized are absolutely required. Plain galvanized won't cut it.
If you countersink the head, remember that the amount of wood you took out (1/2" for example) takes your 2x10 from 1.75"wide to 1.25" wide. Probably not a problem until you want to put a roof on it.

Knee bolt diameters don't have to be big since they're only keeping things from pulling apart. Girders have to actually support the weight of the beam so they should either be bigger or use more of them. Got the multibox from lowes, and the big bolts hold up a whole lot of weight with two bolts and it's fine even when drunk idiot friends start swinging from the pergola like it's monkey bars.

If I want an outdoor fan should I plan for an even number of rafters to center the fan?

Depends if you want to mount the fan to a rafter or between rafters. You can do both.

Would you put knees on the short sides as well?

Like the cantilevered side? No structural purpose, so only if you like the way it looks.

No there will never be a roof.

Others have said that before...

Not attaching it to my 1950's fascia. Are my rafters to far apart from each other or need to be 2x10s like the girders?

2x8s are fine unless you will be doing a lot of walking up there (or adding a roof )

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"You need knee braces in 3 directions since those post bases don't provide much resistance to pivoting. Although most people leave out the one parallel to the ground that keeps the top from twisting since it doesn't look very good, or they notch the beams to achieve the same result."

Tell me more about these three directions. I was considering knees on the long span and short spans, 16 ft and 11 ft respectively. Where is the horizontal?

He means the red knee brace in this image:

Ah, got it. How would you fashion that if you only have girders on the 16 ft span? Looks like I need girders on all four sides.

When you notch the rafters, 1/3 or a 1/4 through a 2x8?

Thank you all for the advice!