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-   -   Pergola Questions (http://www.diychatroom.com/f19/pergola-questions-25481/)

LDO 08-19-2008 09:38 PM

Pergola Questions
 
I would like to build a free standing pergola over the slab in our backyard. The dimensions of the slab are 20ft wide by 12ft deep.

I don't think it would be structuraly sound to try and span 20 ft between just two front posts and I would prefer to split the distance over 4 posts rather than using 3 and having one in the middle but how do I attach the posts closest to the house to the existing slab?

For the other posts, I was planning on burrying them 3ft in cement. I live in PCola so I gotta make this thing as strong as possible. Any help is greatly appreciated. Feel free to be as specific as you can with regards to recommended materials.

Thanks,

LDO

Termite 08-19-2008 10:02 PM

I think your best bet is to give the pergola a solid footing for each post. You could rent a concrete saw and easily cut out a small square for each footing. Simpson post bases could be imbedded in the concrete piers, which would keep it from blowing away.

The actual design of the pergola will determine how tough it is to make it a solid structure. A few posts opposing each other in two planes will be more sturdy than all the posts in one plane.

LDO 08-20-2008 08:22 AM

Quote:

Originally Posted by thekctermite (Post 150183)
I think your best bet is to give the pergola a solid footing for each post. You could rent a concrete saw and easily cut out a small square for each footing. Simpson post bases could be imbedded in the concrete piers, which would keep it from blowing away.

The actual design of the pergola will determine how tough it is to make it a solid structure. A few posts opposing each other in two planes will be more sturdy than all the posts in one plane.


Thanks,
any more info on how to make proper footings? Last pergola I built, I just dug a 3 foot hole and used the ready mix and leveled the posts.


Thanks.

agrace 08-20-2008 09:49 AM

Check with the county regs. We put a larger pergola up in Mich. for every 2ft above ground we had to go 1 ft under. 8ft above and 4 ft buried. They came out and measured depth before we put posts in. We used tight pack pea gravel instead of concrete so the PTL last even longer but your ground is probably sandy where ours is clay. Used 6x6 for in ground and 2 x10 for rafters, its been up since 96 and has double swings on it plus a Trumpet vine has fully covered it with flower canopy now. Still standing strong! Good Luck with yours.
agrace

LDO 08-20-2008 12:19 PM

Is a 20 foot span too long between 2 posts? Who sells lumber that long? I've only seen up to 16 foot lengths at Lowes.:wink:

agrace 08-20-2008 12:47 PM

What are you using the pergola for?
 
If your use is to park a car you need 10ft of width for each car. This means you'll need a center beams. In other words 6 boards for support and then cross members for the top.
If you just want a shade area or for swings 16 ft is plenty. I have 2 swings on that length. I'll try to post a pic for you if I get a chance.

LDO 08-20-2008 02:49 PM

1 Attachment(s)
Quote:

Originally Posted by agrace (Post 150338)
If your use is to park a car you need 10ft of width for each car. This means you'll need a center beams. In other words 6 boards for support and then cross members for the top.
If you just want a shade area or for swings 16 ft is plenty. I have 2 swings on that length. I'll try to post a pic for you if I get a chance.

Thanks agrace. I'm using the pergola for shade over an existing slab that measures 12 foot deep by 20 foot wide.

Here's my plan.
I was going to burry the (4) 6x6 posts around the outside of the slab about 3.5 ft using about 6 inches of gravel for draining. I'll probably wrap or melt some roofing material around the lower (buried) part of the posts.

I found a place locally that carries 2x12s in 24 foot lengths (to span the width of the slab). Pricey, but they are available and will deliver for free. I was planning on sandwhiching two 2x12 beams (by notching the posts and using lag bolts) on the front and rear posts. Then running 2x6s or 2x8s perpendicular to the beams and then 1x2s on top of all that.

Here's one I built a few years ago when I was stationed in South Carolina.

If anyone else has any advice or recommendations, I'm all ears!

Thanks,
LDO


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