Wanting to build a pergola on my deck


Old 03-17-14, 09:43 AM
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Wanting to build a pergola on my deck

I am looking for advise on building a cedar pergola on top of my existing deck. I have attached a deck load diagram from a calculator I found online detailing each zone of the deck's load. I am wanting to install a 9' X 10' X 8' pergola. I am wondering if the deck would be able to hold the pergola as it is, or if I should put another beam down the middle of the deck with 3 more posts underneath. The deck is 3 feet off the ground, and I do not want to cut through the deck to have the pergola posts reach the ground. Therefore, I would rather put another beam with support posts underneath. The 3 outer posts of the deck are on soil with cement footings. If I were to put another beam down the center of the deck, these footings would be on a cement slab. The entire area under the deck is a cement slab. The posts of the pergola would be 4X4, and they would match up and be anchored to the deck joist instead of being anchored to the deck surface boards. Any help or tips would be greatly appreciated.
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Last edited by bhale; 03-17-14 at 10:39 AM.
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Old 03-17-14, 08:16 PM
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The unit loads in your attached sketch don't look right--having 1606 PSF, applied over a large area, will overstress most 4 x 4 columns. How deep is your frost line? I would never support anything carried by tall columns on a "cement slab," when a proper concrete footing below frost line is required by most codes. And if you're penetrating the deck planks to attach columns to the joists underneath, why not just go with full-height columns, through the deck and down to footings at ground level? Maybe your AHJ should be brought into the picture early, since they'll be issuing the building permit.

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