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Building Homes or Extensions/Post Attachment Requirements

Expert: Dave Johnson - 9/28/2009

Question

I am installing a flat roof with a 3" slope in 16' over an existing 2x8 12oc pressure treated deck. The deck is attached to a ledger board that is attached to my house by a number of large lag bolts and on the back the joists rest on a 6x8" 10' long rough cedar beam that in turn rests on 2 6x6" rough cedar posts that rest on top of 2 12" diameter concrete piers that are 36" in the ground. The beam cantilevers the posts 12" on each end. Joist hangers attach the floor joists at both end to 2x8" ledger board and rim joist. I will be installing 6x6" rough cedar posts approximately every 4' on the perimeter of the deck to hold up the 3" sloping roof and provide structure to attach the screening. I will also install railing since the deck is 6' feet above grade. My questions are 1- Do I need to double the treated rim joists to support the posts or can I add a 2x8" rough cedar on the outside that will rest partially on the protruding 6x8" beam? 2- Can I rest 6x6 rough cedar headers on top of the 6x6" rough cedar post that are less than 4' apart? 3- Do the posts need to extend down the joists and be notched and bolted to the rim joists or can they just be nailed on top?

Answer
HI Jerry,

1) I think that if all the rest is going to be cedar, you may as well use it there. ( better looking than p.t.)
2) Yes, but let me say too, that I'm thinking 4"x4" would do just as well for this project.
3)Not necessary to penetrate the floor, but make sure there is blocking under the posts if they aren't fully supported by joists. You can also screw up through the floor/franing to attach the posts and not have fasteners showing above.

Best of luck, and mail me again if you need more..

Dave