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Guidance needed for deck support posts

9K views 4 replies 5 participants last post by  Gary in WA 
#1 ·
I am hoping someone can help answer some questions regarding deck support posts and some other deck questions. Sorry this is a bit long winded.

I have an existing 14x14 deck that is at least 15-20 years old. The decking, railing were in bad shape when we moved in 13 years ago. I have nursed it along but am now replacing decking and railing with plastic decking.
In addition, I plan to enlarge the deck to 14x20 (using 20' long boards for the decking).
Also, whomeverbuilt it, did a bad job. For example, the beams are only nailed into the posts, the joists are only toenailed into the beams, the ledger board is bolted to the house bond board but only at every 32", the stairs are a complete structural accident waiting to happen, not a single screw was used in the entire deck, everything is nailed together, other issues too numerous to say all. Why did I not fix them? I did not notice until undertaking this project. I will fix them now with this expansion project.

First Problem: When I tore out the stairs, the 4x4 posts at the bottom of the stairs had some significant rot. The posts were "surrounded" by concrete at ground level, which had pulled away from the posts allowing water to get in. An inspection of the support posts for the deck show the same pulling away of the cement. Feeling down with a finger, I do feel some rot in the support posts. Not sure how much, maybe 1/4" that I can feel. DO THESE NEED TO BE REPLACED? If so, how do I do this? My first thought was just to keep the existing posts in place, but then to add new additional ones. The problem with this is how to dig the holes since the existing deck is cantilevered over the support posts/beams. Would it be easier to remove the existing and put new ones in the same location? If so, how?

Next problem, when I took the stairs apart, the deck can now "move", ie if I shake it in a direction parallel to the joists, it does move. I don't think that this is a big issue, but I plan to add more bolts through the ledger into the house, I plan to use joist hangers at the beam intersection etc., I plan to use lag bolts to better secure beam to posts. Sound good?

Thank you for any help anyone can offer
 
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#2 ·
I by no strech of imagination am a deck expert (as I too have posted questions here), but sounds like if it shakes, if it is "rotten a little" and you tore it down and it is 15+ years old....start OVER from scratch. Sorry. makes the most sense and safer than adding bolts! Bolts on rotten wood do not hold anything by rotten wood.

good luck,
adam
 
#4 ·
I agree and I have built plenty of decks... Pull the whole lot down and re-use what good timber you can.

I am not a fan of concreting timber posts into the ground, as over time these will rot and the natural expansion and contraction of timber vs concrete is vastly different, thus moisture will ingress and rot the timber.

The best solution if your ground is rock, sand, gravel or soil is to concrete a stainless (or galvanised) steel stirrup into the concrete and extening our if the ground to be bolted attached to your timber joists or posts, depending on your construction.

Alternatively, concrete and brick piers under the deck structure with a stainless bolt extending from the concrete footing, through the brickwork and bolted to the timber deck structure.

Then build your timber frame and deck...

Good luck with it..
 
#5 ·
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