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Afternoon, folks. I have a deck that I am re-decking. Easy job, until I found that all of the footers were rotted out. The deck is bolted to the house on two sides, and the remainder of the deck is supported by 4x4 posts in concrete footers. The deck varies by between 4" and 12" off the ground, so getting new footers under the beams is not an option. I've had several thoughts:

1. Somehow remove the rotted posts from the concrete footings, fill the void with concrete and anchor a post base in there. Jack up the deck, insert new post, and then lower deck back down.

Problems: Not all posts are fully rotted and removing the remaining 4x4 has 
been difficult. I have almost no room to work under the deck due to it being 
just a few inches to a foot off the ground, so burning or pulling them out, 
even if possible, is not an option. I don't think that I can do this.

2. See "OFFSET1." Dig a new hole, drop in concrete tube and fill to 2" above grade, set post base, attach post, and connect to the beam from the side using carriage bolts.

Problems: I don't think I can get the auger close enough to the beam to be 
close enough for this to work. Not enough room to get the auger under the 
beam.

3. See "OFFSET2." Dig a new hole as close as I can to the current beam. Drop in concrete tube and fill to 2" above grade, set post base, attach post, sandwich in additional 1x12 to take up remaining distance btween post and existing 1x12 beam, and connect to the beams from the side using carriage bolts.

Problems: Does this put too much strain on the post base?

4. Demolish deck and start over.

Problems: Hell. No. 

So that's where I am at the moment. OFFSET2 seems like the only viable option. But I'm concerned about the stress on the post. Maybe if I stagger the offset posts on alternating sides of the beams the stress will be dissipated? What are your thoughts?

Three Optional Cofigurations

Deck

  • How big is the deck?, how many posts?, are they set in concrete like the "old" image?, Are the joists assembled with screws so you can dis- assemble them so you can have room to do the job right? Are the ledger board bolted to the house so you can unbolt them and jack the the assembly up to give you room to work? Can you post photos? Have you tried cutting the post off flush at the top of the footer? – Alaska Man May 12 '18 at 17:05
  • The deck is about 240 ft sq. I added an image in the original post. There are six posts, with their approximate location noted in the image as red squares. Yes, they are all set in concrete and below grade. The yellow rectangles identify the ledger boards. Yes, they are bolted to the house, but the deck itself is assembled with nails and cannot be disassembled easily. Lastly, yes, I can cut the posts flush, which I plan to do once the deck is supported in another manner. But jacking the frame up wouldn't help. I'd need to move the frame laterally as well so that I could get under the joists. – JD_HART May 12 '18 at 17:37
  • Jacking the frame up would help, ( you have to raise it slightly anyway to get the new posts in ). You do not necessarily need to move it laterally, you just need a little working room. Perhaps have a aluminum plate made to cap the concrete and provide a base for the new post to sit on. – Alaska Man May 12 '18 at 18:01
  • To get the new posts in, I'd have to dig a new hole. To do that, I need to move the desk out of the way. Now, if I were to cap the base and reuse it, you are correct in that I'd have to jack it up. But the old footings are really more concrete blobs than footings, and I'd have nothing level on which to mount a plate. Though, now that you mention it, I could drill out some holes and make an adjustable steel base using lag bolts... – JD_HART May 12 '18 at 18:28
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You can dig out the old footing where accessible even if means digging an "offset hole" to get it out. place a sonotube back in the hole, 6" above the bottom and fill the tube either 2" above grade for a short post or mount the clip to the deck after the old post is removed and run the concrete up to the clip. Place a wood form in the bottom of the hole if the offset is too much.

To get access to the other holes, remove 4 to 6 decking boards the get access from above, and do more of the same there.

None of it is going to be easy, but it is possible without tearing out the whole deck

  • Thanks, Jack! I may have to do that. Another idea: what if I cut the old post flush, put a sonotube over the existing footer to serve as a form, and create a nce, level pad that uses the old footing as a base. Then I can bolt something like this link into the new pad and, finally. insert and anchor the new post? – JD_HART May 12 '18 at 19:39
  • Typically, if you are going to add concrete on top of existing concrete, you need to join the 2 together. Usually this is done by drilling the old concrete and setting rebar with epoxy in the drilled holes then capping the old concrete off with new. I would not go with that clip you linked to, it still allows the post to come in contact with the concrete and with that moisture at the end grain. Something like this, amazon.com/Simpson-Strong-PBS44A-12-Gauge-Standoff/dp/… – Jack May 12 '18 at 23:42
  • So, nobody’s into me cantilevered post idea? – JD_HART May 13 '18 at 23:53
  • Not a big fan of "side loading" the post. It stresses the connection at the footing. If the post could be notched a bit to let the beam get under it a little would lessen the shear on the connections. I was hoping @Lee Sam would ring in on this.... – Jack May 14 '18 at 15:25
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found these on my local craigslist. If you can cut the post off and grind the top of the cement flatish you can secure something like this with anchors. I would put some kind of metal spacer in the bottom and drill some weep holes so water would not sit on the bottom of the post.

enter image description here

  • Fantastic. I found something similar, but in two pieces here. That would allow me to slide a new post in. I think I'll do pretty much what you and Jack have suggested, but I'll dig about 12" down around the current footer, pressure wash all of the crud off of the footer, and then pour 12" of new pad on top of the current footer. Then I'll use those braced I linked to, slide a new post in, and call it a day. Or, five days, more likely. – JD_HART May 12 '18 at 20:42
  • you may want to research how well new concrete bonds to old concrete and ways to best accomplish that. Re-bar or re-rod would be a good idea. Also prevent water for standing at the base of the post is most important. – Alaska Man May 12 '18 at 20:59

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