Topic: sinking front porch.
My house, built 10 years ago, has a front porch with a balcony above it. The footprint of the porch is approx. 4’x8′, the long side against the house. The framing for the porch is attached to the house wall on one side, and supported by a post on a concrete footing on each of the two outer corners, about 4′ away from the house. The porch is sinking toward the supporting posts. I dug up to the top of the footings and found them to be about 18″ below grade. I assume that when the area was excavated for the concrete foundation of the house that the area under the porch was also excavated, and then backfilled, and that the porch footings were then poured on improperly compacted soil, resulting in the problem of the sinking footings. I’m concerned that these footing will keep on sinking and am reluctant to rely on them when we jack up the porch. Any ideas on how to get adequate footings in place without tearing out the whole structure?
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Replies
i think you got it figured right
jack & shore, then remove the old footings .... dig deeper until
you get to undisturbed earth , then repour your footings and install your permanent supports
Thanks.....How do I determine where undisturbed soil is? Any possibility of using something like small scale "piles" with a grade beam poured on top of them?
Save yourself from a whole lot of work. Just replace the wood post, with a longer one, on top of the OLD footing.
This is based on the theory that the existing footing has settled 90% of what it is gonna do. If you changed the post 4 times, would take a lot less time digging and pouring concrete.
Many times when someone re-dug an old footing, they could never dig deep enough (past the trash).
that was my first thought also... BUT
he says these footings are only 18" down... so they are still in the frost zonetime to get better footingsMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
I was thinking along similiar lines............like creating a 10' x 1.5' footing 10'' thick. Will give you LOTS more bearing than what you describe you have.
Or 2 2'x2' footing with sonotube piers on top.
At 4' away from your foundation you are likely in or on the edge of the "overdig" fromwhen the original footings for the house were dug.
As such it is very likely that you may have to dig down to the same elevation as the bottom of your house footings.
Being so close to the original footings it would have been a cake walk for the builder to pour a couple of 2x2 pads while he was there.
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." — Sherlock Holmes, 1896
I just spent the day retrofitting footings under a porch that I plan to close in. Not a lot of fun, but here's the basic drill:
1. Temporarily support the roof so the weight is no longer on the current footings. As part of this effort, lift the porch back to where you want it if it has moved. Lots of ways to do that - ask if you need help. You may have to cut the vertical posts loose from the old footings before lifting it.
2. Dig a large hole next to and under the existing footings. Looks like you're from NY - in MA the required depth is 4' - not sure about your climate but it's probably close to that. So the hole depth should be 4' below grade. This is not fun digging because you want to be below the existing footing. Plan to spend a lot of time on your belly.
3. Slip in sauna(sp) tubes. I used 12" diameter - might be overkill. You may have to trim the top of the tube to be able to slip it in around the existing footing (which you will incorporate into the new concrete pour. Make sure enough of the tube is underneath so that the entire post is on the new footing.
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4. Use a 2x4 or something to tamp the bottom of the hole (inside the tube ) so that the soil is firm.
5. Mix and pour the 'crete - I used ready mix 80lb bags - about 5-6 per hole.
6. Wait a couple days and let the weight back down on the new footings.
I was able to dig and pour one per day - did 3 of them.
Good luck!
Thanks for the detailed response....looks like some messy digging is going to be involved.
This happened to my place, but the porch stopped sinking after about 2 inches. It's been stable for two years now. I simply jacked up the posts and put in a 2" shim of wood between the footing and post.
Be advised that you may have to go a long way down before reaching truly undisturbed soil, depending on how they excavated. I'd try the shim approach first.
Scott.