Jacking this Old Leaning House
Jacking this Old Leaning House
(OP)
Though originally a geological engineer, I now practice in the environmental field, and as such, my foundation and soils engineering knowledge is now somewhat faded... so in the hopes of getting some sage advice, here is my foundation rehabilititation issue:
We purchased (at a great price!) a post-war 24'X30' bungalow with a lean to it -- 6" lower along one side. We have dug a few test pits and found that the problem appears to be differential settling due to: 1) no footings at base of perimeter wall (crawlspace, no basement), and 2) about 2/3 of the perimeter wall base sitting on a clayey/peaty lens, versus a fine dry sandy strata under the 1/3 that has settled minimally.
We are considering, given that there is no footing, of jacking both house and the concrete perimeter wall up as a unit. We are looking at jack points every 6-8', strategically under supporting beams and existing cracks in the wall. The plan is to dig down from the outside of the house at the jack points, pre-pour jack pads, raise the wall to the desired level, then pour footings under the remainder of the wall.
I have two questions for you experts:
1) If anyone has experience with this particular strategy of jacking house and wall as a unit, please comment on your success or failure, give any advice for strategies.
2) Given the clay soil conditions, a one-story woodframe bungalow with asphalt shingle roof, and the settlement history of 6", what are the opinions out there of a desirable footing design? We do not intend to put a second story on the structure, and just want to find a cost-effective solution to this problem. I can do more detailed sizing calculations myself, but really want more your ideas of options we could consider.
Thanks very much!
We purchased (at a great price!) a post-war 24'X30' bungalow with a lean to it -- 6" lower along one side. We have dug a few test pits and found that the problem appears to be differential settling due to: 1) no footings at base of perimeter wall (crawlspace, no basement), and 2) about 2/3 of the perimeter wall base sitting on a clayey/peaty lens, versus a fine dry sandy strata under the 1/3 that has settled minimally.
We are considering, given that there is no footing, of jacking both house and the concrete perimeter wall up as a unit. We are looking at jack points every 6-8', strategically under supporting beams and existing cracks in the wall. The plan is to dig down from the outside of the house at the jack points, pre-pour jack pads, raise the wall to the desired level, then pour footings under the remainder of the wall.
I have two questions for you experts:
1) If anyone has experience with this particular strategy of jacking house and wall as a unit, please comment on your success or failure, give any advice for strategies.
2) Given the clay soil conditions, a one-story woodframe bungalow with asphalt shingle roof, and the settlement history of 6", what are the opinions out there of a desirable footing design? We do not intend to put a second story on the structure, and just want to find a cost-effective solution to this problem. I can do more detailed sizing calculations myself, but really want more your ideas of options we could consider.
Thanks very much!





RE: Jacking this Old Leaning House
RE: Jacking this Old Leaning House
RE: Jacking this Old Leaning House
Another option is to hire a house mover to pick up and support the house, move it a few feet so that you can get good access to the foundation area, and then put in whatever foundation system you like. One easy system that will work for this based on the soil conditions you have described is an augered concrete pile.
Good luck.
RE: Jacking this Old Leaning House
Thanks again! I will keep you all posted on progress.
RE: Jacking this Old Leaning House
If the "peaty layer" is the problem (you need to be sure) and if it is not very deep then underpinning with jack points as you have described would likely be an economical solution. If the problem is deeper or below the water table then screw piles become more economical. You should be sure that the peaty layer is the problem by comparing the amount of settlement vs thickness of the layer and by exploring below the peaty layer to confirm good ground to depth.
Depending the details of your particular case, a very cheap alternative might be to disconnect the plate of the house from the foundation wall and shim the settled portion level then reconnect the plate. This does not require that you lift the foundation wall. Depending on the soil conditions in your 'peaty layer' it might not prevent further settlement. We have used this approach where we have assessed further settlement as being small compared to the initial settlement. If decomposition of the peat is a question then the alternative leveling below the peat layer would be the best approach.
regards
RE: Jacking this Old Leaning House
Permalock is similar except instead of a cable, each cylinder has a treaded 3/4 inch rod cast in it. See the website below: http://www.jmgraphics.net/permalock/Perma_Lock/perma_lock.html
RE: Jacking this Old Leaning House
RE: Jacking this Old Leaning House
If your lot is too small, have the house moved off the lot, excavate out the foundation area, replace it with compacted fill, and put the house back.
RE: Jacking this Old Leaning House