Hello All,
I am adding 6 new footings in my 20″ crawl space (more like 14″ under the girders), each 20″ square and 12″ deep. I don’t think digging these out will be too terrible, but how can I do a good job of soil compaction under there? Bang a brick on the ground?
My plan was to open up the subfloor and use a jumping jack. But I’m trying not to open up my floor for at least 2 of them because that will take out my kitchen and shower, and it would be nice to stay in the house until most of the framing is done. After that, we’re gutting the entire place anyway.
Should I install jacks instead of 4x posts to compensate later for settling?
Please let me know if you have any suggestions, especially from any of you who do crawl space repairs!
Thanks!
-Aaron
Replies
Aaron,
What are you trying to hold up?
If undisturbed soil (not backfilled) in that crawl, you could feasibly form your footings at grade.
Thanks for the reply! I'll be holding up the roof and ceiling with these. Specifically, they will be supporting beams for a skylight and a tray ceiling. We are removing walls and doing some serious reconfiguring of the house. I have to go 12" below pad grade, per engineering. I'm in California so lots of seismic activity and engineering.
I don't think the crawl space was backfilled, but it was dug out 70 years ago. Not sure if it was compacted then. There are currently concrete blocks on/above pad grade for the existing pier and beam structure.
Speaking as a home owner who DIY'd a full height foundation and basement under my house, I would suggest that since you are gutting the house anyway you should demo the floor and joists in the areas for the all post footings. Not doing so drastically extends the amount of time you spend on the footings. Working under 20" clearance is frustrating and difficult, avoid it if you can. If the soil is loose fill you will probably have to dig deeper than 12" to get sufficient compaction (remove the loose soil and then compact in 1-2" layers to a 12" footing depth. If the soil is hard pan or with large rocks, digging may require a pick or jack hammer. At the very least try and find out what the soil is like under the house before you decide on your method of attack. I had 2-3' of loose soil under my house and then extremely hard compacted glacial till under that. The areas that I had ~24" clearance where very difficult to excavate, and I had a 4'-5' deep crawl space to start digging from.
That said, for some of the temporary support posts I had to place under main girder, I used a 10 lb sledge with a short handle to compact the soil in layers, and saw no settling over the course of about a year.