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View Full Version : How to build foundation under current home?



gijoe985
06-11-2010, 05:02 PM
Hey all,

There is a home that a friend and I were looking at as an investment. The main problem is that it has no foundation and is in need of one. It is a multi family unit and there are tenants currently living inside. We'd like to build a foundation without having to kick everyone out. There is currently only 6" of space under the house.

One idea that was proposed was to do the foundation section at a time and possibly use shotcrete. I have framed up and poured a foundation before, but have no shotcrete experience. My friend who suggested it is unsure if it'd work (and be accepted by the county) but he think it'd have some advantages.

Any thoughts/suggestions?

David Meiland
06-11-2010, 05:47 PM
The usual approach is to jack the house up above the final elevation you want, build forms and pour concrete, and then lower the house onto the foundation or pony walls. Or, jack the house up to final elevation, pour a foundation, and then frame the pony walls in one stick at a time. Or.... leave the house at the existing elevation, build forms right up to the existing framing, and pour, allowing yourself a way to get mud all the way to the top.

I don't think shotcrete is worth exploring (or at least I have never seen it used as a foundation) and I definitely would not put a foundation under a house that's only got 6" under it--that will make any further remodeling nearly impossible, such as replumbing, rewiring, insulating, etc. Better to get it at least 24" off grade.

S.Joisey
06-11-2010, 06:19 PM
You'll have to kick everyone out.

gijoe985
06-11-2010, 06:20 PM
I definitely would not put a foundation under a house that's only got 6" under it--that will make any further remodeling nearly impossible, such as replumbing, rewiring, insulating, etc. Better to get it at least 24" off grade.

Well, our problem is that the house is apparently not well supported with its current setup. (I'll say right now, I don't know a ton about this house, but I am just trying to do some research about foundation solutions if that is the route needed) From what I heard the house is sinking in the middle. So the lack of foundation is hurting.

I also believe the goal was to try to work on a foundation without jacking up the house.

And thanks a ton for the good info. All suggestions are welcome.

David Meiland
06-11-2010, 06:29 PM
If the house is worth anything then it makes sense to do a proper foundation. For better or worse I've done several of those retrofits. You probably need a concrete perimeter foundation with piers and girders within that. It is virtually impossible to do stuff like that without lifting the building, and once you are set up for the lift you can easily go high enough to make working conditions tolerable. I lifted my house 6' so we could stand upright while we worked.

Lavrans
06-11-2010, 08:02 PM
A project I looked at a while ago got around this problem by installing earth anchors to support the house while they dug the basement out and poured new foundation walls. Turned out the earth anchors met code to support the house without the foundation and they could have installed the earth anchors under the perimeter of the house instead of outside of it.

You could always just install spot footings and then infill foundation between. Problem with that and most ideas is what your insurance company is going to say about doing foundation work while people are living in the house. Spot footings would be pretty easy and might be enough by themselves anyway.

davenorthup
06-11-2010, 11:50 PM
You'll have to kick everyone out.

NO way - we do it all the time w/o kicking people out. It is inconvenient; but possible.

We just lowered this one down the other day.....

It was done like Dave mentioned.


You probably need a concrete perimeter foundation with piers and girders within that. It is virtually impossible to do stuff like that without lifting the building, and once you are set up for the lift you can easily go high enough to make working conditions tolerable. I lifted my house 6' so we could stand upright while we worked.

Talk to your local excavator or house mover. We seem to do it all the time up here with old rotten wood foundations.

This one we lifted about 4 inches, and it was already about 2' off the ground. Poured the footers and then the walls. From there we added a 16" framed wall above grade and added an 8' basement (section for a water tank) off a section of the house we demoed.

Then we lowered and attached the house to the new foundation.... Actually a simple process. A few years back we moved my own house over a 8' basement.

gijoe985
06-12-2010, 01:46 AM
All really great stuff guys, thanks so much. I'll be passing this all on.

gijoe985
06-12-2010, 11:00 PM
So I guess my next question would be, if the house is sagging do to lack of foundation/support, would there be another suitable solution to the problem that wasn't putting in a foundation? Something more practical? (I have not idea what that may be...)

davenorthup
06-12-2010, 11:22 PM
So I guess my next question would be, if the house is sagging do to lack of foundation/support, would there be another suitable solution to the problem that wasn't putting in a foundation? Something more practical? (I have not idea what that may be...)

I subscribe to Meiland's theory.


If the house is worth anything then it makes sense to do a proper foundation.
I do not know anything of the existing structure to determine if a 'work around' would be worth it.

dgbldr
06-13-2010, 03:38 PM
What is the house sitting on right now? Framing directly on the soil?

David Meiland
06-13-2010, 04:30 PM
Mine was on an assortment on fieldstones and cedar stumps. The stones were holding firm, the stumps were wilting. There is nothing quite like the sound of a house as you jack that sag out of the middle.

gijoe985
06-15-2010, 09:57 AM
Mine was on an assortment on fieldstones and cedar stumps. The stones were holding firm, the stumps were wilting. There is nothing quite like the sound of a house as you jack that sag out of the middle.

Ha... Stumps and field stones... Sounds like the San Juans... I'm over here in Ellensburg WA.

David Meiland
06-15-2010, 10:18 AM
House was built in the 1930s. Wood, nails, glass, possibly paint, bricks, some lousy mortar. You have to give farmers a lot of credit.

Tom Bainbridge
06-21-2010, 07:22 PM
dont even think the word "farmer"

with me around

communists, politicians and religous fanatics are better people

David Meiland
06-21-2010, 08:21 PM
No farmers, no food.... and some of the farmers I know are highly entertaining.

What's wrong with English farmers?