What are my options for saving this building?

Question

I have a small building on my property that is about 15ft by 10ft. The building sits on a slope that runs downhill sort of at an angle from one front corner to the opposite back corner.

It sits on an odd foundation (at least odd in my experience). The front edge is sitting on a solid-looking concrete footer that is in the ground flush, while the back seems more or less unsupported. The sides of the building rest on some kind of concrete walls. I say "some kind" because it's sort of a chunky looking aggregate, with lots of little round-ish stones in it. Perhaps a home-made mix of some kind? The building has been there since pre-1948. Basically, it's not the smooth, homogenous concrete you'd expect to see poured today.

I say the back seems unsupported because the back wall to the ground is wooden, and doesn't seem solid enough to me to be bearing any real weight. But it could be. All I can say is that I couldn't knock it out with my bare hands.

This image is of the back corner where the separation of the side concrete and back wooden walls is clearly evident. This gap measures about 3.5" at its widest (top), and has probably increased about 2" in the last 2-3 years.

This image is of the other back corner, on the downslope side (meaning the building is leaning downhill toward this corner). Here, there is less separation on this side, but the angle of the side wall is still easy to see.

Both side walls show a pronounced bow front-to-back, and both are severely cracked top-to-bottom. I think is essentially creating extra movement, as the walls are now no longer one solid piece, but really four that can now move separately.

I think the building is getting to the point where it's leaning so badly that it must either be re-seated or torn down. I would like some advice on how you would go about trying to save the building. Or if it's an obvious lost cause.

Answer 1

Ultimately, I decided to save it. I used stacks of cribbing with large beams to jack the building up off of the failing foundation walls. Similar to this (much larger) example:

Once I had it up on the crib stacks, I was able to remove the jacking beams, pour concrete footers/piers, and set 6x6 posts. The building now rests on those posts and sits firmly. Once closed up, it became a nice storage space.

Answer 2

In lieu of expensive underpinning or buttressing, you could use tie-bars and plates. This method is commonly used to strengthen old brick (or other masonry) structures in areas prone to seismic activity.

You would drill through the foundation walls below floor level and run several iron tie-bars all the way through, with gusset plates on the outside. On buildings that small I have seen them used to pull the foundation walls back to plumb using threaded fittings and/or turnbuckles. They would definitely help reduce future movement.

Of course a new foundation is the best way. But tie-bars are an inexpensive choice (especially for that small building) that would likely give you some time if you would like to save the structure.

Answer 3

A new garage is like five grand...

Foundation work on that building has got to come to at least half that, and then you've still got a rotted liability sitting on top of it.

If you're going to do it yourself, you're looking at a hell of lot of work, for a building you'd better be in love with or have historical restrictions on.

If the foundation is creeping an inch per year, then it's not below your climate's frost line. Insure any new pour is. IMO, it's not worth the work it would take to bring everything up to snuff (I'm assuming the inside has seen better days also). You've got to do something though.

Buttressing is an option, but one so ugly that I hesitate to suggest it. If it really must be saved, it'd have to be buttressed one way or another. Either with metal stilts angled to a secondary foundation to halt the creep, or a complete encasement and underpinning of the existing foundation.

However, if the existing concrete is crumbling, you are out of (non-expensive/ time-consuming) options. The foundation would need to be replaced in full, using a piecemeal approach.

Google search "underpinning" for contractors in your area, unless you really want to dig holes all summer...