How to fix a house's foundations?

November 21, 2009 10:52 PM

After noticing some small cracks on the interior walls of one room, I went outside and saw several HUGE zig-zag cracks have appeared between the bricks at the back corner of my house. All the indications of a bad case of subsidence. Time to panic; the house is now worthless! What are my options?

From my googling, it seems that a structural engineer will have to come in and fix the foundations. How much does this cost in general - all I know is that it will be an absolute fortune, and insurance (in Australia) does not generally cover it. I'm f*cked!

posted by moorooka to Home & Garden (11 answers total)

This is a fairly common occurrence in San Antonio, USA, where I used to live. They come in, dig under, jack it up, and go. It's a pretty smooth process. It is expensive, but expensive in like TV terms, not BMW terms.
posted by sanka at 10:57 PM on November 21, 2009

Best answer: Here, the worst case scenario is quoted at around $60-80,000 and the best case as maybe building a retaining wall to shore things up, or leaving it alone for free.

There's a product called Helifix that purports to offer a cost-effective solution to subsidence - YMMV.

From your username, I'm guessing you're in Brisbane? These guys offer a free initial inspection.
posted by t0astie at 12:44 AM on November 22, 2009

Response by poster: the worst case scenario is quoted at around $60-80,000

thanks for the info, but.... God.
posted by moorooka at 2:03 AM on November 22, 2009

Eh ... depends on what the house is built on, how old it is, etc. Used to live in Stanmore (Sydney), which is mostly built on an old brick pit. The clay swells when it rains, which makes one set of cracks open up; then, when the ground dries out, there's a brief period when the cracks close up (and people paint); then, as drying proceeds further, a different set of cracks open up. Cycle annually.

Of course, your definition of huge cracks may be different; I'm used to something in the 5mm range on a double-brick house.
posted by nonspecialist at 3:38 AM on November 22, 2009

Don't commit fraud. Yes, people do it.
posted by fourcheesemac at 6:12 AM on November 22, 2009 [1 favorite]

We had it done (structural engineer / dig big hole / back fill with concrete) a few years ago in Toronto for about $20k. It's a must-fix, as letting it just go is not really an option. It will get worse and your house will keep sinking and breaking.
posted by y10k at 6:28 AM on November 22, 2009

I had the Helifix repair done on my place a year ago (clay soil, huge tree in neighbour's yard, a couple of hot summers, followed by a couple of wet ones.) Mine was covered by insurance, and the biggest inconvenience was the wait - it had to be monitored for at least a year to see if there was any further movement - and during that time I was reluctant to spend my own money redecorating and renovating my flat if it would all have to be done over at the insurer's expense should the remedial work prove extensive.

It wasn't that big a job, as it turned out - the Helifix bars took about a week to install, on two sides of the building.
posted by essexjan at 7:23 AM on November 22, 2009

As the engineer /surveyor/ whatever they call themselves in first. This shouldn't be hugely expensive. I've used them on a few occasions and can't remember the visits being more than a few hundred pounds (in London). FWIW ours told me not to worry about cracks until I could get my finger in them.

If you do need underpinning, as a number of posters say, it's usually a case of putting big chunks of concrete under the offending wall. Or perhaps you just need a wall rebuilding or some of the wall rebuilding. Whatever, you need to get a structural engineer.
posted by rhymer at 10:02 AM on November 22, 2009

What kind of dirt is your house built on? Do your neighbors have foundation problems from time-to-time? Are there thirsty trees near the house?

Where I live, in Houston, the clay is responsible for a lot of foundation issues. Here, you cannot just raise one corner, because that location will be fixed in place while the rest of the house moves with the shifting soils. The whole thing has to go up on pilings driven into the soil, down below the zone affected by changes in moisture content. I hope that this is not the case for you. $20,000 +/-.

Perhaps you have a plumbing issue, where the soil has been washed away. Less expensive.

If you patch the cracks without fixing the problem, the next buyer's inspector will figure that out quickly. If you patch the cracks and then fix the problem, you could shatter your bricks, so don't do that.

Good luck.
posted by Midnight Skulker at 11:18 AM on November 22, 2009

Note that the 60-80 figure is *worst* case.

Here in Texas, we have the same sort of clay soil... assuming that you've got a slab foundation? They backfill it, then they reinforce the foundation with cables and try to get it to line up again. Doesn't sound like yours is that bad yet. Make sure you take care of it before it gets that bad!
posted by SpecialK at 11:36 AM on November 22, 2009

Response by poster: thanks everyone.

time for another mortgage. and a good scream.
posted by moorooka at 2:21 PM on November 22, 2009