What should I know before I have my house's foundation redone?
February 19, 2006 10:36 AM   Subscribe

Might have to do some serious work on my house's foundation. Estimates run to $10,000 or more. What should I be asking or thinking about here?

I have a 1978 post-and-beam house where three of the posts rest directly on the hardpan under my house. The hardpan is then cut away to make room for a lower level. So half of the house rests on this dirt area that apparently is in danger of sloughing away. I've been told that I need a concrete retaining wall to keep this dirt foundation from sliding around, with all the dire consequences that would result for my house.

The Professional Engineer who did the assessment of the foundation made this recommendation:
One option is to construct a retaining wall to stabilize the soil that is currently supporting the concrete footings. This wall shall be constructed to an elevation so that at a minimum, the soil supporting each footing is at a grade that is no steeper than a 1 to 1 slope to the uphill side of the top of the concrete retaining wall. This wall should be constructed by a competent contractor and all plans should be reviewed by a professionally licensed engineer.

So now I'm starting the process of shopping around to get someone to do the work for me. So far my plan is to get a second opinion from another structural engineer, and to get at least 3 bids from construction companies to build a concrete retaining wall in the crawlspace under my house.

What else should I know or be thinking about?
posted by jojopizza to Home & Garden (4 answers total)
Did you have the house inspected before you purchased it? If so, and there is no mention of the problem in the report, you would probably have some recourse.

Have you had any moister problems in the past?

Do you live anywhere near a flood plane? If you do, a sump pump might not be a bad idea.

Are any of your floors sagging or have you had problems with doors sticking?

Don't expect any of the modifications you make to the foundation to be reflected in the future sale price of the home.
posted by 517 at 11:57 AM on February 19, 2006

Response by poster: Yes, we had the home inspected. The inspector estimated that a retaining wall for the foundation would cost around $1,000 to $1,500. We were stupid to not get a real estimate on that. But the house has appreciated considerably, so we're not too sore about the $10k.

The crawlspace does have moisture problems, and does have a sump pump system installed.

Yes, there are sagging floors above the crawlspace. The house inspector told us that this was pretty normal for a post-and-beam house.
posted by jojopizza at 12:04 PM on February 19, 2006

Engineers can differ greatly in their opinions, so you're wise to get advice from another engineer. We've had good luck asking experienced contractors, "Do you know a structural engineer who's practical and reasonable?" You want someone who will visit the site and look carefully, and who prefers a simple, elegant solution to an unnecessarily involved one. A good engineer with a lot of experience can save you a lot of money.

Something I personally hate: showing an engineer's plans to a contractor and hearing, "Well, that's one way to do it," or some other implication that they don't like the engineer's prescription. We avoid this by having a contractor make his bid based on advice from an engineer of his own choosing. This avoids the finger-pointing that happens later if a problem comes up, perhaps during the inspection by the building department.
posted by wryly at 12:54 PM on February 19, 2006

A retaining wall may be the cheap option but may not offer the safest solution. If I understand the situation correctly, a basic concrete block retaining wall may not offer the best support. How far away from the removed section are the posts? If it is close and a retaining wall has to cut away even more of the soil to be placed then I would advise against it.

The best solution is to place a permanent footing under the posts. You will need to temporarily support the posts and then dig away to place good solid footings below the grade of the lower level. this could be the most expensive and without details of the site and other situations of the house, this may not work.

Consider if the lower level is really worth the effort to have. If you can live without it, then it would be cheapest to abandon it and fill it in with slurry gravel.
posted by JJ86 at 8:20 AM on February 20, 2006

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