Houses built on fill

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Submitted by bibsoconner on March 16, 2012 - 10:53am

Any opinions on buying houses that are built on fill as opposed to bedrock? Can someone tell me how common houses that are built on fill are in San Diego? I'm looking at a 1960s house (slab foundation) built on fill. I realize bedrock is preferable, but perhaps it's not uncommon to have houses built on fill in San Diego.

My specific questions:
1. Is it still legal to build houses on fill?
2. Anything special to consider for houses built on fill? I have already found out that the bedrock (Shale & clays) are 20 feet down and are sloped away from the canyon, which is good).
3. How common are houses built on fill.
4. Would you go for it? Any parting thoughts?

Many thanks in advance,
Dave

Submitted by Blogstar on March 16, 2012 - 11:29am.

1) Yes, with proper compaction reports.
2)I would rather buy an older house on fill than a newer one and do due diligence as you are.
3)Common in SD county.
4)It depends. If the entire yard has steep areas, I don't like that. If given a choice I would chose to build a stepped foundation over a slab on fill.

I have seen a pad built where some native soil should have been removed and better fill brought in and it was not done. Maybe you could dig around the footing, especially on the low side and check for type of soil. Good fill can compact as hard as undisturbed soil that is suitable to build on.

Many areas of SD have what is called "expansive soil", Check into that.

Submitted by XBoxBoy on March 16, 2012 - 3:51pm.

We live in la jolla on mount soledad, and needless to say, a lot of the houses in la jolla are built on fill. (ours is not, but across the street where the views are better, are all on fill, dirt that was probably scrapped from our lot.) Depending on how nervous you are about things, how steep the canyon you are on is, etc. I would suggest a couple things.

1) During escrow hire a soils engineer to do a report for you. This might be a bit expensive, but could save you hundreds of thousands of dollars later. And a house built in the 60's probably had minimal compaction done.

2) Ask the soils engineer to give you a sense of what re-compaction would cost. Alternatively, many people in our neck of the woods have been putting in caissons and truss beams. Apparently they are about half the price of having the site re-compacted.

3) If possible, look into insurance issues. If you are on a canyon it might be very difficult to get homeowner's insurance for two reasons. 1) Fire, and 2) landslides. For instance I can tell you that AAA wouldn't even consider quoting anywhere near Mt Soledad. (We ended up going with Geico)

just my two cents.

XboxBoy

Submitted by UCGal on March 17, 2012 - 3:16pm.

I agree with xboxboy. Hire a soils engineer. Our house is a 1960's house... our lot slopes... but the did a cut/fill of the cobble/clay when they original developed the area in the early 60's. They did a good job. It's all native dirt - just cut from the high spots, and used for fill in the lower spots. They did good compaction.

When we built our casita we had to do proper compaction with a geotechnical company supervising. We were happy to have another set of eyes making sure the work was being done correctly.

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