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basement under addition--bad idea?

Posted by fori (My Page) on
Thu, Sep 13, 12 at 13:46

I'm in an area of CA that doesn't do basements. Older homes have them, but most of what's out here was built after 1950 on crawl spaces or slabs.

We are in the early stages of planning an addition and wondering if a basement is a stupid idea. We can't build to over 17 feet at the top of the roof ridge but would certainly like to have double the space on the same footprint.

Are there reasons (other than expense which is probably pretty darn large in this seismically active area) not to put a basement in an addition? There must be a reason people don't do it here where people want bigger homes but don't want to move. Surely it's not because they didn't think of it! I must be missing something.

Follow-Up Postings:

RE: basement under addition--bad idea?

What would you do with all the dirt? (That is a serious question). Unless your lot is large enough and you have area you can legally fill, hauling out the basement dirt is probably going to be more expensive than adding more single story square footage.

RE: basement under addition--bad idea?

I realize this would be an expensive undertaking, but the extra square footage could be worth it. Maybe.

I'm going to assume dirt removal would be done by the builder. (Or excavator?) I'd probably rather not take on that job myself. :)

But no, the lot isn't big enough to spread it around. (If it were, I wouldn't want to stack my rooms!)

RE: basement under addition--bad idea?

Basements have largely gone out of favor because nothing is cheaper than building a slab on grade. Even crawl space construction has been abandoned in lieu of SOG!

In California (at least the Bay Area) one has to be concerned about expansive clay soils and thus, all below grade construction needs to be based on your specific soils conditions. In addition, proper waterproofing and drainage (sub-surface and surface) should be used.

That said, with the height and buildable area restrictions common in many areas in California, building a basement is an alternative to price out and consider. Good luck!

RE: basement under addition--bad idea?

So true, Virgil. I bet it would add 10x the inspections and permits and other bureaucratic details to the job.

And yet, I'm glad we can't build up. I've seen enough midcentury neighborhoods ruined by bedrooms tossed over garages and backyards shaded by neighboring additions. This neighborhood has larger lots than many of the time and area, but the houses are situated to run pretty much the width of the lot. So it does make a difference when someone goes UP.

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