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So You Want to Build an Iceberg Home: A FAQ

The lowdown on going low down.

Editor's note: Read more about the iceberg home trend here. And here's a look inside four subterranean iceberg homes across the Bay Area.

I want to build a basement. What am I looking at? Contractors and architects say that well-finished basements cost about as much as upstairs spaces to build on a per-square-foot basis. At the high end, that means anywhere from $550 to $1,000 per square foot. Complicated excavations and underpinning can add to the cost, as can building a basement larger than the footprint upstairs. Then, of course, it depends on what you want to put down there. An indoor pool, obviously, would cost extra.

How hard is it to add a basement to an existing home? Pretty hard. Basements are easier to build below homes when you’re starting from scratch, but below-grade garages can be converted into basements without too much difficulty. John Fox, a San Francisco–based contractor, says that the city is encouraging new ways to create additional living spaces, so garage-conversion permits have gotten easier to obtain over the past year or so. Crawl spaces can also be dug out into full-height living spaces—for a price, of course. In dense parts of San Francisco, adding a basement to an existing home can involve shoring up your property against neighboring houses, which gets complicated.

How far down can I go? It depends on your particular location. Contractors say that going two full stories down is still a rare request, but it’s been done to accommodate something very large—like an indoor basketball court—or to include a garage in addition to a belowground level of living space.

How do I make a basement feel like it’s not a basement? Architects say it’s a good idea to make the ceilings as high as possible (at least 10 feet), carve out patios that will act as light wells, and heavily waterproof floors and walls so the space never gets that damp, basementy smell. Some interior designers say it’s also a good idea to extend the upstairs flooring and finishes into the basement to create a visual flow.

Speaking of dampness, what’s the deal with groundwater? In many parts of the Bay Area, a low water table means that groundwater removal, or dewatering, is part of the basement excavation process. In Palo Alto, new rules require that dewatering happen in the dry season (from April to October). Perhaps not surprisingly for a tech-heavy town, contractors have begun using cutting-edge technology to build cutoff walls that eliminate the need for dewatering altogether.

How will a basement affect my home’s resale value? Real estate agents say that well-finished basements can add value to homes, particularly in areas where existing home sizes are relatively small. “No one has ever come to me and said, ‘I have to have a basement,’” says Julie Ray, a real estate agent with Coldwell Banker. “It’s more about, ‘I need to have 4,000 square feet,’ or a separate area for the kids or for entertainment”—areas that often need to go underground because of aboveground space restrictions. In the long run, a well-built basement can easily pay for itself.


Originally published in the April issue of San Francisco 

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