So I was taking a walk in Palo Alto today -- I think along Webster Street -- and noticed one of those (common in Palo Alto) new-ish homes with fancy light wells for the habitable space in the basement. (It's popular because basements don't count as floor area for zoning code!)
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But this one was unusual. Unlike most of the fancy new houses I walk past in Palo Alto, this one was single story. Single story plus a fancy habitable basement, that is. At first glance that seemed odd.
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But then I started to think about Palo Alto's zoning code for the R-1 zone. (See library.amlegal.com/nxt/gate… section 18.12.) And I remembered that single-story houses are allowed to cover more of the lot than multi-story houses, to allow them to have the same limit on floor area.
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But, if you (unlike the law) think of the habitable basement as floor area, this means that a single story house with a basement is allowed to have *more* floor area than a multi-story house on the same lot, since the above-ground limit is the same but the basement can be bigger.
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So this means that someone constructing a single-family house in Palo Alto who wants to maximize floor area, doesn't care about a lot being in the basement, and doesn't care about reducing the size of the garden/lawn/etc., actually maximizes floor area by building single-story.

Nov 28, 2020 · 6:20 AM UTC

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Of course, this seems rare, I suspect because single story houses don't *look* fancy. Maybe also because people like multi-story layouts.. But I like to think it's the former. Anyway, that's today's tale of how the math in the zoning code changes the buildings around us.
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Postscript: I walked by again today to confirm what I'd seen. The construction plans from 2014 (record 14PLN-00140) aren't online anymore, but the description is "for construction of a new 3,240 square foot home and basement on an existing vacant lot in the R-1 zoning district".