How Much Can You Build on a Lot in San Carlos?

August 22, 2013

Size Matters.

This is a natural segue from our discussion yesterday on expanding a 3-bedroom home into a 4-bedroom in San Carlos.  As a homeowner or prospective buyer in San Carlos, one of the first questions that you have to answer when it comes to expansion is can you even do it?  Finances notwithstanding, will your property be able to accommodate the expansion that's required to add that coveted 4th bedroom?

How much you're able to build on a lot in San Carlos is probably the most common question that gets asked by buyers and homeowners — and unfortunately it's one of the most misunderstood topics.  That's because there are a whole slew of factors that go into calculating how much a given lot can be built on.   The purpose of this post is to give you a very general guideline on how much you can build on a lot, and more importantly, who you can contact when you have questions about this.

All About Lot Coverage.

Here's a very handy general guideline that was created by the City of San Carlos Building Department.  If you take nothing else from this post, take this:  RS-3 and RS-6 Zoning Summary

One of the most important metrics on this summary is Lot Coverage.  Think of Lot Coverage as a bird’s eye view of the lot, looking at coverage of structures (including garage, but not landscaping, driveways or any structure under 18” in height).   In other words, the footprint from above.  From the spreadsheet, the maximum lot coverage allowed is 40% for a flat lot, and slightly less for sloped lots.   However, in some instances the City will allow lot coverage up to an absolute max of 50%, especially for smaller lots.  But the more you push beyond 40%, the more your design will be scrutinized by the City.

The other key metric to pay attention to is Floor Area Threshold.  This is defined as the amount of square footage taken up by the the living space and garage.  Again, the cap is set at 40% of the lot size, but there are provisions for owners to build a minimum of 3,000 square feet on virtually any lot.   This exception allows larger homes to be built on some of the smaller lots that you find in the lower part of White Oaks and Oak Park.

These two guidelines must both be satisfied to determine how much you can actually build on a given lot.   Here's a typical example of what you might encounter in the flats:   On a 5,000 square foot lot, you can actually build a 3,000 square foot home (including the garage).  But the maximum allowable footprint would be 2,500 square feet (5,000 sq feet x 50%).   The remaining 500 square feet would have to be on the second floor, or as a basement.  Again, this exception is subject to staff approval by the City.

It's important to reiterate that this post is simply a general guideline to what you're able to build on a piece of property in San Carlos.  If you have specific questions, or need further clarification on the attached worksheet, contact Gavin Moynahan in the San Carlos Building Department at 650-802-4267, or click here to send him an email.  (Special thanks to Gavin for the background info for this post).

Stay Local.

Finally, if you're planning an addition or a major remodel, or your seeking out a property to accommodate this, I cannot stress enough that you should team up with a designer or architect who knows San Carlos and understands how their Building and Planning Departments operate.   That's literally the difference between a project that goes off without a hitch, and one that gets red-lined 9 ways from Sunday.   We went through this exact process about 13 years ago, and were lucky enough to work with an architect with a proven track record in San Carlos.  It makes a difference.

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