Any experience building on Flag Lots?

Question

We own a SFH on 1/3 acre of land that's zoned SF-3. We have a 4,000 sq ft rectangular patch of grass that I'd like to explore building an ADU on. The lot is "Flag Shaped" meaning that this rectangle of grass is connected to the main street by a thin driveway that's about 25 feet wide (ie. we have 25 feet of frontage with the main street). On either side of this thin driveway is land owned by the neighbors.

I was told recently that under current city zoning laws ADUs are only permitted when there's frontage of 40 feet or more. Has anyone else explored something like this on Flag lots before? Thanks in advance!

I was told recently that under current city zoning laws ADUs are only permitted when there's frontage of 40 feet or more. Has anyone else explored something like this on Flag lots before? Thanks in advance!

David Ivy · Answer

@Jeff Tamaru

In addition to what @Kary Aycock said about the parking requirement, you should check whether your property is located within 1/4 mile of an "activity corridor." If so, then you are exempt from the parking requirement. You can check for that at this link. Have you found out anything from the city in the month since you posted?

Aaron Gordy · Answer

@Jeff Tamaru I believe that you can build an adu on it. To be sure, you should call the city of austin development assistance center. Google it for their number. They are very helpful in my experiences.

Account Closed · Answer

I invest in the Austin area and I don't know the answer to that one. However, there are at least two REIA's in the area and I'm sure someone will know or will know how to find out. Do a search for "REIA" and "RIA" in Austin.

Kary Aycock · Answer

Hey Jeff,

In most Austin neighborhoods you'll need minimum 5,750 sf and 50 feet of street frontage to build an ADU. Anything less than that is considered a sub-standard lot and not eligible for an ADU. However, some neighborhood plans (most of 78702, for example) have small lot amnesty and it might be possible on a smaller lot. You can build the lesser of 1,100 sf or 15% of the lot size for the ADU, but you also have to stay under .4 FAR (floor to area ratio). Parking can also be an obstacle, particularly with a flag lot, because you have to find room for at least one off-street space. Hope that helps!

Kary Aycock · Answer

Great link @David Ivy! I forgot about that exemption. It's actually pretty broad and covers a good amount of central Austin.

Any experience building on Flag Lots?

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