We start with your design. Modular is how we build it, not what you settle for.
Shape Homes · Where we build · Portola Valley
Two things make Portola Valley different from every town around it. Whether your project is ministerial turns on a percentage, not a size. And the Town has its own geologist.
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| Rule | What it says | Source |
|---|---|---|
| ADU, state-exempt size | 800 sq ft | Town ADU quick overview |
| ADU, local ordinance maximum | 1,200 sq ft | Town ADU quick overview |
| JADU | 500 sq ft | Town ADU quick overview |
| Height, detached up to 800 sq ft | 16 ft | Town ADU quick overview |
| Setbacks, rear and side | 4 ft minimum | Town ADU quick overview |
| Setback, front | Underlying zoning, including Scenic Corridor setbacks | Town ADU quick overview |
| Parking | None required | Town ADU quick overview |
| Decision timeline | 60 days from a complete ministerial application | Town ADU quick overview |
| Fire sprinklers | Typically required for newly constructed ADUs | Town ADU FAQ |
| Full ordinance text | PVMC 18.36.040 — confirm current text with the Town | PVMC 18.36.040 |
Rows marked unverified were read from a secondary source, not from the Town's own published document. We do not build to an unverified number. Every figure here is confirmed against the Town before your drawings start.
Size is rarely the constraint. These are.
Adjusted Maximum Floor Area is the governing local cap. An attached ADU that pushes the main residence past 85% of AMFA triggers discretionary review. So does an internal ADU over 1,200 sq ft, and so does a parcel adjacent to a Scenic Corridor. Two identical units on two identical lots can take completely different routes through the Town. We run the AMFA number first.
Portola Valley states plainly that certain parcels may be restricted with respect to proximity to earthquake faults and traces, and areas subject to active downslope movement. Applications route to the Town Geologist. This is not a formality on this side of the range, and it is the reason a lot check here starts with maps rather than a tape measure.
A Portola Valley application passes Building, Planning, Engineering, the Town Geologist and Woodside Fire Protection District. Where the parcel is on septic, capacity to serve the new unit has to be demonstrated to San Mateo County Environmental Health. Sequencing those five is most of the schedule.
Three from the library, chosen against this town's rules rather than its postcode.
Planning ranges, all in: factory package, delivery, foundation, utilities, permits and site work.
What moves a project inside its range is the lot, not the house. On Portola Valley parcels the items above are what usually decide it. A range is not a bid; a fixed price applies only as written in an executed construction agreement. See the plans or how the build works.
Most of our Portola Valley projects are called guest houses by the people who own them. A few are called pool houses, and one or two are called in-law cottages. Legally they are the same thing: an accessory dwelling unit. There is no separate guest house permit in Portola Valley. The rules described on this page, the size caps, the setbacks, the review path, apply to all of them, whatever the drawings call the building. That is good news. The ADU path is the fastest approval route available on a Portola Valley lot, so a pool house or in-law cottage designed as an ADU clears review sooner than the same building filed any other way.
Adjusted Maximum Floor Area is Portola Valley's local floor-area cap. It matters because ministerial versus discretionary review turns on it. An attached ADU that takes the main residence past 85% of AMFA goes discretionary. That is a different timeline and a different risk profile from a by-right approval, and it is decided by arithmetic you can do before you draw anything.
Up to 800 sq ft is state-exempt. Up to 1,200 sq ft is allowed under the local ordinance. A junior ADU is capped at 500 sq ft.
Portola Valley's front setback for an ADU follows the underlying zoning, including any Scenic Corridor overlay. On a corridor parcel that pushes the front setback well beyond the base zone. It is one of the few places where the front line, not the rear, decides where a second unit can go.
Typically yes for newly constructed ADUs. In a Very High Fire Severity Zone, conversions are workable but new construction requires a Planning Department check on street access, slope and road width before anything else.
Yes. In Portola Valley a guest house, pool house or in-law cottage is permitted as an accessory dwelling unit, so the size caps, setbacks and review steps described above apply exactly as written. The label on the drawings does not change the path. What changes the answer is the lot: its size, its slope, and what is already built on it.
We pull your parcel, the Portola Valley ordinance and a street view of the driveway before the call.
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