General Contractor in Los Altos Hills

Los Altos Hills is entirely large-lot and largely hillside, with no commercial zoning at all. Grading, septic and drainage are routine parts of a project here in a way they simply are not on a flat valley lot.

What makes Los Altos Hills genuinely different is that the Town calculates how much house you are allowed to build, and slope is a direct multiplier in the arithmetic. Two numbers govern everything: Maximum Floor Area (MFA) and Maximum Development Area (MDA). Both come out of published formulas driven by your lot's average slope and its Lot Unit Factor. On a lot at 10% slope or less the MFA formula runs on 6,000 square feet per Lot Unit Factor; once average slope reaches 30% it drops to 5,000, and MDA falls from 15,000 to 7,500 across the same range. A steeper parcel is not merely harder to build on here. You are permitted less building on it.

Two details inside those formulas move real money. Floor area is measured to the outside of exterior walls and includes garage and carport space, which surprises people who assumed the garage was free. And floor area is counted twice where the vertical distance to the floor or roof above exceeds the Town's threshold — so a double-height entry or great room spends its square footage twice against a cap you cannot raise. Design that in before you fall in love with it. There is also a Parcel Water Budget to submit, calculated by the Town's own equation, which is not a step you will find in any neighbouring city.

The ADU rule here is unusually good and most owners do not know it. A new ADU up to 800 square feet is exempt from both MDA and MFA. Only floor area above 800 counts against your caps. On a lot where the main house is already at its limit, that 800 square feet is effectively additional entitlement, and it is the single strongest argument for an ADU rather than an addition in this town. Front setback is 40 feet with four-foot sides and rear, and the height limit is 16 feet — but hold a 30-foot side and rear setback and provide a parking space and the Town allows up to 19 feet and up to 1,200 square feet.

Run the MFA and MDA worksheets before anyone draws anything. The Town takes pre-application appointments with a planner at 650-941-7222, and an hour there is worth more than a month of design that the arithmetic will not support.

Permits. Work in Los Altos Hills is permitted through the Town of Los Altos Hills Building Department. We carry the submittal and the plan-check corrections — that is our job, not yours.

Los Altos Hills requires a pre-application meeting with a planner before you can apply for a building permit, and that meeting is where you are told whether a geotechnical report is needed. All permits submit electronically through eTRAKiT.

Pre-approved ADU plans. Los Altos Hills publishes a gallery of pre-approved ADU plans that homeowners can build from. Since AB 1332 took effect on January 1, 2025, California cities have had to run a pre-approved ADU plan program and post the approved plans publicly. Where a usable plan exists it can take real time and design cost out of a project, because the design has already been reviewed and only the site-specific work is left.