Los Altos ADU Builder: Design, Permits and Construction
Type Five designs, permits and builds custom ADUs in Los Altos, with one team from the first site visit to move-in. Los Altos approves ADUs with a building permit alone and allows detached units up to 1,200 square feet, so on most lots the real limits are setbacks, height, trees and budget.
Building an ADU in Los Altos
Los Altos is one of the more straightforward places on the Peninsula to get an ADU approved. The city reviews ADUs and JADUs ministerially: you need a building permit and any related permits, but no planning permit, public notice or hearing.
That doesn't make every lot simple. What usually sets the schedule and the budget is the stuff you can't see from the street: a protected tree near the best building spot, the run to your sewer lateral, or an electrical panel that can't carry a second home. The city allocates one sewer lateral per parcel whether or not you add an ADU, so your new unit ties into the line you already have.
Type Five is a design-build firm based in Berkeley, with architects and a general contractor under one roof. We design every ADU with our site-built modular system and build it on your lot with conventional wood framing. You get set layouts and pricing you can plan around, and a home fitted to your site rather than dropped onto it.
As seen in the New York Times.
Los Altos ADU rules at a glance
Rule | Detached ADU | Attached ADU | JADU |
|---|---|---|---|
Maximum size | 1,200 sq ft | 1,200 sq ft, and no more than 50% of the main house | 500 sq ft, inside the house |
Maximum height | 18 ft | 16 ft, or the zoning district height if greater | N/A |
Side and rear setbacks | 4 ft | 4 ft | N/A |
Front setback | Per zoning district | Per zoning district | N/A |
Separation from other buildings | 5 ft | 5 ft | 5 ft |
Parking | Required, with exceptions | Required, with exceptions | None |
Owner occupancy | Not required | Not required | Owner must live on the lot |
Three ways to permit an ADU in Los Altos
The city gives homeowners three routes, and it helps to know which one you're on before anyone draws a line.
- Custom plans. A designer draws an attached or detached ADU for your specific lot and submits it for a building permit. This is how Type Five works.
- Pre-approved plans. Private designers submit standard detached ADU plans that the Planning and Building Divisions review ahead of time. You buy the plans and add your site details.
- City permit-ready plans. Los Altos offers free detached ADU plans in three sizes (525, 854 and 1,190 sq ft) and three styles. You can pick from set options, but the city doesn't allow modifications.
Standard plans can save design time on a flat, open lot. If your best building spot sits near a protected tree, your lot slopes, or you want the ADU to work with the main house, a custom design is usually the better fit. Either way, the site work, utilities and construction still have to be planned for your property.
How long a Los Altos ADU takes
Think of it as three phases: design, permitting and construction. State law gives cities 60 days to approve or deny a complete ADU application, but each round of corrections adds time.
Across 15 Type Five projects first submitted between June 2025 and May 2026 that now have a building permit, the median time from first submittal to issued permit was 120 days. The fastest took 50 days and the slowest 196. Projects still in review aren't in that number, so treat it as a best-case benchmark, not a promise. Our permit speed guide compares Bay Area cities using public data.
Construction comes after the permit. You can see how we sequence a build on our build schedule page.
What sets Type Five apart?
Most Los Altos homeowners talk to an architect, a few contractors and maybe a factory-built option before they decide. Here is what working with us looks like.
- One team. Design, engineering, permits and construction stay with Type Five, so nobody points fingers when something changes.
- A fixed budget before you build. We look at your actual site and give you a guaranteed budget for the whole project before construction starts.
- Built on site, built to last. Every ADU is wood-framed in your backyard. No crane day, no factory box, and no guessing whether a module will fit down your driveway.
- Design you can configure. Our software lets you try layouts and finishes online before we refine the plans with you.
What our clients say
Don’t just take our word for it. Read more in-depth client testimonials.
"The design process with Type Five felt more streamlined, and the experience allowed us to stay focused and avoid being overwhelmed by too many options."
“I feel like we got all the benefits of a custom build, without the uncertainty.”
"Type Five was really attractive because that's what they were offering: a full-service construction company with an established design system."
Tell us about your Los Altos ADU
Every lot is different. Tell us about your property and what you want the ADU to do, whether that's housing a parent, a rental or a place for adult kids, and we'll walk you through what it would take.
How our process works
One team takes your project from first sketch to move-in, with a fixed budget before construction starts.
FAQs about building an ADU in Los Altos
Short answers to the questions Los Altos homeowners ask us most.
Do I need a planning permit for an ADU in Los Altos?
No. Los Altos reviews ADUs and JADUs ministerially, so only a building permit and related permits are required. There's no planning permit, public notice or hearing.
How big can an ADU be in Los Altos?
A detached ADU can be up to 1,200 square feet. An attached ADU can also reach 1,200 square feet but can't exceed 50% of the main house. A JADU, built inside the existing home, tops out at 500 square feet.
How tall can a detached ADU be in Los Altos?
The city's ADU Information Guide lists 18 feet for a detached ADU, with 4-foot side and rear setbacks and 5 feet of separation from other buildings.
Can I use the city's free permit-ready ADU plans?
Yes, if your lot is eligible. Los Altos offers free permit-ready detached plans at 525, 854 and 1,190 square feet in three styles, but they can't be modified. Type Five designs custom ADUs, which makes sense when your lot, trees or goals don't match a standard footprint.
Do I pay impact fees on a Los Altos ADU?
Not on an ADU of 750 square feet or less, which is exempt from impact fees. Larger units may be charged local impact fees. School, permit and utility fees are separate. Our Bay Area ADU cost guide breaks down the full budget.
Does an ADU need its own sewer connection in Los Altos?
Usually not. The city's current policy allocates one sewer lateral per parcel, regardless of whether it has an ADU. You may still need to upsize utilities for the added load.
How long does it take to permit an ADU?
Across 15 Type Five projects first submitted between June 2025 and May 2026 that now have a building permit, the median time from first submittal to issued permit was 120 days. The fastest took 50 days and the slowest 196. State law gives cities 60 days to act on a complete application.
Are you a prefab ADU company?
No. Type Five is a design-build firm, and we build every ADU on site with conventional wood framing. Our site-built modular design system gives you some of what people like about prefab, like set layouts and clear pricing, while the home itself is built from the ground up to fit your lot.