ADU Design & Build · Los Altos
ADU Builder in Los Altos
Real guest houses, not squeezed-in rentals — Los Altos' quarter-acre lots host 1,000–1,200 sq ft detached units with setbacks to spare.
Los Altos is quiet money — rancher-era homes on quarter-acre lots, a walkable village, and one of America's wealthiest zip codes choosing understatement over display. ADUs here are guest houses in every sense: 1,000–1,200 sq ft, full kitchens, vaulted ceilings, private orientation, finished to the main home's standard.
The lot sizes change the playbook entirely. Where Sunnyvale squeezes a 600 sq ft ADU behind a ranch, Los Altos hosts a true guest house with proper setbacks to spare. And in Los Altos Hills — a separate town — slope, septic capacity, and WUI fire-zone factors make experienced site assessment essential before any promise gets made.
We handle the whole arc: feasibility on your parcel (including Hills site factors), a design that satisfies ADU law and local standards, the 60-day permit, and fixed-price construction with the site work estate lots can require.
ADU permits in Los Altos
Los Altos Building Division (1 N. San Antonio Rd.) holds the 60-day state clock for compliant ADUs; the city's generous lots make compliant siting straightforward. Los Altos Hills is a separate town that adds site-development review for slope, septic, and fire factors — much of it is WUI fire zone. We confirm which jurisdiction governs your parcel and design accordingly.
What’s included
Estate-Lot Feasibility
Setbacks, utilities, septic (Hills), and fire-zone standards assessed on your Los Altos parcel before design spend.
Guest-House ADUs (to 1,200 sq ft)
True guest houses — full kitchens, vaulted ceilings, private orientation, finished to the home's standard.
Los Altos Hills Site Work
Slope analysis, septic capacity, and fire-hardening folded into Hills projects, priced upfront.
Design Tuned to Local Standards
Massing and siting that satisfy ADU law and the town's expectations so approval stays on the 60-day clock.
Financing & Fixed Pricing
Cost/rent/payback modeled upfront; locked construction pricing with milestone payments.
What it costs in Los Altos
| Project | Typical Range | Notes |
|---|---|---|
| Conversion / smaller detached | $220K – $360K | Estate-standard finish |
| Detached guest house (800–1,000 sq ft) | $340K – $560K | $400–$600/sq ft |
| Large guest house (1,000–1,200 sq ft) | $460K – $720K | Full 2BR, vaulted, estate finish |
| Add: Los Altos Hills site work | $30K – $150K | Slope, septic, fire hardening |
Los Altos and Los Altos Hills sit at the county's top tier for both cost and rent/resale value, so the guest-house investment holds.
What we build in Los Altos
- 1,000+ sq ft guest-house ADUs near the village
- Los Altos Hills estate ADUs with slope & septic work
- Detached units in Country Club & Woodland Acres
- Multigenerational guest houses on quarter-acre lots
- Garage/interior conversions finished to home standard
ADU Design & Build — full details
Process, scope, and everything our adu design & build service covers Bay Area-wide.
All services in Los Altos
Remodels, ADUs, permits, real estate, and financing across Los Altos.
Los Altos ADU Design & Build FAQs
Can I build a large guest house in Los Altos?+
Usually yes — state ADU law guarantees the baseline, and Los Altos' lot sizes comfortably host 1,000–1,200 sq ft detached units (the practical ceiling under most local standards). We design them as true guest houses: full kitchens, vaulted ceilings, private orientation.
What does a Los Altos ADU cost?+
Detached guest houses run $400–$600/sq ft given the finish standard — roughly $340K–$560K for 800–1,000 sq ft and $460K–$720K for a full 1,000–1,200 sq ft 2BR. Los Altos Hills site work (slope, septic, fire) adds $30K–$150K where it applies.
Do you build in Los Altos Hills too?+
Yes, with the added discipline Hills parcels demand: slope analysis, septic capacity, fire-hardening (much of the town is WUI fire zone), and the town's site-development process. Our feasibility work answers those before design money is spent.
Will an ADU's rent justify the Los Altos cost?+
At Los Altos rents and resale values ($1,800–$2,800/sq ft), yes — a guest-house ADU both rents at the top of the market and adds square footage that appraises at Los Altos prices. Many owners also value the multigenerational flexibility first.
How long does a Los Altos guest house take?+
Typically 11–16 months end to end; Hills parcels run longer where slope, septic, and site access add design and construction time. Feasibility gives you a realistic schedule for your specific lot.
Related Services & Guides
ADU Design & Build
Backyard homes that pay for themselves: feasibility, design, 60-day permits, financing, an…
How Much Does an ADU Cost in California? (2026 Breakdown)
Real 2026 ADU costs: garage conversions $125K–$220K, detached units $350–$550/sq ft. Line-…
ADU ROI Calculator: Cost, Rent & Payback for Your Bay Area Lot
Interactive ADU ROI calculator with 2026 Bay Area numbers: estimate construction cost, mon…
Remodeling Contractor · Los Altos
Expansive single-story living done right — whole-home remodels and estate renovations on L…
Los Altos Contractor
Premium design-build for Los Altos & Los Altos Hills: whole-home remodels, additions, gues…
Planning adu design & build in Los Altos?
Honest numbers, one accountable team. We respond within one business day.
Licensed · Bonded · Insured · CSLB #1056408 · Serving all of Silicon Valley