ADU Costs in Los Gatos, California

Planning-level pricing guide by ADUWizard.com
Updated for 2026 budgeting

Los Gatos is a small town with a big price tag, and the reason isn’t just that it’s next door to San Jose money. It’s the hills. A meaningful share of Los Gatos lots sit in the foothills west of downtown, and a hillside lot changes an ADU budget before a single stud goes up: geotechnical review, engineered grading, retaining walls, and access work that a flat lot in Willow Glen never has to pay for.

I’ve bid Los Gatos jobs that looked identical on paper to a San Jose job two miles away and came in $60,000 apart, purely because one sat on a slope and the other didn’t. That gap is the real story of this market, more than square footage or finish level.

What Changed in Los Gatos for 2026

Start here, because Los Gatos is actually mid-rewrite right now, not sitting still.

The town’s ADU ordinance (Town Code Chapter 29, Article I, Division 7) dates to 2020, and California’s Housing and Community Development department sent Los Gatos a formal findings letter on that ordinance back in October 2023. The town is now working through another update to bring its local rules in line with current state law. The Planning Commission reviewed a draft ordinance on June 10, 2026, and forwarded a recommendation to the Town Council. If you’re reading local ADU rules anywhere online, including this page, confirm the current version with the Community Development Department’s Planning Division before you finalize plans, because this is a moving target this year.

That update matters more than it used to. A 2025 amendment to SB 9 gave HCD real teeth: if a local agency’s ADU ordinance doesn’t comply with state law and the agency doesn’t fix it, the ordinance can be declared null and void, and the town falls back to bare state standards until it adopts something compliant. Given that Los Gatos already has an open HCD findings history, this isn’t an abstract risk for the town, it’s the reason the rewrite is happening now.

Separately, four state bills took effect January 1, 2026, and they apply here regardless of what Los Gatos’s own ordinance says. AB 1154 narrows JADU owner-occupancy requirements so they only apply when the JADU shares a bathroom with the main house. SB 543 shifts how ADU size gets measured to interior livable space, locks in a 15-day application completeness clock, and expands the development impact fee exemption to any ADU at 750 square feet or less (500 or less for a JADU). AB 462 mostly affects coastal-zone and disaster-rebuild ADU permitting, which has limited relevance for landlocked Los Gatos, but it’s worth knowing it exists if your project ever touches a declared disaster area. The 2025 SB 9 amendment I mentioned above is the fourth.

What an ADU Actually Costs in Los Gatos

For our full statewide picture, see our California ADU cost guide, which puts the state average somewhere in the low-to-mid $300Ks. Los Gatos runs well above that, and it’s not close.

Three things push the number up here. First, labor: this is the same skilled trade pool serving San Jose, Saratoga, and Los Altos, and it prices accordingly. Second, land and lot conditions: Los Gatos has a lot of narrow, older lots downtown and a lot of sloped lots in the hills, and neither is cheap to build on. Third, finish expectations: homeowners in this market tend to want a unit that matches the main house, not a budget box.

Honestly, the hillside piece is the one people underestimate most. I’ve had homeowners budget like they’re building in flat Sacramento and then get hit with a geotechnical report, an engineered foundation, and a retaining wall quote that adds up to more than their entire finishes budget. The same math I described for Almaden and Evergreen in my San Jose cost guide applies here, just more often, because a bigger share of Los Gatos parcels sit in the hills relative to the town’s total land area.

Component	Cost range	Notes
Site work, access, utilities	$25,000-$120,000	Flat lots at the low end; hillside lots with retaining walls and long utility runs at the high end
Foundation (incl. geotechnical on slope)	$30,000-$90,000	A geotech report and engineered foundation are typically required once slope triggers it
Framing and shell	$80,000-$160,000	Premium regional labor rates apply regardless of lot type
MEP (electrical, plumbing, HVAC)	$50,000-$100,000	Higher on detached units needing new utility runs from the main house
Interior finishes	$50,000-$130,000	Silicon Valley finish expectations push this well above the state average
Design, engineering, permits and fees	$25,000-$70,000	Geotechnical and structural engineering add real cost on hillside lots
Contingency	$20,000-$70,000	Budget higher on any hillside or older-lot project

Source: ADU Wizard builder estimate

Size	Low finish	Mid finish	High finish
400 sq ft	$190,000	$230,000	$290,000
600 sq ft	$250,000	$310,000	$380,000
800 sq ft	$320,000	$400,000	$480,000
1,000 sq ft	$390,000	$480,000	$580,000
1,200 sq ft	$460,000	$580,000	$750,000

Source: ADU Wizard builder estimate

Our Data Hub tracks these ranges as bids come in, and the spread on Los Gatos projects specifically has been wider than most cities we track, which tells you the lot matters more than the floor plan here.

Fees and Exemptions in Los Gatos

Let me be straight about what I could and couldn’t confirm here.

I pulled the Town of Los Gatos Community Development Department’s own fee schedule, effective July 1, 2026. It covers Planning Division applications: Architecture and Site review, Development Review Committee approval, Planning Commission hearings, variances, and so on. Almost none of that schedule actually applies to a standard ADU, because state law (and Los Gatos’s own Town Code Section 29.10.305) requires ADU applications to be reviewed ministerially, without a public hearing and without discretionary Architecture and Site or Planning Commission review. The one ADU-specific line item on that schedule is a real waiver: the use and occupancy clearance fee for “occupancy of a new secondary dwelling unit” is listed as No Fee, flat out.

Here’s a comparison that shows what that actually saves you. That same fee schedule lists the Architecture and Site application fee for a new single-family home in the Hillside Residential (HR) or Resource Conservation (RC) zone at $25,769.76 in Development Review Committee fees alone. Your ADU doesn’t pay that, because it isn’t routed through discretionary review the way a new house on a hillside lot is.

What I could not find is a single published flat dollar figure for ADU building permit fees, since those are calculated off construction valuation by the Building Division rather than listed as a static number on the planning fee schedule I reviewed. Unverified exact figure: confirm your specific building permit cost with the Building Division (Building@LosGatosCA.gov, 408-354-6876) before you budget off any article, mine included.

Beyond that use-and-occupancy waiver, I did not find a separate, Los Gatos-specific ADU impact fee waiver or reduction in either the Town Code or the fee schedule. What applies here is the same state-level relief every California city has to honor: under SB 543, development impact fees can’t be charged on an ADU at 750 square feet or less, or a JADU at 500 square feet or less. That’s a state floor, not something Los Gatos added on top. If you’re comparing markets, that puts Los Gatos in the same category as San Jose, Riverside, and Long Beach: no local fee waiver beyond what the state already requires, verified against the town’s own current fee schedule rather than assumed from a neighboring city’s rules.

Los Gatos-Specific Factors That Move the Number

Hillside lots go through a different design path, not just a steeper driveway

Los Gatos adopted its Hillside Development Standards and Guidelines back in January 2004, and they apply to new hillside homes and major additions or remodels in the hills. The town’s own Hillside Residential (HR) zone standards describe the intent plainly: minimize grading, protect natural terrain, and reduce erosion, geologic hazard, and fire hazard exposure through a slope-density formula.

Here’s the part that actually matters for an ADU specifically. Under Town Code Section 29.10.320(3)(d), accessory dwelling units in the HR and RC zones don’t use the flat four-foot setback that applies in the R-1, R-D, R-M, RMH, and R-1D zones. Instead, they have to sit within the Least Restrictive Development Area, the buildable envelope the town identifies through a constraints analysis of the lot’s slope, access, and geologic conditions. Practically, that means your ADU’s location on a hillside lot isn’t really yours to pick freely; it’s wherever the LRDA says you can build, and figuring that out usually means a constraints analysis before you can even finalize a site plan.

The general ADU rules, for context

Los Gatos allows ADUs on lots in the R-1, R-D, R-M, R-1D, RMH, HR, and RC zones (Town Code Section 29.10.320(2)). Maximum ADU size is 1,200 square feet with up to two bedrooms. Height is capped at one story and 16 feet in most residential zones, with some exceptions for units built into or above an existing two-story structure. Setbacks in the non-hillside zones are four feet from side and rear property lines, five feet from any other structure on the lot. One parking space per unit or bedroom (whichever is fewer) is required, with the usual state-driven exceptions: within a half mile of transit, inside a historic district, converted from existing space, and a few others (Town Code Section 29.10.320(8)).

Downtown’s historic overlay actually helps your ADU parking, not your design freedom

Los Gatos has a genuine Landmark and Historic Preservation (LHP) combining district layered over parts of downtown. If your ADU sits inside an architecturally and historically significant historic district, Town Code Section 29.10.320(8)(a)(2) exempts it from the off-street parking requirement entirely. That said, an ADU can’t be built in front of a primary dwelling that’s a designated historic resource, so the trade is real: easier parking, tighter siting.

Pre-approved plans exist, but don’t assume savings without checking

Los Gatos runs a pre-approved ADU plan gallery under California’s AB 1332 program, hosted at the town’s own ADU accelerator site. The catch the town states plainly: once you pick a pre-approved plan, modifications aren’t allowed, no matter how minor. That’s a real trade-off. On a flat, standard lot, skipping custom design review can save real money and time. On a hillside lot governed by the LRDA, a catalog plan often can’t be sited without a site-specific supplement anyway, so the savings shrink fast.

Tight, older lots downtown are their own budget problem

Separate from the hills, a good chunk of Los Gatos’s flatland lots near downtown are narrow, older parcels with tight side yards and older utility infrastructure. That’s not a hillside problem, but it drives up sitework and utility trenching costs in its own way, and it’s easy to forget about when everyone’s talking about slope.

What I’d Budget If I Were Building Here

If I were building a detached ADU on a standard, flat Los Gatos lot today, I’d budget $420,000 to $480,000 all-in for something in the 800 to 1,000 square foot range with a finish level that matches the neighborhood. If the lot is anywhere in the hills, I’d add a firm $60,000 to $100,000 before I looked at a single finish selection, and I wouldn’t finalize a floor plan until the constraints analysis told me where the LRDA actually lets me build. That order of operations matters more here than in almost any other California market I work in.

For the permitting mechanics themselves, our California ADU permit guide and the broader permits pillar cover the state-level ministerial process that Los Gatos has to follow regardless of its local ordinance rewrite.

FAQs

How much does an ADU cost in Los Gatos in 2026?

Budget $190,000 on the low end for a small conversion project and up to $750,000 for a larger detached unit on a hillside lot with a premium finish package. Most standard, flat-lot detached projects land in the $420,000 to $480,000 range.

Does Los Gatos waive any ADU fees beyond what the state requires?

The town waives its use and occupancy clearance fee for new secondary dwelling units outright, per its own Community Development Department fee schedule effective July 1, 2026. Beyond that, I did not find a Los Gatos-specific ADU impact fee waiver; what applies is the state’s own exemption for ADUs at 750 square feet or less under SB 543, the same floor San Jose, Riverside, and Long Beach also rely on.

Do I need special approval for an ADU on a hillside lot in Los Gatos?

You need to work within the Least Restrictive Development Area the town identifies for your lot under Town Code Section 29.10.320(3)(d), which usually means a constraints analysis before you can finalize siting. It’s not a discretionary hearing, since ADUs are still reviewed ministerially, but it does add real steps a flat-lot project skips entirely.

Does Los Gatos have pre-approved ADU plans?

Yes, through a plan gallery under the state’s AB 1332 program, hosted at the town’s own ADU accelerator site. Modifications to a pre-approved plan aren’t allowed at all, which makes them a strong fit for standard flat lots and a weaker fit for hillside lots governed by the LRDA.

How long does an ADU permit take in Los Gatos?

Plan on roughly 4 to 8 weeks for a complete, straightforward application, with the state’s ministerial review clock (15 days for a completeness check under SB 543, then a hard cap after that) as the legal backstop. Hillside projects needing a constraints analysis or geotechnical review should expect that pre-submittal work to add time before the clock even starts.

If you’re comparing Los Gatos against the market next door, our San Jose ADU cost guide is the closest apples-to-apples comparison I can point you to, and the Data Hub is where I’d look next for the most current bid ranges on both.