Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across Los Gatos
A typical home addition or ADU in Los Gatos costs $45,000-$130,000 for attached work and $90,000-$220,000 for detached ADU construction, with the Town’s architectural review adding 4-8 weeks to the front of every schedule. Our crews serve Los Gatos from our San Francisco Bay Area dispatch office, and we’ve learned that local expertise here means planning around the review board before a single 2×4 is cut. Call (650) 446-9092 to schedule your free estimate with a written line-item price.
Why Rowan Construction Group Palo Alto Is Los Gatos’s Preferred Home Additions & ADU Company
We’ve delivered projects across the valley floor and into the hillside neighborhoods above Highway 17, from the historic downtown core to the cut-and-fill lots along Belgatos and Kennedy Road. Los Gatos homeowners leave reviews that mention the same thing: we put the number in writing before anyone picks up a tool, and we don’t start work until the architectural review is complete.
Our response time to Los Gatos is same-day or next-day for initial consultations, and we schedule those consultations to include a preliminary review timeline so you know what the Town’s process will mean for your calendar. The crews are background-checked and uniformed; a live person answers calls 24/7; and every visit includes a documented photo record as standard.
What separates our work in Los Gatos is familiarity with the dual overlay of seismic and WUI requirements that flatland cities like Campbell don’t face. We know which hillside parcels fall within the High Fire Hazard Severity Zone, where Class A roofing and ignition-resistant cladding are mandatory, and we price those materials into the written quote from day one under Clause 1 of the Haven Standard.
Our Home Additions & ADU Services in Los Gatos
ADU Design & Permitting
ADU design and permitting in Los Gatos starts with the architectural review packet, not the building permit. We prepare the materials package - stucco samples, roof pitch diagrams, color boards, and elevation renderings - and file it with the Town before construction drawings are finalized. A typical detached ADU in Los Gatos runs $90,000-$220,000, including the structural engineering required for hillside sites. We use the review window to order long-lead materials and coordinate utility tie-ins so the calendar keeps moving.
Garage Conversion ADU
Garage conversions in Los Gatos cost $30,000-$80,000, but the real variable is the slab. Many 1950s-70s valley-floor garages have settled or cracked slabs that need replacement before the space can be conditioned, and hillside garages on fill often need structural remediation. We inspect the slab, the fire separation between dwelling and garage, and the ceiling height against ADU code requirements during the first visit, then write the scope and price before you sign.
New Detached ADU
A new detached ADU in Los Gatos faces the strictest architectural review of any project type - the Town scrutinizes height, roof form, and materials compatibility with the primary residence. We design to those preferences from the first sketch: matching roof pitch, compatible siding, and colors drawn from the existing palette. The $90,000-$220,000 range includes foundation, framing, MEP, and finishes; hillside sites with retaining walls or utility trenching fall toward the upper end.
Junior ADU & Interior Conversion
Junior ADUs - conversions within the existing footprint, often with a kitchenette and separate entrance - are the fastest path to rental income in Los Gatos, but they’re not exempt from review. We were brought in to convert an attached garage into a Junior ADU on a 1960s ranch on Belgatos Road, where the original slab was already showing settlement from the hillside fill. The house was within the Town’s review jurisdiction, so we submitted a materials package with matching stucco and a low-pitched roof to match the existing profile, pulled the permits, and used the review window to demo and rough-in the new bathroom and kitchenette so the drywall and finishes could start the moment sign-off came through. The result was a punch-list-ready ADU that passed inspection without a single change order tied to review comments.
Second Story Additions
Second story additions in Los Gatos trigger both architectural review and structural scrutiny, especially on older homes with unreinforced masonry chimneys or soft-story conditions. The $45,000-$130,000 range for general additions expands significantly for second-story work due to foundation upgrades, seismic retrofit, and potential WUI compliance on hillside parcels. We bring a structural engineer to the first site visit and include their findings in the written quote.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
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Our material selections for Los Gatos projects are driven by what passes architectural review and what performs in the local climate. For hardscape and site work on hillside ADU builds, we specify Belgard and Techo-Bloc pavers for retaining walls and walkways - both brands carry WUI-compliant surface options and integrate with engineered drainage systems that handle the wet-season saturation common above Highway 17. Cambria and Caesarstone countertops appear regularly in our ADU kitchens; their quartz composition holds up to the temperature swings of unconditioned utility spaces during construction. We stock local supplier relationships for these brands so replacement or add-on orders don’t stall a job that’s already moving through review.
Common Home Additions & ADU Problems We See in Los Gatos Homes
- Review delays from incompatible design. Submitting a design packet that ignores the Town’s architectural review preferences - heights, roof pitch, and materials that read as compatible with the existing structure - sends the project back for re-review and stalls the calendar. We match the existing profile from the first submission.
- Construction scheduled before approval. Treating the build as construction-first and review-second means the crew stands around with a rough-in permit in hand but no approved design to build toward, and the job sits half-finished waiting on a committee. We don’t schedule demo until the review packet is signed off.
- Unplanned seismic and structural scope. Missing the seismic and WUI overlays that apply in Los Gatos - unreinforced masonry chimneys, soft-story conditions, or hillside fill settlement - adds scope the owner didn’t plan for when permits are pulled. We identify these conditions during the initial site visit and write them into the quote.
- Hillside foundation movement on cut-and-fill lots. The cut-and-fill lots developed in the 1960s-70s in hillside neighborhoods above Highway 17 and along the Belgatos and Kennedy Road corridors are well known locally for retaining wall failures and foundation settlement as engineered fill slowly consolidates. We inspect for this pattern and include remediation in the written scope when it’s present.
Pricing for Home Additions & ADU in Los Gatos, CA
These are the ranges we write into quotes for Los Gatos projects, based on 4,000-plus jobs since 2007. Every number is a flat price with a written scope and a written warranty; no work proceeds without that document signed.
| Project Type | Typical Range in Los Gatos |
|---|---|
| Home Addition (attached) | $45,000-$130,000 |
| ADU Construction (detached) | $90,000-$220,000 |
| Garage Conversion ADU | $30,000-$80,000 |
What moves a project within these ranges: hillside vs. valley-floor site, structural upgrades required by permit, WUI-compliant material specifications, and the extent of utility trenching or sewer connection. A flatland garage conversion with good slab condition and nearby sewer tie-in falls toward $30,000; a detached ADU on a cut-and-fill hillside with retaining wall replacement, engineered foundation, and Class A roof assembly falls toward $220,000. We deliver the written price before any work starts, every time, and no change proceeds without a signed change order - the discipline that has kept our projects within a few percent of the agreed cost across 4,000-plus jobs.
Call (650) 446-9092 for an exact quote on your project. Estimates are free, and we offer a Free Second Opinion on any written estimate you’ve already received - we’ll review it line by line at no charge.
We Also Serve Cities Near Los Gatos
Our crews work throughout the South Bay, including Home Additions & ADU in Los Gatos and neighboring Campbell, Cupertino, Santa Clara, and Sunnyvale. Each city has its own permit timeline and design requirements; we adjust the submittal packet and schedule accordingly. If you’re near the Los Gatos border and unsure which jurisdiction applies, call us and we’ll verify it during the first call.
Serving Los Gatos, CA - Our Local Coverage Area
We’re based in the Los Gatos area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Home Additions & ADU in Los Gatos
The Town of Los Gatos architectural review typically adds 4-8 weeks to the front of the schedule, depending on completeness of the initial submittal and whether the project requires a hearing. We build this timeline into the plan from day one and use the review window to order materials and coordinate utility work so no construction days are lost. Call (650) 446-9092 to schedule your free estimate and we’ll outline the specific timeline for your property.
The review board favors roof pitches, siding materials, and color palettes that read as continuous with the existing structure - matching stucco texture, compatible trim profiles, and roof forms that don’t exceed the height or mass of the primary dwelling. We prepare the materials package to these preferences from the first sketch, which is why our resubmission rate is low. Call (650) 446-9092 and we’ll show you examples from recent approvals in your neighborhood.
Yes, if your home was built before 1980 and has unreinforced masonry chimneys, soft-story conditions, or a raised foundation without adequate shear walls, the building permit will trigger mandatory seismic upgrades when the ADU permit is pulled. We identify these conditions during the initial site visit and include the structural work in the written quote. Call (650) 446-9092 for a free assessment of your specific property.
We sequence the job so that demo, rough-in, and material procurement happen during the review window, with the finish trades scheduled for the week after sign-off. This means the crew is never standing idle waiting for a committee decision, and the owner isn’t paying for labor days with no approved design to build toward. Call (650) 446-9092 and we’ll walk you through the specific sequence for your project type.
Hillside additions in Los Gatos fall within California’s High and Very High Fire Hazard Severity Zones, mandating WUI-compliant construction - Class A roofing, ember-resistant venting, and ignition-resistant cladding - plus engineered foundations and retaining walls to address the settlement and soil movement common on cut-and-fill lots. The steep terrain also complicates material delivery and crew access, which we factor into the written schedule and price. Call (650) 446-9092 for an exact quote that includes these hillside-specific requirements.
Ready to start your Los Gatos addition or ADU? Call (650) 446-9092 to schedule your free estimate. You’ll receive a written flat price with a written scope and warranty before any work begins - that’s Clause 1 of the Haven Standard, and it’s how we’ve kept projects within a few percent of the agreed cost since 2007. Ask about our 365-Day Done Right Promise and our Free Second Opinion on any written estimate you’ve already received.
Written by Grant Rowan, Owner at Rowan Construction Group, serving Los Gatos since 2007.