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 detached ADU or second-story addition in Los Gatos typically runs $45,000-$130,000 for room additions and $90,000-$220,000 for full ADU construction, with most projects taking 4-8 months from permit to final inspection. We’re Rowan Construction Group, and our crews work Los Gatos from the valley floor ranches near Highway 9 up through the hillside neighborhoods above downtown. Calls route to a live person 24/7, and we dispatch from our San Francisco Bay Area office with crews that know the Town’s permitting rhythms, the Cal Fire hazard zones, and the parking realities on streets like Tait Avenue or University Avenue where staging space is tight. Call (669) 202-9618 to schedule your free estimate.
Why Rowan Construction Group Cupertino Is Los Gatos’s Preferred Home Additions & ADU Company
We’ve delivered written quotes on over 4,000 projects since 2007, and a growing share of those have come from Los Gatos homeowners adding square footage without leaving the school district or the downtown walkability they bought for. Our three-star reviews get read, and we leave them up, because they show the full picture, not a curated one.
Response time to Los Gatos is same-day for initial calls and typically 48-72 hours for an on-site walkthrough, depending on hillside access and whether the property sits inside a Cal Fire Very High Fire Hazard Severity Zone that requires a preliminary hazard assessment. We know the difference between a flat-lot ranch near Los Gatos High and a stepped-caisson hillside home off Bella Vista Drive, and that difference changes the foundation assumptions in your quote.
Our documented photo record comes standard on every visit, not as an upgrade. You get timestamped images of existing conditions, rough-in progress, and final finish work, plus the written scope and flat price before any work starts. Under Clause 1 of The Haven Standard, the number is in writing before anyone picks up a tool.
Our Home Additions & ADU Services in Los Gatos
ADU Design & Permitting
ADU design and permitting in Los Gatos is where projects live or die before ground breaks. The Town runs its own architectural review board with a reputation among local contractors for granular scrutiny, especially on hillside parcels. Roof pitch, exterior materials, grading cut-and-fill limits, and view-impairment assessments can each trigger separate review cycles that add months to a timeline. We front-load this research, submitting a complete package with engineered drainage plans and, where required, Chapter 7A ignition-resistant assembly specifications. Our permit package includes the written price, the written scope, and a realistic draw schedule that accounts for Town review timelines, not the faster unincorporated Santa Clara County process some contractors mistakenly assume.
Garage Conversion ADU
Garage conversions in Los Gatos range $30,000-$80,000 and work best on the valley floor’s mid-century ranches where the garage sits at grade with standard footings. Hillside garages are a different animal, often built on fill or stepped foundations that weren’t designed for residential occupancy loads. We assess the existing slab, the bearing capacity, and the fire separation between the new living space and any remaining garage function before we quote. In Cal Fire zones, the conversion may need ignition-resistant exterior upgrades even if the structure itself isn’t new.
New Detached ADU
New detached ADUs are our most requested addition type in Los Gatos, typically $90,000-$220,000 depending on size, utility trenching distance, and hillside complexity. We built a detached ADU on a steep, individually graded lot in the Los Gatos hills above downtown, where the existing 1960s home sat on stepped caisson foundations and the site fell inside a Cal Fire Very High Fire Hazard Severity Zone. Our tech had to set a Class A roof assembly with ignition-resistant siding and decking, engineer a drainage plan that captured concentrated runoff, and coordinate a party-wall notice with the neighbor because the new structure came within a few feet of the property line. After a rough-in inspection and final sign-off, the client had a permitted ADU that passed both seismic and WUI review, and we handed over a punch list with everything in writing.
Junior ADU & Interior Conversion
Junior ADUs, or JADUs, convert existing interior space within the primary residence, often a bedroom or attached garage area, with a separate exterior entrance. In Los Gatos’s older downtown core, Victorian and Craftsman homes from the late 1800s and early 1900s can yield surprising JADU opportunities, but also surprises: unpermitted prior work, outdated electrical, or foundation settling that shows up when you open walls. We document existing conditions with our standard photo record before demolition, so there’s evidence of what we found, not just what we fixed.
Room Additions
Single-room additions on Los Gatos lots require careful staging planning. Narrow streets in neighborhoods near the downtown corridor mean delivery trucks need coordinated timing, and neighbor notification is often practical before it’s procedural. We map material delivery windows, dumpster placement, and crew parking as part of the written scope, because a blocked street or 7 a.m. noise complaint can shut down a job faster than a failed inspection.
Second Story Additions
Second-story additions are common on the valley floor ranches where the original 1,200-square-foot footprint no longer fits the household. The existing foundation and framing must be verified for vertical load capacity, and in Los Gatos’s hillside zones, the added height may trigger view-impairment review from the architectural review board. We engineer for the load, coordinate the structural inspection sequence, and price the foundation upgrade if one is needed, not as a change order surprise.
ADU Site Prep & Utilities
Utility trenching on Los Gatos hillside lots often runs longer and deeper than flat-site estimates predict. Steep terrain concentrates rainfall runoff, and the Town enforces strict grading ordinances requiring engineered drainage plans even for modest additions. Our quotes include the trench length, the sewer lateral connection, and the drainage design as line items, not buried contingencies.
What happens when you call
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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.
Before
AfterTrusted Brands We Service in Los Gatos
We source across fifty-plus vetted brands, giving the written quote honest numbers rather than inflated ones. For Los Gatos ADU and addition kitchens, that means KraftMaid and Wellborn cabinet lines with documented lead times, and Cambria or Silestone quartz surfaces with slab-yard availability confirmed before we write the price. We don’t quote brands we can’t source reliably, because a delayed cabinet delivery blows a draw schedule as surely as a permit delay does. Our crews carry common hardware and fastener stock for these lines, so finish carpentry doesn’t wait on a parts run.
Common Home Additions & ADU Problems We See in Los Gatos Homes
- Underscoping the architectural review board timeline. Roof pitch, exterior materials, grading cut-and-fill limits, and view-impairment assessments can each trigger separate review cycles. Contractors who estimate Los Gatos permitting on a Santa Clara County unincorporated timeline routinely blow client schedules and budgets before excavation starts.
- Ignoring Cal Fire Chapter 7A requirements on hillside additions. Ignition-resistant assemblies for roofing, siding, vents, and decks are mandatory on new builds and major additions in Very High Fire Hazard Severity Zones, not optional upgrades. We specify these in the original quote, not as a mid-project change order.
- Treating steep hillside lots like flat-valley parcels. Caissons, deepened piers, and stepped footings surface mid-project when a contractor hasn’t done the geotechnical homework. Our hillside quotes include a soils assessment contingency and a clear protocol for what happens if we hit non-standard foundation conditions.
- Failing to plan staging and parking on narrow Los Gatos streets. Delivery delays, neighbor complaints, and potential work-hour or noise ordinance violations follow quickly. We map staging, coordinate delivery windows, and notify adjacent properties as part of pre-construction, not as damage control.
Pricing for Home Additions & ADU in Los Gatos, CA
Our written prices before any work starts are flat, with line-item scope and a written warranty. Below are the ranges we see in the Los Gatos market, calibrated for the dual seismic-plus-wildfire compliance burden and the Town’s extended permitting timeline that this market carries.
| Service | Typical Range in Los Gatos |
|---|---|
| Home Addition | $45,000-$130,000 |
| ADU Construction | $90,000-$220,000 |
| Garage Conversion | $30,000-$80,000 |
| ADU Design & Permitting | Included in construction quote |
| Room Additions | Quoted per scope |
| Second Story Additions | Quoted per scope |
What moves the number: hillside versus flat lot, foundation conditions, Cal Fire zone requirements, utility trenching distance, and the Town’s current architectural review queue. We don’t write a price until we’ve walked the site and reviewed the preliminary title report for easements or setback issues. Bring a competitor’s written estimate and we’ll review it line by line at no charge. Call (669) 202-9618 for your free estimate.
We Also Serve Cities Near Los Gatos
Our crews work throughout the South Bay, including Los Gatos and neighboring Saratoga, Campbell, Cupertino, and Santa Clara. Each city carries its own permitting landscape, fire hazard designations, and hillside conditions, and our quotes reflect those specifics rather than a regional average. If you’re comparing options across city lines, we’ll walk each property and write a price that accounts for the actual jurisdiction and site conditions.
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
Yes, you should notify adjacent property owners before construction begins, and for structures near property lines, a formal party-wall notice or easement verification may be required by the Town or by practical necessity. On tight Los Gatos lots where setbacks are minimal, we coordinate neighbor notification as part of pre-construction planning, including work-hour schedules and staging locations that minimize impact. Call (669) 202-9618 and we’ll review your survey and title report to flag any party-wall or access issues before permitting.
The architectural review board adds separate review cycles for roof pitch, exterior materials, grading cut-and-fill limits, and view-impairment assessments that flat-valley cities do not impose. This can extend the permitting timeline by months compared to Campbell or Santa Clara. We front-load our submittal package with complete architectural, structural, and landscape documentation to minimize back-and-forth, and we price the project with a realistic schedule that accounts for these reviews.
Chapter 7A of the California Building Code mandates ignition-resistant construction assemblies for roofing, siding, vents, and decks on new builds and major additions in these zones. Class A roof coverings, ember-resistant venting, and non-combustible decking materials are required, not optional. We specify these materials in our original written quote and coordinate the Cal Fire compliance inspection as part of the standard inspection sequence, not as an afterthought.
We map material delivery windows, dumpster placement, and crew vehicle parking before work starts, coordinating with the Town’s work-hour and noise ordinances and notifying adjacent properties of the schedule. On narrow streets near downtown or in hillside neighborhoods with limited shoulder, we may stage materials in a consolidated delivery or use smaller equipment that fits the access constraints. The plan is written into the scope, not improvised daily.
Often yes, because the 1960s-1980s custom hillside homes common in Los Gatos were built on caissons, deepened piers, or stepped footings designed for the original structure’s load, not for added square footage or a second story. We include a geotechnical assessment contingency in hillside quotes and specify the protocol for foundation verification before vertical construction begins. If upgrades are needed, the change order is written and signed before work proceeds, keeping the final cost within a few percent of the agreed price.
Written by Grant Rowan, Owner at Rowan Construction Group, serving Los Gatos since 2007.