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 Woodside
A home addition or ADU in Woodside typically runs $45,000-$130,000 for room additions and $90,000-$220,000 for detached ADUs, with the real calendar driver being Town permits, not construction labor. We’re Rowan Construction Group Redwood City, and we coordinate dispatch and scheduling from our San Francisco Bay Area office with crews serving Woodside directly. We’ve learned that in this town, the contractor who budgets 4-8 weeks for oak-tree permitting and Design Review Board review before ordering custom millwork is the contractor who delivers on the date promised. Call (650) 560-7228 to schedule your free estimate, and we’ll walk your property with the permit timeline in hand.
Why Rowan Construction Group Redwood City Is Woodside’s Preferred Home Additions & ADU Company
We’ve completed additions and ADUs across Woodside’s hillside estates, from mid-century ranches near the Skyline Boulevard corridor to contemporary builds closer to the Town Center. Our Home Additions & ADU in Woodside portfolio includes projects where we phased construction around active equestrian facilities, coordinated with arborists on protected-oak drip lines, and delivered documented photo records at every site visit.
Woodside customers find us through referrals from architects and interior designers who’ve seen our work hold to the written price. Our 365-Day Done Right Promise is printed on every contract, backed by The Haven Standard terms page, not an asterisk. Under Clause 1, the price is written before anyone starts. Under Clause 4, no change proceeds without a signed change order. That discipline is why our projects finish within a few percent of the agreed number across 4,000-plus jobs since 2007.
Calls are answered by a live person 24/7. Crews are background-checked and uniformed. Every visit includes a documented photo record as standard, not an upgrade. And we offer a Free Second Opinion on any written estimate - bring a competitor’s quote and we’ll review it line by line at no charge.
Our Home Additions & ADU Services in Woodside
ADU Design & Permitting
ADU design and permitting in Woodside is where most projects live or die on the calendar. The Town’s protected-oak ordinance requires a permit and certified arborist report for any ground disturbance within the drip line of a native coast live oak, which affects utility trenching, foundation excavation, and drainage installation on virtually every parcel. Add Design Review Board approval and, for properties near the Crystal Springs corridor, Alquist-Priolo seismic engineering, and even a modest ADU can face months of pre-construction review. Our Home Additions & ADU team runs permit applications in parallel with design development, so when the Town signs off, we’re ready to break ground the following week. We quote a flat price with a written scope and a written warranty; “call for a quote” is not an option here.
Garage Conversion ADU
A garage conversion ADU in Woodside runs $30,000-$80,000 and appeals to homeowners who want rental income or family housing without disturbing the main estate’s footprint. The catch: many Woodside garages sit under oaks or on sloped grades that trigger the same arborist and seismic reviews as new construction. We assess the existing slab, roof structure, and utility capacity before quoting, then fix the price in writing. If the garage shares a foundation with the main house, we engineer the separation to current code, including fire-rated assemblies and independent utility meters where required.
New Detached ADU
New detached ADUs in Woodside range from $90,000-$220,000 and offer the most design flexibility - but also the most regulatory exposure. On the western, uphill side of Woodside against the Santa Cruz Mountains, steep grades and heavier rainfall demand engineered retaining walls, French drains, and slope-stability plans that go well beyond what valley-floor projects in Menlo Park or Atherton require. We coordinate the architect, structural engineer, and interior designer on custom millwork, architectural glass, and specialty finishes, then lock the scope and allowances in writing before any long-lead order is released. Lead times, not labor, set the calendar on this tier.
Junior ADU & Interior Conversion
Junior ADUs and interior conversions in Woodside convert existing square footage - a basement, a portion of the main house, or an attached wing - into independent living units. These avoid some site-work triggers but still face Town review if the work involves exterior openings, utility upgrades, or structural modifications. We evaluate the existing framing, insulation, and egress paths, then quote a flat price with a written scope. For properties with equestrian infrastructure, interior conversions can preserve barns, paddocks, and covered arenas that a detached build might disrupt.
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.
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AfterTrusted Brands We Service in Woodside
We source across fifty-plus vetted brands, giving our written quotes honest numbers rather than inflated ones. For Woodside’s high-end additions and ADUs, we regularly specify Cambria and Caesarstone countertops, Kohler and Toto fixtures, and KraftMaid and Wellborn cabinets, and we also handle Bathroom Remodeling in Woodside with the same material standards. On window and door packages, we work with CGI, CWS, and ES Windows for performance glazing that meets California’s Title 24 requirements while handling Woodside’s fog-heavy western exposure. We don’t markup long-lead items; the allowance in your written quote is the price we pay, documented on invoice. That transparency is Clause 1 of The Haven Standard.
Common Home Additions & ADU Problems We See in Woodside Homes
- Ordering custom cabinetry, architectural glass, or specialty finishes before Town permits clear. We’ve seen contractors release $40,000 millwork orders while the Design Review Board is still reviewing massing and materials, only to face months of storage fees or specification changes when the permit arrives. We fix the scope in writing, then order - never before.
- Ignoring the protected-oak drip line during site planning. A contractor who trenches for utilities or excavates for a foundation without checking the arborist report can trigger an unpermitted ground disturbance that stalls inspection sign-off mid-project. We flag every oak on the survey before staking, and we budget the 4-8 week review into the master schedule.
- Treating a hillside addition like a valley-floor job. Woodside’s western slopes require engineered retaining walls, slope-stability analysis, and seismic detailing for the Alquist-Priolo zone. Skip any of these and you’ll see failed inspections and change orders after the subfloor is framed. We engineer for the site, not the neighborhood average.
- Verbal “favors” that become scope creep. When a designer swaps Caesarstone for Silestone after rough-in, that becomes a written change order against the draw schedule - not a verbal accommodation that balloons the final invoice. Our customers know the price at every phase because it’s documented, not assumed.
Pricing for Home Additions & ADU in Woodside, CA
Here’s what honest pricing looks like for Woodside’s market. These are flat-price ranges with written scope and warranty, delivered before any work starts:
| Service | Price Range in Woodside |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion ADU | $30,000 - $80,000 |
| Cabinet Installation | $4,000 - $13,000 |
| Countertop Installation | $2,000 - $6,500 |
What moves the number? Hillside grading and retaining walls on the western slope. Arborist reports and oak-tree permits. Alquist-Priolo seismic engineering along the Crystal Springs corridor. Custom millwork and architectural glass with 12-16 week lead times. We itemize these in the written quote, so you know what’s allowance, what’s fixed, and what triggers a change order if you modify the spec. Call (650) 560-7228 for an exact quote - estimates are free, and we deliver a written price before anyone picks up a tool.
We Also Serve Cities Near Woodside
Our crews work throughout the San Francisco Bay Area, including Woodside and neighboring Redwood City, San Carlos, Menlo Park, and Belmont. Each city carries its own permit environment and site conditions; we adjust the written scope and schedule accordingly, never copy-paste from one jurisdiction to another.
Serving Woodside, CA - Our Local Coverage Area
We’re based in the Woodside 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 Woodside
Lead times on long-lead items - custom cabinetry, architectural glass, specialty finishes - plus Town permit review, set the calendar, not construction labor. The price is fixed because we lock the scope of work and allowances in writing before any order is released, and no change proceeds without a signed change order. Call (650) 560-7228 for a written quote you can screenshot and compare.
Yes. Woodside’s protected-oak ordinance requires a Town permit and certified arborist report for any ground disturbance within the drip line of a native coast live oak, covering utility trenching, foundation excavation, and drainage work. The review takes 4-8 weeks, and skipping it can stall inspection sign-off mid-project. Call (650) 560-7228 and we’ll walk your property to identify every oak that affects the build.
Properties on the western, uphill side against the Santa Cruz Mountains face substantially more rainfall and prolonged fog than the valley floor, and steep grades make slope instability and landslide risk a genuine engineering concern. The Alquist-Priolo zone along the Crystal Springs corridor requires seismic engineering that valley-floor projects don’t. We engineer retaining walls, French drains, and grading plans for these conditions, and we itemize that cost in the written quote. Call (650) 560-7228 for a site-specific assessment.
Yes, with phased grading and trenching that keeps barns, paddocks, and covered arenas in use. On a mid-century ranch along the western uphill side of Woodside, we added a second-story primary suite and a detached ADU while the owners maintained their equestrian facilities, phasing work around the oak drip line with an arborist on site. The key is a master schedule that sequences site work, utility rough-in, and foundation work around daily barn operations. Call (650) 560-7228 and we’ll design a phasing plan with your property’s use in mind.
A garage conversion ADU ($30,000-$80,000) reuses an existing structure and footprint, which can reduce site-work triggers but still requires Town review for structural separation, utility upgrades, and fire-rated assemblies. A new detached ADU ($90,000-$220,000) starts from bare ground, offering design flexibility but full exposure to oak-tree permits, Design Review Board approval, and hillside engineering. The right choice depends on your property’s oak coverage, grade, and existing garage condition. Call (650) 560-7228 for a free evaluation.
Ready to price your project? Call (650) 560-7228 to schedule your free estimate. We’ll deliver a written price with a written scope and warranty before any work starts, and we’ll flag every permit and lead-time issue that affects your calendar. That’s The Haven Standard. It’s been our practice since 2007.
Written by Grant Rowan, Owner at Rowan Construction Group, serving Woodside since 2007.