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 Redwood Shores
Home additions and ADU construction in Redwood Shores almost always runs between $45,000 and $130,000 for a room addition, and $90,000 to $220,000 for a ground-up detached ADU. Those are real numbers for this specific market, not a national average. Redwood Shores lots sit on reclaimed Bay mud, which changes how footings get engineered, how groundwater gets managed, and what the HOA will sign off on before you ever see a backhoe. If you’re weighing a garage conversion, a second story, or a detached unit off Mariner Drive or along Bridge Parkway, call us at (877) 610-1318 for a free estimate. We know exactly what these jobs take in 94065, because we’ve built them here.
Why Barrett & Sons Construction Is Redwood Shores’s Preferred Home Additions & ADU Company
We’re Barrett & Sons Construction, founded in 1998 and still owner-operated by Tom Barrett. Tom’s sons run crews on Redwood Shores job sites most days. When you call, a live person answers – not a voicemail box, not a call center in another state. That matters more than most people realize when an HOA architectural review stalls and you need straight answers about a pile cap survey or a dewatering plan.
Our Redwood Shores customers deal with the same reality on nearly every project: the ground underneath this community is not like anything in Belmont or San Carlos. It’s dredged fill over Bay mud, and it demands an engineer who has worked with piles, not just slabs. We have. We’ve also sat through enough Redwood Shores HOA reviews to know what triggers a stall: stucco color mismatches, lagoon setback questions, and foundation specs that don’t account for differential settlement. Our Home Additions & ADU team handles those conversations before they become delays.
Our 90-Day Done Right Promise is written on every contract. If something isn’t right after we finish, one call brings Tom back. That holds whether we’ve built a 400-square-foot junior ADU or a full second-story addition. And because every scope change arrives as a written change order before work proceeds, the bill you sign is the bill you pay.
For 29 years, we’ve built our name the slow way – one street, one permit, one signed inspection at a time. Ask anyone on Shorebird Drive or Sandpiper Lane, or look up Tom’s license number yourself. We publish it because we stand behind it.
Our Home Additions & ADU Services in Redwood Shores
ADU Design & Permitting
In Redwood Shores, ADU design and permitting is not a paper exercise. It’s a coordination job involving San Mateo County building codes, your HOA architectural review board, and a soils engineer who understands the pile-supported reality of 94065. We handle the full design package, submit for HOA review, and pull permits. We also write the scope in writing before any work starts, including allowances and change-order terms. That’s how a job avoids the surprise invoice at the end.
Garage Conversion ADU
Garage conversions in Redwood Shores typically run $30,000 to $80,000, and they’re popular for good reason – the footprint already exists, and the foundation is usually intact. But cutting into an original stucco wall or running new utility lines can void builder warranties if the HOA rules and original waterproofing aren’t respected. We document the original condition, get the right sign-offs, and protect the rest of the house while the garage becomes a legal dwelling unit.
New Detached ADU
A ground-up detached ADU in Redwood Shores runs $90,000 to $220,000. The wide range reflects site conditions more than size. On a lagoon-front lot, groundwater can sit just 2 to 3 feet below grade. Dewatering, pile driving, and engineered footings are non-negotiable – and they’re exactly the line items that less experienced contractors underbid. We install dewatering systems before we pour, not after the excavation floods. And we bring in the helical or driven pile contractor who has already worked behind the lagoons, not someone who’ll learn on your lot.
Junior ADU & Interior Conversion
A junior ADU – often a converted primary bedroom suite with a kitchenette and separate entry – is one of the more cost-effective ways to add rental income inside an existing Redwood Shores home. Because it stays within the original building envelope, HOA scrutiny is usually lighter. But plumbing, sound separation, and egress still need permits, and they still need to respect the existing pile cap layout. We design these to fit the house as it was built, not as the marketing brochure imagined it.
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.
Trusted Brands We Service in Redwood Shores
For the finishes and systems in Redwood Shores additions and ADUs, we carry brands you can look up and verify. Schluter for waterproofing in showers and wet areas, especially important near the Bay where moisture never really leaves. GAF roofing materials on additions where the original roof has already been replaced once or twice. Grohe fixtures in ADU kitchens and baths. When a Redwood Shores customer asks for a specific brand, we can usually have it on site within a week, sourced through our Bay Area suppliers. No mystery materials off a van.
Common Home Additions & ADU Problems We See in Redwood Shores Homes
- Groundwater at 2-3 feet during excavation. Nearly every ADU footing or utility trench in Redwood Shores hits water fast. Contractors without local experience flood the hole, lose days, and hand the owner a schedule overrun. We plan dewatering before we put a shovel in the ground.
- HOA architectural review stalls. Adding a detached ADU or even a sunroom triggers architectural review in most Redwood Shores HOAs. Stucco match, lagoon setback, and roof pitch are the usual sticking points. We submit drawings that answer those questions up front.
- Voided builder warranties. Master-planned phases built in the early 2000s may still carry builder warranty terms on original waterproofing and stucco. Cutting into those surfaces without reviewing the warranty and HOA rules can nullify coverage. We review that paperwork before we make the first cut.
- Differential settlement from ignored pile caps. A second-story addition adds load. If new footings don’t respect the existing piles, the original structure can crack. On lagoon-adjacent lots in 94065, this isn’t a theoretical concern. We survey the pile cap layout before we design the addition.
Pricing for Home Additions & ADU in Redwood Shores, CA
Here’s what we tell Redwood Shores homeowners when they ask about cost. A home addition typically runs $45,000 to $130,000. A garage conversion runs $30,000 to $80,000. A full new detached ADU runs $90,000 to $220,000. What drives the range is site-specific: lagoon proximity, groundwater depth, HOA conditions, and how much of the original pile foundation can be reused.
| Project | Redwood Shores Price Range |
|---|---|
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion ADU | $30,000 - $80,000 |
| Home Addition | $45,000 - $130,000 |
Every estimate from Barrett & Sons is free and written. Every allowance is on paper. Every change order arrives in writing before work changes. We also honor a permanent 10% Senior & Veteran discount. Call (877) 610-1318 to schedule your free estimate – no trip charge inside San Mateo County.
We Also Serve Cities Near Redwood Shores
Our crews work up and down the Bay shoreline, and we regularly take projects in Foster City, Belmont, San Carlos, and San Mateo. The foundation and HOA conditions change from city to city, but the approach stays the same: permits pulled, written change orders, and one owner accountable. If you’re in Redwood Shores or the surrounding area, we’re your Home Additions & ADU in Redwood Shores team and we’d like to take a look at your lot.
Serving Redwood Shores, CA - Our Local Coverage Area
We’re based in the Redwood Shores 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 Redwood Shores
Yes – every single Redwood Shores HOA we’ve worked with requires architectural review for a detached ADU, even when the stucco color and texture match perfectly. The review covers setbacks from the lagoons, rooflines, drainage, and sometimes the site plan for construction parking. We submit the package before construction and get written approval before moving dirt.
You don’t avoid it – you plan for it. Groundwater in Redwood Shores often sits at 2 to 3 feet below grade, especially near the lagoons. We install a dewatering system before reaching that depth, then keep it running through the excavation and pile work. Anyone who tells you they’ll “see how it goes” hasn’t dug in 94065.
Yes, in most cases. A garage conversion usually stays within the existing building footprint, so the original piles aren’t bearing meaningfully more load than they already do. The key is not cutting into stucco or waterproofing at the garage-to-house junction without a clear plan. We map that junction early and preserve the original building envelope.
It can, if you cut into original waterproofing, stucco, or load-bearing elements without reviewing the warranty language and HOA rules. Some phases built in the early 2000s still carry warranty terms on specific systems. We review that paperwork with you before design begins, and we can often phase the work to protect the remaining coverage. Call (877) 610-1318 and we’ll walk through it together.
Because Redwood Shores sits on reclaimed Bay mud with deep pile foundations, not on solid upland soil. That means engineered pile-supported footings, dewatering systems, stricter HOA reviews, and sometimes lagoon setback compliance. Redwood City lots on solid ground simply don’t carry those costs. It’s not markup – it’s geology. Get an exact written quote for your lot; estimates are free.
Call Barrett & Sons Construction at (877) 610-1318 to schedule your free estimate for a home addition or ADU in Redwood Shores. Tom Barrett will be on the phone or on your lot – not a sales team. We’ll scope it in writing, price it honestly, and build it so the HOA is happy and the inspector signs off.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Redwood Shores and the Bay Area since 1998.