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 ADUs in Redwood Shores, CA typically run between $45,000 and $130,000 for a room addition and $90,000 to $220,000 for a detached ADU, with garage conversions landing in the $30,000 to $80,000 range. Those are real numbers for this specific market, not Peninsula-wide averages. Redwood Shores is unlike any other city on the Bay shoreline, and the work here carries different engineering, HOA, and groundwater realities than neighboring Foster City or San Mateo. We know this because we’ve framed additions, dug footings, and pulled permits on lagoon-front lots across the 94065 ZIP for years. Call (877) 610-1318 and we’ll give you an honest read on your lot before you commit to anything.
Why Barrett & Sons Construction Is Redwood Shores’s Preferred Home Additions & ADU Company
Barrett & Sons Construction is owner-operated, founded by Tom Barrett in 1998, and his sons run the crews. That matters in Redwood Shores because this is a community where the same generation of homes, built between the late 1970s and early 2000s, is reaching the age where additions and ADUs make real financial sense. We have walked dozens of these stucco and frame homes, and we understand the pile foundations, the HOA architectural boards, and the groundwater table that define construction here.
Homeowners in Redwood Shores have watched national outfits quote one number on the phone and show up with another. We do not work that way. Every scope, every allowance, and every price change arrives as a written change order before a single nail moves. Every eligible job gets permits pulled and inspections signed. Tom Barrett publishes his name, his address, and his license number. Look it up before you sign anything.
Calls to (877) 610-1318 are answered by a live person, 24/7. Not a voicemail box. Not an out-of-state call center. When you call about a possible garage conversion or second-story addition in Redwood Shores, you talk to someone who knows the difference between a pile cap and a spread footing and why that difference decides whether your project gets approved.
Our Home Additions & ADU Services in Redwood Shores
ADU Design & Permitting
An ADU in Redwood Shores starts with two layers of approval: the City of Redwood City’s building department (Redwood Shores is part of Redwood City) and your HOA’s architectural review board. We handle both. Our team prepares the drawings, submits the plans, walks them through HOA design review, and manages the permit process through final inspection. For a 94065 property, that almost always means documenting existing pile cap locations and preparing a soils report before the city will even look at the foundation plan. We include that in the scope from day one, not as a surprise add-on.
Garage Conversion ADU
Garage conversions in Redwood Shores typically run $30,000 to $80,000 depending on whether you’re converting an attached two-car garage in a single-family home or working within a townhome complex where the HOA restricts exterior changes. The good news: many Redwood Shores garages sit on the same slab and pile system as the main structure, so conversion is structurally straightforward. The catch: HOA parking minimums usually mean you’ll need to add a covered carport or designated space elsewhere on the lot. We factor that into the plan before you spend a dime.
New Detached ADU
Building a new detached ADU in Redwood Shores means new foundation work, and that is where local knowledge saves you real money. The reclaimed Bay mud under nearly every lot in this city compresses unevenly. A new ADU foundation needs pile support or a mat slab engineered for differential settlement, plus drainage that accounts for the high water table. In the 94065 ZIP, a new detached ADU typically runs $90,000 to $220,000. That range includes the engineering, the piles, the dewatering, and the inspections that nearby inland cities never have to think about.
Junior ADU & Interior Conversion
For homeowners who don’t want to add square footage, a Junior ADU (JADU) converts existing interior space, often a large bedroom or bonus room, into a self-contained unit with its own entrance, kitchenette, and bath. In Redwood Shores, JADUs are popular because they usually avoid the more aggressive HOA scrutiny that attaches to detached structures. They still need permits, but the foundation is already there. If you’re in a townhome complex along one of the lagoons, this is often the fastest and most cost-effective ADU path.
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
We carry materials you can look up. On ADU and addition projects in Redwood Shores, that means Schluter systems for waterproofing wet areas, Sterling fixtures in full baths, and GAF roofing products when the addition ties into an existing roofline. We don’t stock mystery brands off the back of a van. If a spec sheet exists, we can hand it to you before you sign. And because we schedule Redwood Shores jobs in batches, we keep local stock on hand for common punch-list items, so a missing trim piece doesn’t stall your final inspection for a week.
Common Home Additions & ADU Problems We See in Redwood Shores Homes
- Underestimating dewatering needs during excavation. Contractors unfamiliar with Redwood Shores often spec standard sump pumps and get overwhelmed when water rises to 2 to 3 feet in the hole. We plan for dewatering from the first site visit.
- Ignoring HOA architectural review. Lagoon-front design guidelines and community color palettes are enforced. Skip them and you’ll be redesigning after the fact. We submit to the HOA before you buy materials.
- Voiding the builder warranty. Cutting into load-bearing walls or altering roof structure without matching the original truss layout cancels the 10-year structural warranty on many Redwood Shores homes. We check what’s still covered before we touch a wall.
- Settlement cracks after the fact. The Bay mud beneath Redwood Shores moves. An addition that isn’t tied properly to the existing pile caps will separate from the main structure within a few years. We engineer the connection so it doesn’t.
Pricing for Home Additions & ADU in Redwood Shores, CA
Here is what we tell every Redwood Shores homeowner who asks for numbers up front. A home addition in this city runs $45,000 to $130,000 depending on size, finish level, and whether it’s a ground-floor bump-out or a full second story. A garage conversion ranges $30,000 to $80,000. A new detached ADU, with the piling, drainage, and HOA approvals this soil demands, ranges $90,000 to $220,000. Yes, the groundwater and Bay mud push Redwood Shores toward the upper end of the Peninsula range. The lot conditions are real, and you should budget for them. Call (877) 610-1318 for a free estimate. We’ll walk the property, check the pile caps if accessible, and hand you a written line-item scope. No charge for the visit inside San Mateo County.
| Project Type | Typical Redwood Shores Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
We Also Serve Cities Near Redwood Shores
Our Home Additions & ADU team works throughout the mid-Peninsula. Beyond Redwood Shores, we’re on job sites in Redwood Shores, Foster City, Belmont, San Carlos, and San Mateo regularly. If you live just over the line in any of those communities, the same crew, the same written pricing, and the same 90-Day Done Right Promise apply.
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
Redwood Shores HOAs add a second approval layer that most Peninsula cities do not have. In Redwood Shores, nearly every home sits within an HOA that enforces architectural review boards, lagoon-front design guidelines, and community color palettes. Your ADU plans must pass HOA design review before the city will issue a permit. The HOA cares about rooflines, exterior materials, window styles, and even where your ADU door faces. We prepare HOA submission packages as part of every ADU design in the 94065 ZIP, which keeps your project from stalling mid-permit. Call (877) 610-1318 if you need help with the HOA layer before you even start drawings.
Usually, yes, and often at only 2 to 3 feet below grade. Redwood Shores sits on reclaimed tidal marshland, and the groundwater table is high enough that even shallow footings and utility trenches regularly hit water. On a lagoon-side lot, our crew hit groundwater at 2 feet while digging for a new footing on a 1980s tract home; we brought in dewatering pumps and an engineered pile extension before the rough-in inspection could be signed off. Any contractor bidding your addition should include dewatering in the written scope. Ours does. Call (877) 610-1318 for a free estimate that accounts for your lot’s water table.
Possibly, but only if the structural work matches the original engineering. Cutting into load-bearing walls or altering roof trusses without matching the builder’s design will void the remaining 10-year structural warranty on many Redwood Shores homes built between the 1990s and early 2000s. We check what’s still under warranty before we touch a wall. If the conversion can be done without disturbing load-bearing elements, the warranty usually survives. If not, we tell you in writing before you sign anything. Call (877) 610-1318 and we’ll check your home’s warranty status during the estimate.
Most do, yes. Nearly all of Redwood Shores sits on deep pile foundations driven through reclaimed Bay mud. Adding a second story increases the load on those piles, so the city will require an engineer to verify the existing pile caps can handle the added weight. Sometimes the existing pile system works with minor reinforcement. Other times you’ll need new piles tied into the old system. We’ve done both in the 94065 ZIP. On a lagoon-side lot, we framed a second-story addition for a 1980s tract home and had to locate the existing pile caps before setting new posts. That kind of verification isn’t optional here. Call (877) 610-1318 to get an engineer’s read on your foundation before you plan the upstairs.
Most ADUs in Redwood Shores take 10 to 16 months from first design meeting to final inspection. That breaks down roughly as: 2 to 3 months for design and HOA architectural review, 2 to 4 months for city permitting and soils engineering, and 5 to 8 months for construction depending on whether it’s a garage conversion or new detached build. The HOA layer adds time that other Peninsula cities don’t have, but skipping it costs more time than submitting properly the first time. We manage the HOA submittal, the city permit, and the construction schedule so you always know what’s next. For a specific timeline on your lot, call (877) 610-1318.
Planning an Addition or ADU in Redwood Shores Starts With Your Lot
Redwood Shores is different. The Bay mud, the pile foundations, the lagoons, the HOAs. A contractor who doesn’t know this market will underbid the dewatering, miss the HOA review, and hand you a surprise bill after the digging starts. We’ve been on these lots long enough to quote it right the first time. Every price change arrives in writing before the work happens. Every permit gets pulled and every inspection gets signed. And everything we build is backed by the written 90-Day Done Right Promise. If it’s not done right, Tom comes back and makes it right with one call.
Call (877) 610-1318 for your free estimate. A live person answers, day or night. We’ll meet you in Redwood Shores, walk the property, and give you numbers you can actually plan around.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Redwood Shores and the surrounding Peninsula.