Fast, Reliable New Detached ADU Across Redwood City
A new detached ADU in Redwood City typically costs $280,000 to $450,000 all-in, from permit set through final inspection, depending on site conditions, foundation work, and finish level. Most projects on flat mid-city lots permit in 4 to 7 months; hillside parcels in Farm Hill or Emerald Hills take longer because geotechnical review is usually required. Ellery ADU Studio has designed, permitted, and built detached ADUs across Redwood City since 2015, and we quote every project at one written price before any work begins. Call (971) 497-2402 to schedule a site visit.
We know the difference between a lot on Cordilleras Creek and one on the flats near Sequoia High School, because that difference changes your foundation line item. Our team serves Redwood City directly, with design, permitting, and construction under a single contract, so there is no designer-versus-builder blame gap when a question comes up mid-project.
Why Ellery ADU Studio Is Redwood City’s Preferred New Detached ADU Company
Redwood City homeowners keep our name in circulation for one reason: we quote a written price before work starts, and that price holds. Under Haven Standard Clause 1, every project we take on in Redwood City gets a fixed scope and a written price at signing, no door-side upsells, no change-order surprises. Our background-checked crews arrive in uniform, and our license number appears on every page and every contract.
We have built 900+ ADUs across the Bay Area since 2015, every one documented with a photo record on each visit. For Redwood City specifically, that matters because our crews know what a 1950s ranch foundation looks like after seventy years of expansive soil cycles. We do not guess. We measure, we test, and we write the scope around what we find.
Nadia Ellery, our founder, has structured the studio around the permit set as the core product. In Redwood City, where the Standard Plan Program can compress plan-check dramatically, a tight permit set is the difference between breaking ground in spring and still waiting in September.
Our New Detached ADU Services in Redwood City
Custom Built ADU
A custom detached ADU in Redwood City lets you match the massing and roofline of a 1950s ranch or a 1920s Craftsman bungalow instead of dropping a box in the backyard. We design the ADU to your lot’s actual constraints: setbacks, easements, tree protection zones, and the clay soils that show up west of El Camino Real. Custom builds on flat mid-city lots typically run $320,000 to $450,000 with a mid-range finish package.
Prefab ADU Installation
Prefab is a strong option for Redwood City homeowners who want a compressed construction schedule. We specify and coordinate systems from Abodu, Cover, and Dvele, and we handle the foundation, utility connections, and site work within the same single contract as the prefab order. One detail most homeowners miss: prefab still requires local foundation and drainage design, and Redwood City’s hillside lots rarely accept a standard prefab foundation detail without geotechnical input.
Modular ADU
Modular ADUs make sense on Redwood City lots with tight access, where a traditional stick-build would require weeks of material staging on the street. We scope crane placement, equipment access, and delivery phasing before we quote, because those logistics change the price on a lot near Edgewood or Palm Park where the driveway is narrow and the neighbors are close. Modular builds with us typically run $290,000 to $390,000, including site prep and utility connections.
Studio ADU, 1-Bed & 2-Bed ADU
A studio ADU in Redwood City runs $240,000 to $310,000; a 1-bedroom $270,000 to $360,000; a 2-bedroom $340,000 to $460,000. These are all-in ranges, drawings through final inspection, for standard site conditions. The biggest swing factors in Redwood City are foundation type (slab-on-grade versus pier-and-grade-beam on hillsides), panel upgrades, and sewer lateral condition on older homes near downtown.
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.
How Redwood City’s Standard Plan Program Changes Your Permit Timeline
Redwood City was among the first Peninsula cities to launch a formal Standard Plan Program for ADUs. That means you can use a pre-approved design on file with the city’s Planning Division and bypass weeks, sometimes months, of plan-check review. Menlo Park and Palo Alto do not offer this. For a homeowner in Edgewood or Palm Park with a straightforward lot, the Standard Plan route can compress permitting from six months to as little as a few weeks, and a contractor who knows the program can tell you at the first site visit which city-vetted design fits your lot.
Up in Emerald Hills, our crew framed a detached ADU for a homeowner whose parcel had expansive clay soil. We scoped a geotechnical review before quoting, then adjusted the foundation plan to avoid costly surprises. Because the site was on a hillside with long material hauls, we scheduled deliveries in two phases and used a compact excavator to protect the driveway. The project used a pre-approved Standard Plan to cut permit time to just a few weeks. That is the Redwood City advantage, and we build our quotes around it.
The county-versus-city split matters more in Redwood City than most homeowners realize. Parcels west of Interstate 280, especially around Emerald Hills and parts of Farm Hill, can fall under unincorporated San Mateo County control rather than city jurisdiction. That changes setbacks, fees, and septic requirements, and it changes the price. We verify jurisdiction before we quote, because a budget built on city assumptions falls apart fast on a county parcel.
Trusted Brands We Service in Redwood City
Our Redwood City projects regularly specify systems from Abodu, Cover, Dvele, and Mighty Buildings. We coordinate the prefab or modular order, the foundation, the utility connections, and the final finishes under one contract, so you are not managing three vendors. Because we stock common connection details and foundation components for these systems, our crews turn around Redwood City site work without waiting on out-of-state part shipments. James Hardie siding is our default exterior spec for detached ADUs in Redwood City, chosen for how it holds up to the Peninsula’s dry-summer climate.
Common New Detached ADU Problems We See in Redwood City Homes
- Expansive clay on western hillsides. Farm Hill and Emerald Hills sit on Santa Cruz Mountain foothill soils that swell and shrink with seasonal moisture. Skipping the geotechnical review on these lots means foundation cracks and slab movement within the first wet season after build. We scope the review before we quote.
- County jurisdiction surprises. Some Redwood City-area parcels are actually unincorporated San Mateo County. Different setbacks, different fees, and septic requirements instead of sewer. We verify jurisdiction at the first site visit and quote accordingly.
- Equipment access failures. Hillside lots with long, narrow driveways cannot always accommodate concrete trucks or cranes. That forces expensive material transfers or smaller, phased pours. We walk the access route before quoting, not after signing.
- Outdated electrical panels. 1920s to 1940s Craftsman bungalows near downtown Redwood City frequently need a 200-amp panel upgrade and galvanized pipe replacement before an ADU can be permitted. We include that line item in the written price, not as a discovery later.
Pricing for New Detached ADU in Redwood City, CA
Here are the ranges we quote in Redwood City, all-in, drawings through final inspection:
- Studio ADU: $240,000 to $310,000
- 1-Bedroom ADU: $270,000 to $360,000
- 2-Bedroom ADU: $340,000 to $460,000
- Hillside lot premium (geotechnical review, pier-and-grade-beam foundation, phased deliveries): add $45,000 to $90,000
- 200-amp panel upgrade (when required): add $4,500 to $8,000
These are written ranges, not verbal estimates. Every Redwood City project we quote gets a fixed scope and a fixed price under Haven Standard Clause 1, before any work begins. We do not use ‘call for a quote’ as a pricing strategy. We use a written price as the starting point. Call (971) 497-2402 and we will schedule a site visit, walk your lot, verify jurisdiction, and put the number in writing.
If you already have a written estimate from another builder, we offer a Free Second Opinion. Bring us the estimate, and we will go line by line: what is missing, what is overbuilt, what the Redwood City-specific risks are on your parcel.
We Also Serve Cities Near Redwood City
Our New Detached ADU in Redwood City team also works across Menlo Park, San Carlos, Palo Alto, and Belmont. Each of those cities has its own permitting quirks, but the same design-build discipline applies: written price, documented photo record, and a single contract from drawings through final inspection. If you are weighing an ADU on the Peninsula, we can tell you at the first visit what your city or county will require.
Serving Redwood City, CA - Our Local Coverage Area
We’re based in the Redwood City 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 - New Detached ADU in Redwood City
They can compress plan-check from months to a few weeks. Instead of a custom plan set going through full review, you use a city-vetted design already on file with the Planning Division. The shortcut is real, but it only helps if your lot is straightforward enough to fit one of the pre-approved plans, and if your contractor knows which plan fits your setback and lot geometry. That is the question we answer on the first site visit. Call (971) 497-2402 for a site visit and we will tell you exactly which Standard Plan fits your lot, if any.
If your parcel falls under unincorporated San Mateo County control, a detached ADU may require its own septic system or a connection to the existing system, with setback distances from the well and leach field that the city does not enforce. County parcels also have different building setbacks and fire access requirements. We verify your jurisdiction before we quote, because pricing a county parcel on city assumptions produces a budget that falls apart at permit submittal. Call (971) 497-2402 and we will pull your parcel’s jurisdiction and requirements before you commit to anything.
Yes, most 1950s to 1970s ranch lots in Edgewood, Palm Park, and Mt. Carmel are 6,000 to 8,000 sq ft, which typically leaves enough rear-yard space for a new detached ADU separate from the existing garage. The question is whether the lot’s setbacks, easements, and any protected trees allow the footprint you want. We measure the lot, check the city’s zoning code for your parcel, and tell you what fits before you spend money on drawings. Call (971) 497-2402 for a no-cost site evaluation.
They add $45,000 to $90,000 in most cases. Expansive clay soils trigger geotechnical review, which usually means a pier-and-grade-beam foundation instead of slab-on-grade. Equipment access on narrow hillside driveways forces phased concrete pours or compact equipment. Material haul distances add delivery costs. We scope all of this before quoting, so the written price reflects the hillside reality, not a flat-lot assumption. Call (971) 497-2402 and we will walk your specific site with an eye to access, drainage, and soil conditions.
It means Redwood City gets measurably more sun and less coastal fog than San Francisco or Daly City, which makes solar-ready ADU construction more cost-effective here. We frame and rough in for solar on every detached ADU we build in Redwood City, so adding panels later is a simple panel install rather than a re-roof and re-wire. The ROI on solar is stronger here than almost anywhere else on the Peninsula, and we design the roof orientation around it from day one. Call (971) 497-2402 to talk about what your specific lot’s sun exposure means for your energy math.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Redwood City since 2015.
Call (971) 497-2402 to schedule your free site evaluation and get a written price for your new detached ADU in Redwood City.
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