ADU in Redwood City, CA
Redwood City is one of the few Peninsula cities where a homeowner can walk into the Planning Division with a pre-approved ADU design and skip weeks of plan-check review. That shortcut, combined with a housing stock of 1950s ranch homes on wide lots, makes this city unusually fast ground for an accessory dwelling unit. Ellery ADU Studio handles the full ADU Design & Permitting process, Junior ADU & Interior Conversion, and ADU Site Prep & Utilities in Redwood City under one contract at one written price. Call (971) 497-2402 for a written estimate before any work begins.
Why Redwood City Homes Are Different
Redwood City’s mid-century ranch homes, concentrated in neighborhoods like Edgewood, Palm Park, and Mt. Carmel, typically run 1,200 to 1,600 square feet on 6,000 to 8,000 square foot lots. Most have detached single-car garages that are structurally sound but functionally obsolete. That footprint converts to an ADU with minimal site work. Closer to downtown, the 1920s and 1940s Craftsman bungalows tell a different story: many still have original galvanized plumbing and 100-amp panels, so a Junior ADU or interior conversion frequently starts with a 200-amp electrical upgrade and pipe replacement before framing can begin.
The climate works in a homeowner’s favor here. Redwood City gets measurably more sun and less coastal fog than San Francisco or Daly City, which makes solar-ready ADU construction particularly cost-effective. But the western hillside neighborhoods, Farm Hill and the Emerald Hills area, sit on expansive clay soils common to the Santa Cruz Mountain foothills. A detached ADU foundation on those lots routinely triggers geotechnical review that flat mid-city lots avoid entirely.
Then there is the Standard Plan Program. Redwood City was among the first Peninsula cities to launch a formal pre-approved ADU design inventory. A contractor who knows those vetted plans can tell you at the first site visit which design fits your lot and roughly how long permitting will take. That is a real advantage over out-of-area builders quoting generic plan sets written for San Jose.
Our Main Redwood City Services
Two services dominate ADU inquiries in Redwood City: converting the detached garage that came with the house, and building a new detached unit in the rear yard. Both benefit from the city’s Standard Plan Program and the large lots common to the mid-century neighborhoods.
Garage Conversion ADU in Redwood City
A garage conversion in Redwood City typically involves reinforcing the existing slab, replacing the roll-up door with a framed wall, and running new electrical and plumbing from the main house. The detached single-car garages common to Palm Park and Mt. Carmel are near-ideal candidates because the structure already exists and the setback is already legal. The city’s Standard Plan Program can shorten permitting on these jobs substantially. We write the full scope, permit set, and construction price before any work starts. For details on what a conversion involves in Redwood City, see our Garage Conversion ADU in Redwood City page.
New Detached ADU in Redwood City
A new detached ADU in Redwood City usually means a rear-yard structure of 400 to 800 square feet, sited to respect the city’s setback requirements and, on hillside lots, the geotechnical realities of expansive clay. The Standard Plan Program is most valuable here because a pre-approved design eliminates the longest variable in the schedule. We specify the foundation, the panel tie-in, and the site work as a single line item, with the permit set drawn before construction pricing is locked. For the full scope of a new build, see our New Detached ADU in Redwood City page.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
ADU Design & Permitting in Redwood City
ADU Design & Permitting in Redwood City is where the city’s Standard Plan Program changes the economics. A homeowner in a mid-century ranch in Edgewood can often use a pre-approved city design and skip the longest part of plan-check, while a Craftsman bungalow near downtown will likely need custom drawings that account for an electrical panel upgrade and galvanized pipe replacement before the permit set is complete. The permit set is the core product at Ellery ADU Studio. We draw it, submit it, and stand behind it. That is the entire point of our one-contract model: the drawings and the construction are the same contractor’s responsibility, so there is no designer-versus-builder blame gap when a revision comes back from the city. Learn more about ADU Design & Permitting and how we structure the full scope.
Site Assessment
Signs you need it
You own a lot in Farm Hill or the Emerald Hills area where expansive clay soils may trigger geotechnical review, or you have an older home whose panel and plumbing condition is unknown.
What it costs in Redwood City
Site assessment work in Redwood City typically runs $800 to $2,500 depending on whether soil testing and a survey are required for your lot.
How we do it
We measure the lot, review the city’s Standard Plan inventory against your parcel’s setbacks, and document findings with photos before any design work begins.
Permit Application
Signs you need it
You want to use a pre-approved city design to bypass weeks of plan-check, or your project requires a setback variance and you need a permit set that will pass on first submission.
What it costs in Redwood City
Permit application and plan-check fees in Redwood City typically run $3,000 to $8,000 depending on the scope and whether you are using a Standard Plan or custom drawings.
How we do it
We prepare the complete permit set, submit it to the city, respond to plan-check comments, and track the permit through approval to issuance.
Title 24 Energy Compliance
Signs you need it
Your ADU will include a new heating and cooling system, water heater, or solar-ready electrical design that must meet California energy code before the permit is approved.
What it costs in Redwood City
Title 24 energy calculations and the required documentation typically run $600 to $2,000 for an ADU in Redwood City.
How we do it
We run the energy model, specify compliant fixtures and insulation, and file the documentation with the permit set so it clears plan check without a resubmission.
What ADU Design & Permitting Costs in Redwood City
| Item | Typical range in Redwood City |
|---|---|
| Site assessment & feasibility | $800 - $2,500 |
| Permit application & plan-check | $3,000 - $8,000 |
| Title 24 energy compliance | $600 - $2,000 |
Can I use a pre-approved Standard Plan for my Redwood City ADU?
Yes, if your lot meets the city’s Standard Plan Program requirements. A pre-approved design can cut weeks from plan-check. We check your parcel’s setbacks and lot dimensions against the inventory at the first site visit, then tell you which vetted design fits. Call (971) 497-2402 for a written scope.
How long does ADU permitting take in Redwood City?
With a Standard Plan, plan-check can clear in a few weeks. Custom drawings on a hillside lot with geotechnical review take longer. We write the permit set to pass on first submission, which is the single biggest lever on schedule. Call (971) 497-2402 for a realistic timeline on your lot.
Junior ADU & Interior Conversion in Redwood City
Junior ADU and interior conversion work in Redwood City usually means converting an existing bedroom, basement, or attached space inside the home’s footprint, which avoids the site work and geotechnical issues that detached units can trigger on hillside lots. For the Craftsman bungalows near downtown, this is often the only ADU path that does not require a rear-yard addition. A Junior ADU in Redwood City can be permitted as a smaller, attached unit with its own entrance and efficiency kitchen, and the city’s permitting path for JADUs is simpler than for detached units. See Junior ADU & Interior Conversion for the full scope we handle.
Interior JADU
Signs you need it
You have an underused bedroom, den, or attached space with a separate exterior access point or one that can be added without structural change.
What it costs in Redwood City
An interior JADU in Redwood City typically runs $80,000 to $190,000 depending on the kitchen scope, bathroom addition, and whether the electrical panel can support the new load.
How we do it
We draw the JADU as a distinct unit with its own entrance, add the efficiency kitchen and bathroom within the existing footprint, and permit it under the city’s JADU provisions.
Attached Addition ADU
Signs you need it
You want a larger unit than a JADU allows but your rear yard is too small for a detached build, or your lot in Edgewood or Palm Park has setback constraints that favor an attached addition.
What it costs in Redwood City
An attached addition ADU in Redwood City typically runs $220,000 to $380,000 depending on square footage, foundation work, and whether the main home’s systems need upgrading to carry the added load.
How we do it
We design the addition to share the existing wall line, extend the foundation, tie the roof into the main structure, and run new electrical and plumbing as a single permitted scope.
What Junior ADU & Interior Conversion Costs in Redwood City
| Item | Typical range in Redwood City |
|---|---|
| Interior JADU | $80,000 - $190,000 |
| Attached addition ADU | $220,000 - $380,000 |
| Room-to-ADU conversion | $120,000 - $250,000 |
Does a Junior ADU in Redwood City need its own parking space?
No. Under California state law and Redwood City’s JADU provisions, a Junior ADU does not require additional parking. That is part of why JADUs are the fastest permitted ADU type here. Call (971) 497-2402 and we will confirm your specific lot’s requirements in writing.
Will an interior conversion trigger a full electrical panel upgrade?
Often yes, especially in the 1920s to 1940s Craftsman homes near downtown where 100-amp panels are common. We include the panel line item in the written price before work starts, per Haven Standard Clause 1. Call (971) 497-2402 for a full written scope.
ADU Site Prep & Utilities in Redwood City
ADU Site Prep & Utilities in Redwood City is where flat mid-city lots and western hillside clay soils diverge sharply on cost and schedule. A detached ADU on a ranch lot in Mt. Carmel may need only a modest foundation and a short plumbing lateral, while the same footprint in Farm Hill can require geotechnical review, deeper footings, and retaining work before utilities can be connected. Redwood City’s high sun exposure also makes solar-ready panel sizing a sensible default on new detached units, and we write that into the electrical scope from the first drawing. The full utility picture, from panel to lateral to gas, is covered under ADU Site Prep & Utilities.
Foundation & Grading
Signs you need it
Your lot is in Farm Hill or the Emerald Hills area where expansive clay soils commonly require geotechnical review, or your rear yard needs grading before a detached unit can be sited.
What it costs in Redwood City
Foundation and grading for a detached ADU in Redwood City typically runs $18,000 to $45,000 depending on soil conditions, slope, and whether retaining walls are required.
How we do it
We bring in a geotechnical engineer when the soil warrants it, design the footings to the report, and grade the site before concrete is placed.
Electrical Panel Upgrade
Signs you need it
Your home has a 100-amp panel, common in the older Craftsman bungalows near downtown Redwood City, and the ADU will add a full kitchen, laundry, and heating load.
What it costs in Redwood City
A 200-amp panel upgrade in Redwood City typically runs $3,500 to $7,500 including the new panel, meter work, and city inspection.
How we do it
We replace the panel, run the new feeder to the ADU subpanel, and coordinate the utility disconnect and reconnection with the city’s inspection schedule.
Plumbing Lateral
Signs you need it
Your existing sewer lateral is original cast iron or clay, or the ADU will sit far enough from the main line that a new lateral and cleanout are required by code.
What it costs in Redwood City
A new plumbing lateral for an ADU in Redwood City typically runs $4,000 to $12,000 depending on the trench length, depth, and whether a new connection to the city main is required.
How we do it
We locate the existing lateral, trench to the city main, install the new line with proper slope, and schedule the required city inspection before backfilling.
What ADU Site Prep & Utilities Costs in Redwood City
| Item | Typical range in Redwood City |
|---|---|
| Foundation & grading | $18,000 - $45,000 |
| Electrical panel upgrade | $3,500 - $7,500 |
| Plumbing lateral | $4,000 - $12,000 |
Do all Redwood City ADUs need a geotechnical report?
No. Flat mid-city lots generally do not, but the expansive clay soils in Farm Hill and Emerald Hills routinely trigger one for detached foundations. We only commission a report when the city or the soil conditions require it. Call (971) 497-2402 and we will check your parcel.
Will the site work price change once excavation starts?
No. Under Haven Standard Clause 5, the scope is locked at signing. If soil conditions force a change, we write the change order and you approve it before any new work begins. Call (971) 497-2402 for a written site prep estimate.
Brands We Service in Redwood City
We specify and coordinate prefab and modular ADU systems from Abodu, Cover, and Dvele within Redwood City, pairing each system’s factory tolerances with our site prep and foundation drawings. James Hardie siding is a common exterior spec on ranch-home conversions where we want the new work to read as original to the house. See our brands for the full list and how we run each system through the same single contract.
Pricing for ADU in Redwood City, CA
| Service | Typical range in Redwood City |
|---|---|
| Site assessment & feasibility | $800 - $2,500 |
| Permit application & plan-check | $3,000 - $8,000 |
| Title 24 energy compliance | $600 - $2,000 |
| Interior JADU | $80,000 - $190,000 |
| Attached addition ADU | $220,000 - $380,000 |
| Room-to-ADU conversion | $120,000 - $250,000 |
| Foundation & grading | $18,000 - $45,000 |
| Electrical panel upgrade | $3,500 - $7,500 |
| Plumbing lateral | $4,000 - $12,000 |
Prices in Redwood City push upward on hillside lots where clay soils trigger geotechnical review, and on older Craftsman homes near downtown where panel upgrades and galvanized pipe replacement are prerequisites. Every project is quoted with a written price before any work begins, per Haven Standard Clause 1, so the number you sign is the number you pay.
Neighborhoods We Serve in Redwood City
We work across Redwood City, from the flat mid-century ranch tracts to the hillside lots that need geotechnical attention before a foundation can be poured. Crews are scheduled locally and response to site visits is typically within a few business days.
- Edgewood
- Palm Park
- Mt. Carmel
- Farm Hill
- Emerald Hills
Service Area - Cities Near Redwood City
Ellery ADU Studio serves Redwood City and the surrounding Peninsula cities, including Menlo Park, CA, San Carlos, CA, Palo Alto, CA, and Belmont, CA. Each city has its own permitting office and plan-check rhythm, and we draw permit sets to the specific jurisdiction rather than recycling a generic set.
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 About ADU in Redwood City
Redwood City’s Standard Plan Program is the main difference. Homeowners can use pre-approved city designs to skip weeks of plan-check review, a shortcut that Menlo Park and Palo Alto do not offer in the same form. Pair that with large ranch-era lots and strong rental demand from the Oracle and Electronic Arts campuses, and the ADU timeline here is faster than most Peninsula cities.
Under current state law, Redwood City does not enforce an owner-occupancy requirement for new ADUs, which is part of why rental demand anchors the ROI case here. We verify the current ordinance for your specific lot and include the finding in writing with your permit set. Call (971) 497-2402 to confirm your parcel’s status.
In most cases, yes. We check your parcel’s dimensions, setbacks, and zoning against the Standard Plan inventory at the first site visit and tell you which pre-approved design fits. If none fit, we draw a custom permit set and submit it through the standard plan-check path. Call (971) 497-2402 for a free site assessment.
Call (971) 497-2402 to schedule your free estimate for any ADU project in Redwood City. Written price before any work starts, documented photo record on every visit, and the 365-Day Done Right Promise in writing.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Redwood City Customers Say
"They walked us through setbacks and utility capacity before we paid anything, and told us one of our two options was not going to get approved."
- Mireille T."Every allowance was itemised at the start, so the finish selections did not turn into a surprise at the end."
- Benedict H."Handled the whole planning process. We went to one hearing and that was it."
- Rowena C.