A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable ADU Builders Across Kentfield
Adding an ADU in Kentfield means working with a builder who understands hillside geotechnical requirements, Ross Valley flood zone rules, and the county’s protected oak tree ordinance before a single plan is drawn. Most detached ADUs in Kentfield run $230,000 to $380,000 depending on site conditions, and the geotech report alone can reshape your budget months before demo starts. Sutton ADU San Francisco has been building and converting accessory dwellings since 2006, and we send every Kentfield homeowner a written price before work begins, along with the name and photo of the crew lead who will show up at your door. Call (831) 272-7212 to talk through your lot, your setbacks, and your options.
Why Sutton ADU San Francisco Is Kentfield’s Preferred ADU Builders Company
Kentfield is not a flat-lot town. Our ADU Builders team has walked the Crown Road hillsides, the estate lots off Woodland Road, and the older neighborhoods near Sir Francis Drake Boulevard where 1950s and 1960s homes sit on generous parcels. That matters because a builder who only works flat inland lots will quote you a number that does not survive first contact with a slope, a flood map, or a heritage oak.
Every Sutton project in Kentfield operates under the Threshold Standard. That means a background-checked, identity-verified, photo-badged technician is the person you see at the door, and that person’s name and photo arrive in your inbox before the visit. Miles Hartwell, who leads our team, insists on written change orders for anything uncovered once walls are open. No silent scope creep. No invoice shock.
We work with prefab and modular systems including Plant Prefab and Abodu, and we stock scheduling priority for Kentfield customers so permit-ready plans do not sit idle. Homeowners who care about who is on their property, and about a 365-day written guarantee on workmanship, tend to find us by referral here.
ADU Plans in Kentfield
ADU Plans in Kentfield are not a formality. They are the document set that proves to the County of Marin that your structure will survive the slope, drain the stormwater, and respect the oaks. Nearly every Kentfield ADU on a hillside lot triggers a geotechnical report requirement, and properties near Corte Madera Creek often need a stormwater mitigation plan showing how runoff will be detained or filtered before it leaves your parcel. You do not want to discover these requirements after you have filed with the county.
Geotechnical and Drainage Design
On sloped lots, the soils report dictates foundation type, depth, and sometimes the entire placement of the structure. If the geotech engineer finds expansive clay or undocumented fill, your foundation cost can shift by tens of thousands. We bring the engineer in during planning, not after the county sends a correction notice.
Oak Tree and Setback Compliance
Kentfield enforces strict tree ordinances that can dictate where your foundation sits and how high your roof rises. A protected oak near your proposed build site means the plan has to work around the drip line, not through it. We survey for these constraints in the first week, before you spend money on plans that will not pass.
ADU Contractor in Kentfield
An ADU Contractor in Kentfield has to be more than a framing crew. The job starts with opening walls on a 50 or 60-year-old structure and finding what is actually behind the sheetrock: undersized rafters, knob-and-tube wiring, failed sill plates, dry rot at the mudsill. How the contractor handles those discoveries determines whether your project stays on budget or quietly doubles.
Inspection-First, Allowances Written In
We inspect before we bid. When we open a wall or a ceiling, we already know what we are likely to find, and we write realistic allowances for the ugly stuff into your contract. If something genuinely unforeseen appears, you get a written change order with a fixed price, and you approve it before we touch the work. The 365-Day Done Right Promise covers what we build for a full calendar year.
Prefab and Modular Coordination
For homeowners who want a faster build, we act as the local GC for Plant Prefab and Abodu installations. That means we handle the site work, foundation, utilities, and finish, while the factory handles the module. You get a single point of contact and a written price, not two companies pointing fingers.
Trusted Brands We Service in Kentfield
We work regularly with Plant Prefab and Abodu panels and modules, and we are fluent in James Hardie exterior systems for Kentfield homes that need fire-resistant cladding in the wildland-urban interface. Because we schedule local crews for Kentfield projects, we can move quickly when plan sets are approved and materials are released. If you are deciding between a prefab system and a custom stick-built ADU, we will give you honest guidance on which fits your lot shape, your access, and your budget. No brand loyalty. Just what works on your street.
Common ADU Builders Problems We See in Kentfield Homes
- Flat-lot pricing that collapses on a hill. A builder quotes you a number based on a level pad, then discovers your site needs $40,000 in pier drilling or a retaining wall once grading begins. We price from the geotech report, not before it.
- Protected oaks discovered too late. The county’s tree ordinance forces a foundation redesign after plans are filed and permits are in review. We identify tree constraints in week one.
- Stormwater mandates near Corte Madera Creek. Properties in the Ross Valley flood zone often need bioswales or detention tanks to satisfy county drainage rules. A last-minute detention system can add five figures. We plan for it.
- Surprise knob-and-tube wiring in older garages. Opening a 1960s Kentfield garage for a conversion regularly reveals wiring that cannot be extended legally. Our inspection catches it before demo, and we price the panel upgrade and rewiring as a written allowance.
Pricing for ADU Builders in Kentfield, CA
A detached ADU in Kentfield typically runs $230,000 to $380,000 for a 600 to 1,000 square foot unit, before site-specific geotechnical and drainage work. Garage conversions land between $140,000 and $220,000 depending on framing repairs and electrical upgrades. A junior ADU inside an existing home runs $90,000 to $160,000. Hillside retaining walls, pier drilling, and stormwater detention tanks add $30,000 to $70,000 when they are required. A soils report in Kentfield typically costs $4,000 to $9,000. Every Sutton project includes a written line-item price before work starts, and the 365-Day Done Right Promise in writing. Call (831) 272-7212 for a free estimate at your Kentfield property.
We Also Serve Cities Near Kentfield
Sutton ADU San Francisco serves Kentfield and the surrounding Marin communities, including San Anselmo, Fairfax, Novato, and San Pablo. If you are just over the town line, the same Threshold Verified crews and written-pricing standard apply.
Serving Kentfield, CA - Our Local Coverage Area
We’re based in the Kentfield 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 Builders in Kentfield
Yes. Kentfield’s hillside zoning makes a geotechnical report a standard permit requirement for any ADU on a lot with more than a modest slope. The report determines foundation type, depth, and drainage requirements, and it must be completed before structural plans are finalized. We bring in a licensed geotechnical engineer early so the report is part of the plan set, not a correction. Call (831) 272-7212 and we will walk you through what your specific lot will likely need.
We inspect before we bid, and we write realistic allowances into your contract for the discoveries that are common in 1950s-1970s Kentfield garages: undersized rafters, knob-and-tube wiring, failed sill plates, and dry rot. If we open a wall and find something outside the allowance, you get a fixed-price change order in writing and you approve it before we proceed. No silent charges. Call (831) 272-7212 to schedule a free inspection.
Yes, in many Kentfield homes built before 1980, an ADU addition pushes you past the capacity of the existing panel, and the county will require an upgrade to at least a 100-amp or 200-amp panel depending on your loads. We inspect the panel during our initial site visit and include the upgrade in your written price if it is needed. Call (831) 272-7212 for a free on-site assessment in Kentfield.
Kentfield protects significant oaks and other mature trees, and the ordinance can restrict foundation placement, roof height, and even construction access within the tree’s dripline. If a protected tree sits near your proposed build site, the plan has to work around it, not remove it. We flag tree constraints during our first site walk so your plans reflect them from day one. Call (831) 272-7212 to schedule a property review.
Properties near Corte Madera Creek fall within the Ross Valley flood zone and typically must include a stormwater mitigation plan showing how runoff from the new impervious surface will be detained or treated before leaving the parcel. That often means a bioswale, a detention tank, or both, and those systems can add $20,000 to $50,000 to the project. We include stormwater design in our planning scope so you see the full cost before you commit. Call (831) 272-7212 for a free estimate.
Contact Sutton ADU San Francisco in Kentfield
If you are planning a detached ADU, a garage conversion, or a room addition in Kentfield, start with a conversation about your specific lot, your trees, and your slope. We will send a background-checked, photo-badged technician to walk your property, and you will receive a written price before any work begins. The 365-Day Done Right Promise covers your completed build for a full year. Call (831) 272-7212 to schedule your free estimate.
Written by Miles Hartwell, Owner at Sutton ADU San Francisco, serving Kentfield since 2006.
