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 Corte Madera
On a 1950s ranch on Madera Boulevard near Chapman Creek, our crew pulled off the original redwood siding and found galvanized joist hangers reduced to lace and the sill plate spongy from decades of bay-driven moisture wicking up from the crawlspace. That’s the reality of building in Corte Madera, and it’s why our approach here starts with what the salt air and creek do to a structure, not with a generic spec sheet. We’re Lodgewick ADU San Francisco, and we’ve been building accessory dwelling units, garage conversions, and home additions under The Kingswell Guarantee since 2010. Russ Delmar leads our team, and a live person answers when you call (707) 760-0502. Every Corte Madera project gets a written price before work begins, a real arrival window, a clean job site, and a written guarantee covering the full build for 365 days.
Why Lodgewick ADU San Francisco Is Corte Madera’s Preferred ADU Builders Company
Building an ADU in Corte Madera means working with a company that understands how the town’s flat, creek-side lots shape every decision from foundation to flashing. Corte Madera is the only town in Marin County where the Chapman Creek riparian corridor bisects the flat, buildable half of town. ADU setbacks here are measured from a creek’s top of bank rather than just the property line. Two identical lots on either side of Tamalpais Drive can have a 15-foot difference in where an ADU may legally sit. We walk every lot with that rule in mind before we draw anything.
Our ADU Builders team knows that a plan which works in San Rafael often fails review in Corte Madera because of creek-setback and flood-zone overlays. We handle the town’s specific requirements without drama. Homeowners here consistently tell us the two things they wanted most were a price that did not change at the door and a crew that actually showed up. The Kingswell Guarantee puts both in writing. If the work isn’t right, we come back and make it right, free, within the 365-day guarantee period. No fine print, no phone tag. When you call (707) 760-0502, a person answers.
ADU Plans in Corte Madera
ADU Plans in Corte Madera must account for the Chapman Creek riparian corridor, flood-zone boundaries, and the town’s older post-war lot patterns before a single wall is framed. We prepare plans for detached ADUs, garage conversions, JADUs (junior accessory dwelling units, typically under 500 square feet attached to or within the existing home), and studio units. A plan set for a detached ADU in Corte Madera typically runs $4,500 to $9,500 depending on whether the lot touches the creek overlay and whether structural review is required. The plan is not just a drawing. It’s the document that tells you whether your ADU is buildable at the size you want, in the spot you want, for the budget you set.
Creek Setback Mapping Before You Buy Tile
On creek-adjacent lots along Chapman Creek, we map the top of bank line first. That measurement, not the fence line, determines your legal building envelope. A homeowner who skips this step risks buying plans for an ADU that cannot be permitted where drawn. We do the mapping during the estimate phase so the written price reflects reality.
Flood Zone Documentation
Portions of flat, creek-side Corte Madera sit within FEMA flood zones. Plan sets for ADUs in those areas need elevation certificates and sometimes raised foundation details. We pull the FEMA panel for your parcel during the first site visit and build that requirement into the plan rather than discovering it at permit review.
ADU Contractor in Corte Madera
An ADU Contractor in Corte Madera carries more than a hammer and a truck. We carry the specific material knowledge this microclimate demands. Our crews have worked on the flat lots off Tamalpais Drive, the hillside parcels above Madera Boulevard, and the creek-adjacent blocks near Chapman Creek. Detached ADU construction here typically runs $310 to $425 per square foot for a site-built unit. Garage conversions usually land between $145,000 and $220,000 total depending on the condition of the existing slab and framing. Prefab and modular units from Plant Prefab or Boxabl run $190,000 to $310,000 including site work, foundation, and utility connections. Every number is written down before you sign anything.
Coastal-Spec Foundations and Flashings
Corte Madera’s proximity to San Francisco Bay means moisture moves upward through crawlspaces and sideways through siding. We spec hot-dip galvanized post bases, stainless steel connectors, and fluid-applied membranes on every exterior plane. Standard interior-grade hardware fails here within a decade. The coastal spec costs more on day one and far less by year ten.
Crawlspace Sealing and Ventilation
Flat, creek-side lots hold groundwater close to grade. We seal and condition crawlspaces with capillary breaks and dedicated dehumidification rather than relying on passive vents. The damp air near Chapman Creek will wick through an unsealed crawlspace and rot a sill plate from below while your drywall looks fine above. Russ Delmar insists on this spec for every Corte Madera build.
Trusted Brands We Service in Corte Madera
We work hands-on with several established ADU brands and material systems so Corte Madera homeowners can choose what fits their lot, timeline, and budget. For prefab and panelized builds, we install Boxabl and Plant Prefab units with the same coastal-spec foundation and flashing details we use on site-built structures. For exterior cladding that holds up against bay-driven moisture, we specify James Hardie plank with stainless fasteners rather than interior-grade nails. We also build with Tuff Shed structures for homeowners who want a permitted studio or workspace on a budget. The key is that our crews know these systems well, so the written price covers installation correctly the first time.
Common ADU Builders Problems We See in Corte Madera Homes
- Interior-grade fasteners turning to powder: Salt air plus creek humidity rusts standard galvanized nails in 5 to 7 years. Siding cups, railings loosen, and the repair bill lands right around the time the original build should have been paid off. We use stainless and hot-dip hardware exclusively on exteriors.
- Unsealed paver patios heaving at grade: Capillary rise from the high water table near Chapman Creek effloresces pavers and heaves the base within three winters. We install sealed paver systems with proper drainage and compaction so the patio stays flat.
- Pitted aluminum window frames near the bay: Uncoated aluminum within 500 feet of the bay shows pitting within two years. The thermal break fails, condensation forms on interior sills, and mold follows on drywall returns. We spec marine-grade or thermally broken coated frames for any ADU in sight of the water.
- Spongy sill plates from crawlspace moisture: Decades of bay-driven moisture wicking up from unsealed crawlspaces leaves sill plates soft and structurally compromised. We replace them, install capillary breaks, and condition the crawlspace so it doesn’t happen again.
Pricing for ADU Builders in Corte Madera, CA
A coastal-spec ADU in Corte Madera runs about 12% to 18% more than the same floor plan built in inland Marin. That’s the cost of stainless connectors, hot-dip galvanized post bases, marine-grade window frames, sealed paver joints, and conditioned crawlspaces. On a 600-square-foot detached ADU, that gap is roughly $22,000 to $38,000. The cheap spec uses interior-grade nails and standard aluminum windows, and it starts failing visibly within five winters. Plan sets run $4,500 to $9,500 depending on whether the lot touches the creek overlay. Full site-built detached ADUs run $310 to $425 per square foot. Garage conversions run $145,000 to $220,000. Prefab units from Boxabl or Plant Prefab run $190,000 to $310,000 with site work included. We give you a written price before any work starts, and that number does not change at the door. To see your exact number, call (707) 760-0502 for a free estimate.
We Also Serve Cities Near Corte Madera
Our ADU Builders in Corte Madera service covers the town itself plus nearby communities across the county line. We build ADUs in San Rafael, Sausalito, Richmond, and San Francisco. The salt-air spec shifts as you move inland, but the guarantee stays exactly the same: written price first, real arrival window, clean job site, 365-day written guarantee. Any address in these cities gets the same live-person phone line at (707) 760-0502.
Serving Corte Madera, CA - Our Local Coverage Area
We’re based in the Corte Madera 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 Corte Madera
A coastal-spec ADU in Corte Madera runs 12% to 18% more than the same floor plan inland. On a 600-square-foot detached unit, that’s roughly $22,000 to $38,000 extra for stainless connectors, hot-dip galvanized post bases, marine-grade window frames, and conditioned crawlspace work. The inland spec uses cheaper hardware that fails here in 5 to 7 years, so the coastal spec costs less over a decade. Call (707) 760-0502 for a written line-item quote on your specific plan.
Not always. Whether your ADU must be raised depends on which FEMA flood zone your parcel sits in and where the top of bank line falls relative to your buildable area. Some creek-adjacent lots require a raised foundation; others only need flood vents and an elevation certificate. We pull the FEMA panel and map the top of bank during the free estimate so you know the answer before you pay for plans. Call (707) 760-0502 and we’ll check your address.
We specify thermally broken, marine-grade coated aluminum or fiberglass frames for any ADU within 500 feet of the bay. Standard uncoated aluminum pits within two years in this salt air, the thermal break fails, and condensation on interior sills leads to mold. The marine-grade spec adds cost but eliminates that failure mode. We’ll put the exact frame material in your written quote.
We seal and condition the crawlspace rather than relying on passive vents. That means a capillary break over the grade, proper perimeter drainage, and a dehumidifier or conditioned air supply. On flat creek-side lots near Chapman Creek, the groundwater sits close enough to grade that vented crawlspaces constantly pump moisture into the structure. Sealing the crawlspace stops the wicking at the source.
The town does not mandate a specific fastener type by code, but your railing and fence will not last here with interior-grade hardware. We use stainless steel fasteners on every exterior railing, fence post base, and trim connection as standard practice in Corte Madera. It’s not a town requirement; it’s a requirement if you don’t want your railing loosening in five years. That spec is part of the 365-Day Done Right Promise, in writing, before we start.
Written by Russ Delmar, Owner at Lodgewick ADU San Francisco, serving Corte Madera under The Kingswell Guarantee.
