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 Martinez
Most ADU projects in Martinez start with a garage that’s been standing since the 1940s or a backyard that’s bigger than the house needs. The question isn’t whether you can build an accessory dwelling unit here. It’s what the existing structure will require once we open it up. That’s the part nobody tells you about until it’s too late. Our crews work Martinez neighborhoods weekly, from the flats near the Amtrak station to the hillside lots off Alhambra Avenue, and we’ve learned exactly what these older properties throw at you. Call (707) 760-0502 and we’ll talk through your specific lot before you spend a dime.
Why Lodgewick ADU San Francisco Is Martinez’s Preferred ADU Builders Company
Russ Delmar leads our Martinez ADU work, and he’s walked enough pre-1960s garages in this town to know what’s behind those stucco walls before the first hammer swings. Homeowners here keep telling us the same thing: they got a quote from someone who never looked under the slab, and the price changed a week into demo. We don’t work that way. The Kingswell Guarantee puts a written price in your hands before we start, along with a defined arrival window and a written warranty on the finished build. If something isn’t right within 365 days, we come back and make it right. That’s not a slogan. It’s on paper.
We’re the ADU Builders team that Martinez homeowners call when they want the inspection done before the quote, not after. Our office coordinates scheduling from the San Francisco Bay Area, but the crews working your property live in Contra Costa County and know Martinez’s building department, its permitting quirks, and its soil. That local familiarity changes how we bid, how we schedule, and what we catch early.
ADU Design in Martinez
ADU Design in Martinez starts with the lot and the existing structure, not with a catalog floor plan. A 700-square-foot backyard off Morello Avenue has different setback requirements than a detached garage conversion on a hillside parcel near Mountain View Drive, and the design has to account for Martinez’s summer heat and winter rain. We handle the full design package: site survey, floor plans, structural engineering for any existing garage work, Title 24 energy calculations, and the permit set the city will actually approve. A complete ADU design in Martinez typically runs $8,000 to $18,000, depending on whether it’s a simple garage conversion or a new detached build with a hillside foundation. Russ Delmar reviews every design before it goes to the city, because he’s the one who has to build it.
What Older Garages Force Us to Design Around
Downtown Martinez has dozens of detached garages built between 1920 and 1959. Most sit on slab-on-grade concrete with no perimeter drainage and footings that wouldn’t pass today’s shear requirements. The design phase is where we catch this. We specify the structural retrofit before finish materials, so the plan the city approves matches the house we actually build.
Written Design Scope, No Open-Ended Hours
Design hours can balloon when revisions pile up. We write our design scope into the contract the same way we write construction scope: fixed price, named deliverables, and a written change order if you add something mid-design. You’ll know what the plans cost before we draw line one.
Backyard ADU in Martinez
Backyard ADU in Martinez construction usually means one of two things: converting a detached garage that’s already there, or building a new standalone unit in the yard. Both are popular here because Martinez lots tend to be generous compared to newer Contra Costa suburbs, and the city’s ordinances allow accessory units on most single-family parcels. A new detached backyard ADU in Martinez, finished to code, typically runs $280,000 to $420,000 for a 600 to 800 square foot unit, including foundation, utility connections, and finishes. Garage conversions usually land between $160,000 and $260,000, before any structural surprises we find during inspection.
Hillside Lots Change the Foundation Math
Properties up toward the hills above downtown, along streets like Berrellesa or up near Rankin Park, often need a stepped or pier-and-grade-beam foundation instead of a simple slab. That adds $20,000 to $45,000 to the foundation line item depending on slope and soil. We’ll tell you which foundation your lot actually needs before we bid, not after we dig.
Prefab Options for Faster Backyard Builds
Some Martinez homeowners want a faster path, and we install prefab units from manufacturers like Plant Prefab and Abodu. These units get built in a factory while we handle site prep, foundation, and utility connections on your property. A prefab backyard ADU in Martinez typically runs $220,000 to $380,000 delivered and connected, and the site work still matters as much as the unit itself. The Kingswell Guarantee covers the entire project, prefab or stick-built.
Trusted Brands We Service in Martinez
When a Martinez ADU calls for prefab or manufactured components, we work with the brands homeowners here ask about most. We’ve installed Abodu units on flat downtown lots, specified James Hardie siding and trim on custom builds where fire resistance matters on the hillsides, and used Plant Prefab panels for projects with tight lot access off narrow streets like Ward Street. Because our crews handle these systems regularly, we can order components quickly and coordinate factory delivery with site readiness. A live person answers our phone 24/7, so when your prefab arrives early or a panel shows up damaged, you reach a human who can act, not a voicemail.
Common ADU Builders Problems We See in Martinez Homes
- Undersized footings under pre-1960s garages. Most downtown Martinez garages from this era have footings that would fail today’s shear and uplift requirements. Converting one without a structural upgrade means the building department won’t sign off, and retrofitting after demo costs more than planning for it.
- Electrical panels that can’t handle a second dwelling. Many older Martinez homes still run 100-amp panels, but an ADU with its own kitchen needs a separate feed. The permit for your ADU will trigger a panel upgrade on the main house in most cases, and that’s a $4,000 to $8,000 line item you want in the original contract, not a surprise.
- Winter drainage on hillside lots. Martinez gets most of its rain between November and March, and hillside yards move water fast. Without proper perimeter drainage and a waterproofing membrane at the foundation, a backyard ADU can start taking on water the first winter after it’s built. We design drainage before we pour.
- Old slab-on-grade with no vapor barrier. Garages built before the 1960s in Martinez often have slabs poured directly on soil with no capillary break. That means moisture wicks up through the concrete, and any finished floor we install over it will fail. We address this at inspection, not after flooring goes down.
Pricing for ADU Builders in Martinez, CA
Here are the ranges we quote most often in Martinez as of this year. A garage conversion into a studio ADU runs $160,000 to $260,000. A one-bedroom backyard ADU built new runs $280,000 to $380,000. A two-bedroom detached unit runs $350,000 to $420,000. Hillside foundation work adds $20,000 to $45,000. Electrical panel upgrades run $4,000 to $8,000. Full ADU design and permit sets run $8,000 to $18,000. These aren’t teaser numbers. They’re what we’ve actually written into Martinez contracts. What moves the final number is what we find during inspection: footing condition, panel capacity, drainage, and slope. We build a written allowance into the contract for the structural unknowns we can’t see until walls are open, and anything we spend against that allowance gets priced and approved in writing before we touch it. Call (707) 760-0502 for a free estimate on your specific lot.
We Also Serve Cities Near Martinez
Our crews work throughout central Contra Costa County. Many of our Martinez clients have family or rental properties in nearby communities, so we regularly take on ADU projects in Orinda, Moraga, Richmond, and Emeryville. If you’re just starting to research ADU options, our ADU Builders in Martinez page covers what local permits and lot conditions mean for your timeline and budget.
Serving Martinez, CA - Our Local Coverage Area
We’re based in the Martinez 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 Martinez
Pre-1960s garage footings in Martinez are almost always undersized for current California shear and uplift requirements, which means the structural retrofit adds $15,000 to $35,000 to a garage conversion. We inspect the footing depth and condition before we quote, so this number is in your written price from the start. Call (707) 760-0502 to schedule a footing inspection on your garage.
Opening walls in a pre-1970s Martinez home typically triggers an electrical panel upgrade to 200 amps, smoke and carbon monoxide detector additions throughout the existing structure, and sometimes water heater strapping or seismic upgrades. We budget a written $4,000 to $8,000 allowance for these code-triggered items so they don’t surprise you mid-project. Get an exact scope from Russ Delmar before you commit.
We don’t treat failed waterproofing as a surprise. Our inspection includes checking foundation walls and slab edges for moisture intrusion before we quote, and our contract carries a written waterproofing allowance for what we can’t see until the walls are open. If we find failed waterproofing during demo, you approve the written change order and the cost before we do the work. That’s the Kingswell Way.
We write a structural allowance into older Martinez ADU conversions because nobody can see what’s behind a 1940s stucco wall or under a 1950s slab until it’s open. A fixed bid on an old garage either pads the price to cover worst-case unknowns, or it’s a lowball that becomes a five-figure change order after demo. Our allowance is transparent: a named dollar amount for specific structural work, spent only with your written approval, and any portion we don’t use comes off your final invoice. Call (707) 760-0502 for a free estimate that explains exactly how the allowance on your project would work.
Many hillside lots in Martinez do require a new engineered foundation system, typically a stepped footing or pier-and-grade-beam design, which runs $20,000 to $45,000 depending on slope and soil conditions. Flat lots can often use a standard slab-on-grade foundation. We’ll tell you which your lot needs during the free estimate, before you’re committed to anything.
Ready to talk numbers for your Martinez lot? Call (707) 760-0502 and a live person will answer, day or night. We’ll schedule a free on-site inspection, walk the property with you, and put a written price in your hands before any work begins. Russ Delmar and the Lodgewick team have been doing this since 2010, and the guarantee is on paper every time.
Written by Russ Delmar, Owner at Lodgewick ADU San Francisco, serving Martinez and the surrounding Contra Costa County area.
