A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Half Moon Bay, CA
Half Moon Bay is a coastal town where ADU projects rarely follow a standard playbook. The housing stock runs from 1970s and 1980s single-family homes on septic-ready acreage to small, nonconforming beach cottages near the water. Combine that with fog, salt air, and Coastal Act oversight, and you get jobs where the right material and the right permit strategy matter more than anywhere else along the Peninsula. We approach every Half Moon Bay ADU project as a site-specific build, not a copy of the last job. Call (424) 328-5746 to talk through your property’s options.
Why Half Moon Bay Homes Are Different
Coastal fog doesn’t just dampen the morning drive. It keeps siding, flashing, and framing damp for months at a stretch. In Half Moon Bay, an ADU built with inland-California habits fails early and expensively. We specify James Hardie cladding and full envelope ventilation on coastal jobs because we’re building against persistent moisture and salt spray, not just rain. Older garages near the water bring a second issue: many were converted from pump houses or boat storage decades ago, and their slabs show salt-corroded spalling concrete. Before we price a conversion in the western neighborhoods, we check the foundation. A garage ADU that looks like a simple finish job can become a structural correction once the concrete tells its story.
Permitting adds another layer. The Coastal Act’s rules on nonconforming structures and view-shed protection mean a design that flies in San Mateo may get sent back for revision in Half Moon Bay. Attached conversions and modular units placed within an existing footprint often clear review faster than a new two-story detached unit. We plan for that from the first conversation, and we put the written price on the table before anything goes to the city.
Our Main Half Moon Bay Services
Most Half Moon Bay homeowners call us about one of three projects: a new ADU, a home addition, or a room addition. Each service has its own detailed Half Moon Bay page below, so you can go straight to the pricing and local specifics for what you’re planning.
ADU Builders in Half Moon Bay
A coastal-side ADU in Half Moon Bay usually means either a detached prefab unit placed within an existing footprint or an attached conversion from a garage or unused wing. The Coastal Commission caps size and height on many parcels, so design choices that preserve view-sheds matter. We build with prefab brands like Abodu and Plant Prefab, which gives you a faster frame and a cleaner permit package than full site-built construction. Read the full Half Moon Bay ADU breakdown here: ADU Builders in Half Moon Bay.
Home Addition Contractor in Half Moon Bay
Home additions in Half Moon Bay tend to grow the footprint of 1970s and 1980s ranches, often on large lots with septic systems that constrain where new square footage can go. If the house sits close to a bluff or a protected view corridor, the addition may need to step down in height. We handle the septic clearance, the set-back math, and the coastal review paperwork as part of the build. Half Moon Bay specifics and pricing: Home Addition Contractor in Half Moon Bay.
Room Addition Contractor in Half Moon Bay
A room addition here is rarely just one room. The work usually involves converting a damp, uninsulated space into a finished bedroom, office, or family room that can hold temperature in a foggy marine climate. We budget for envelope upgrades, vapor barriers, and moisture-rated insulation rather than treating it as a drywall-and-paint job. That’s the difference between a room that lasts and one that smells musty by March. The full scope and Half Moon Bay price ranges: Room Addition Contractor in Half Moon Bay.
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.
Brands We Service in Half Moon Bay
We build with brands homeowners can research themselves: Abodu, Plant Prefab, Tuff Shed, and James Hardie materials. Coastal-rated cladding and prefab panels are stocked through our Bay Area supply chain, which keeps lead times on Half Moon Bay projects shorter than fully custom orders. See our brands for what each one offers.
Pricing for ADU Company in Half Moon Bay, CA
| Service | Typical range in Half Moon Bay |
|---|---|
| Detached ADU (prefab, 400 – 600 sq ft) | $180,000 – $320,000 |
| Attached ADU (garage or wing conversion) | $140,000 – $260,000 |
| ADU site prep and foundation correction | $18,000 – $45,000 |
| ADU coastal permit and design package | $12,000 – $30,000 |
| Home addition (ground-level, 300 – 500 sq ft) | $150,000 – $320,000 |
| Home addition (second-story, 300 – 500 sq ft) | $220,000 – $420,000 |
| Room addition (single room, 150 – 250 sq ft) | $80,000 – $160,000 |
| Garage conversion to finished room | $70,000 – $150,000 |
| Full envelope upgrade (insulation, vapor barrier, cladding) | $25,000 – $60,000 |
| Foundation or slab repair before ADU build | $8,000 – $35,000 |
Coastal review, spalling-concrete remediation, and septic limitations are the three biggest price movers in Half Moon Bay. Every project starts with a written price before any work begins, so you’ll know the full figure, not a range that balloons later.
Neighborhoods We Serve in Half Moon Bay
We cover the full Half Moon Bay area, from the bluff-front homes near the ocean to the larger lots east of Highway 1 and the hillside streets rising toward the preserve. Coastal and inland parcels get the same written-price treatment before we touch a tool.
- Miramar
- El Granada side of the city line
- Frenchmans Creek
- Downtown Half Moon Bay
- Highlands
Most Half Moon Bay estimates are scheduled within a few days of your call, depending on site access and the size of the project.
Service Area – Cities Near Half Moon Bay
Our team also covers the neighboring communities along the coast and up the Peninsula. If your property sits close to a city line, we’ll tell you which jurisdiction applies before the permit goes in. Nearby areas include El Granada, CA, Burlingame, CA, San Francisco, CA, and Castro Valley, CA.
Serving Half Moon Bay, CA - Our Local Coverage Area
We’re based in the Half Moon Bay 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 Company in Half Moon Bay
Yes. We prepare the design and permit package with Half Moon Bay’s coastal overlay in mind, including height, set-back, and view-shed compliance. Call (424) 328-5746 and we’ll walk through your parcel’s review path on the first call.
Fog drives up the moisture load on every surface. We specify coastal cladding, vapor barriers, and continuous ventilation from the start, which prevents the mold and rust problems that show up two or three years after a cheaper build. The envelope upgrade is priced upfront.
Usually yes, with the right placement. Septic setbacks often limit where a detached ADU can sit, but attached conversions and units within an existing footprint avoid most conflicts. We’ll check your septic plan before quoting.
Call (424) 328-5746 for a free estimate on your Half Moon Bay ADU, home addition, or room addition. You’ll get a written price and a straight answer on what your property can support.
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 Half Moon Bay Customers Say
"Booked a consult online and met the project manager two days later. Weekly progress updates arrived by text with photos. ADU finished on schedule."
- Hannah W."Great build. Inspection delay, the county's fault, pushed things a week, but updates were clear."
- Soo-jin P."Garage conversion into a guest suite. I could see the permit status in the app, which made it painless."
- Rick F.
