A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Hillsborough, CA
Hillsborough is unlike almost any other town in the Bay Area when it comes to accessory dwelling units. The half-acre minimum lot size, the design review process, and the architectural character of the housing stock mean an ADU here is rarely a simple backyard cottage. Most Hillsborough projects involve detached guest houses, garage conversions within large estate parcels, or additions that must match Spanish Colonial, Tudor, or Georgian architecture. We’re Lodgewick ADU Builders, and we approach every Hillsborough project with written pricing, a defined arrival window, and a workmanship guarantee in writing before the first nail goes in. Call (707) 760-0502 for a free estimate.
Why Hillsborough Homes Are Different
Hillsborough’s housing stock is dominated by large, custom-built homes on estate-sized lots, many built between the 1920s and 1960s. A lot of the original construction involved materials and methods that are no longer standard, which means structural work on an ADU conversion or addition often requires careful assessment of existing foundations, framing, and rooflines. The town’s design review standards are also unusually strict: any new structure visible from the street needs to harmonize with the surrounding architecture, and that shapes everything from roofline pitch to window placement and exterior finish. The mild, foggy summers and wet winters here mean moisture management and insulation matter more than extreme heating or cooling, but it also means outdoor spaces connected to an ADU can be used much of the year. Because so many Hillsborough homes sit far back from the street behind mature landscaping, utility trenching for a detached ADU often involves longer runs than a typical suburban build, which affects both cost and timeline. We plan for that reality up front.
Our Main Hillsborough Services
Most Hillsborough homeowners who call us are weighing three possibilities: building a detached ADU, converting an existing garage or guest quarters, or adding square footage to the main house. Each has its own zoning and design implications in Hillsborough, so we’ve broken them out below.
Home Addition Contractor in Hillsborough
Additions in Hillsborough often involve matching the scale and details of a large existing home, which means more than just framing new rooms. We handle complex roofline tie-ins, foundation work on sloping lots, and interior finishes that stay consistent with the original house. Because many Hillsborough properties have significant setbacks and mature trees, the site planning is often the hardest part, and that planning happens before we give you a number. See our full Home Addition Contractor in Hillsborough page for pricing and scope details.
Garage Conversion Contractor in Hillsborough
Hillsborough has a number of older detached garages and carriage-house-style outbuildings that convert well into living space, but these structures were rarely built to modern residential standards. We assess foundation condition, wall and roof insulation, electrical capacity, and drainage before quoting, because an older garage often needs substantially more than cosmetic work. The design review requirements also mean the exterior treatment of a converted garage has to respect the main house and the street view. Read more on our Garage Conversion Contractor in Hillsborough page.
ADU Builders in Hillsborough
Detached ADUs in Hillsborough are often positioned as guest houses, pool houses, or private office structures rather than rental units, and that changes the design conversation significantly. We work with prefab manufacturers and custom build teams, and we match the structure to the lot’s setbacks, utility access points, and the architectural language of the main house. Trenching, foundation work, and landscape restoration are usually part of the scope here in a way they aren’t in denser cities. Our ADU Builders in Hillsborough page covers what a typical Hillsborough build includes and what it costs.
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 Hillsborough
We work with several established prefab and materials brands, including our brands like Abodu, Plant Prefab, and James Hardie. The right choice depends on your lot, the design review constraints, and your timeline. We’ll help you match the brand to the project rather than forcing a product that doesn’t fit the property.
Pricing for ADU Company in Hillsborough, CA
| Service | Typical range in Hillsborough |
|---|---|
| Detached ADU (prefab, 400 – 600 sq ft) | $180,000 – $320,000 |
| Detached ADU (custom build, 600 – 1,000 sq ft) | $350,000 – $650,000+ |
| Garage conversion (attached, 300 – 500 sq ft) | $120,000 – $220,000 |
| Garage conversion (detached, 400 – 700 sq ft) | $180,000 – $320,000 |
| Home addition (400 – 800 sq ft, single story) | $300,000 – $500,000+ |
| Home addition (second story, 600 – 1,000 sq ft) | $450,000 – $800,000+ |
| Pool house or guest house (300 – 600 sq ft) | $200,000 – $400,000 |
| Utility trenching and site work (Hillsborough lots) | $15,000 – $50,000+ |
What pushes prices up in Hillsborough specifically is the combination of long utility runs on large lots, design review requirements that limit off-the-shelf plans, and the expectation of high-end finishes that match mansion-scale homes. Every project gets a written price before work starts, with no price changes at the door. How we quote is how we bill.
Neighborhoods We Serve in Hillsborough
We work throughout Hillsborough, including the areas most people mean when they talk about the town’s estate character and the quieter streets on the northern and eastern edges. Response times are generally measured in days for estimates, not weeks, and we schedule site walks around your availability.
- Carolands
- Lower Hillsborough
- Burlingame Hills border
- Skyfarm
- Trousdale
Service Area – Cities Near Hillsborough
Our Hillsborough work often connects to projects in nearby communities. We serve the broader Bay Area, including San Francisco, CA, Oakland, CA, Hayward, CA, and Richmond, CA. Each city has its own permitting and design context, and we handle that on a per-project basis.
Serving Hillsborough, CA - Our Local Coverage Area
We’re based in the Hillsborough 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 Hillsborough
It varies by project scope and whether the ADU is visible from the street, but Hillsborough’s design review is generally measured in months rather than weeks. We build that timeline into the schedule up front so you’re not surprised. Call (707) 760-0502 to talk through your specific project.
Yes. Utility trenching on Hillsborough’s large lots typically requires permits and coordination with service providers. We handle the permit applications and inspections as part of the project. Call (707) 760-0502 and we’ll walk you through what your lot requires.
To the extent possible, yes. We plan access routes and staging areas before work starts, and we restore disturbed landscape areas as part of the job. The Kingswell Way means we leave the property cleaner than we found it, and that’s in writing. Call (707) 760-0502 for a free estimate.
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 Hillsborough Customers Say
"The ADU came out beautiful and the permitting, which terrified me, was handled start to finish. They kept me updated every week so I was never wondering what was happening."
- Shauna Mills"Turned our detached garage into a little guest house. Clean crew, respectful of the neighbors, and no mystery charges at the end. Love how it turned out."
- Carmela Fontes"I was nervous about adding on but they walked me through every step and every cost before we started. No surprise change orders halfway through like I'd heard horror stories about."
- Eleanor Pratt
