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 Fremont
If you’re wondering what it actually costs to build an ADU in Fremont, here’s the straight answer: a garage conversion typically runs $180,000 – $260,000, a detached one-bedroom ADU lands between $250,000 and $380,000, and a JADU conversion of existing interior space usually falls in the $90,000 – $150,000 range. Those are real numbers for Fremont’s market in 2026, not teaser figures. Lodgewick ADU San Jose coordinates dispatch from our Bay Area office, and our crews work in Fremont neighborhoods every week, from Mission San Jose to Ardenwood to Niles. If you want a written price before any work starts, call (669) 266-4319 and we’ll walk your lot with you.
Why Lodgewick ADU San Jose Is Fremont’s Preferred ADU Builders Company
Fremont homeowners call us because we put the price in writing before a single nail is driven. No change orders at the door. No “we’ll figure it out later” pricing. Our ADU Builders team has walked hundreds of Fremont lots, and the patterns are consistent: 1950s ranch homes with original panels, flat lots with drainage questions, and garages that were never meant to house a kitchen. We know what those conditions mean for the build before we quote, and we scope for them up front.
Every Fremont project runs under The Kingswell Guarantee. That means a written price, a defined arrival window, a clean job site, and a written guarantee delivered before work begins. If something isn’t right within 365 days, we come back and make it right. Russ Delmar, who leads our team, insists on that standard on every single project. A live person answers our calls 24/7, so when you call (669) 266-4319 with a question mid-build, you get a human, not a voicemail loop.
JADU in Fremont
A JADU in Fremont, also called a junior accessory dwelling unit, is a small living space of up to 500 square feet carved out of the existing footprint of your home. We convert part of a garage, a bonus room, or a underused den into an independent living area with its own entrance, a small kitchen, and often a private bathroom. Fremont homeowners choose a JADU when they need rental income or multi-generational space but don’t want the cost or footprint of a full detached build. A JADU conversion in Fremont typically runs $90,000 to $150,000, depending on whether the space needs plumbing rough-in, a new electrical subpanel, or custom cabinetry.
Garage-Conversion JADUs
In Fremont’s ranch and split-level homes, the attached garage is the most common JADU candidate. We check the existing slab, the panel capacity, and the ceiling height before quoting because those three items drive the scope. A 1960s garage with a 60-amp panel will almost always need a service upgrade before Fremont will issue a permit, and we build that into the written estimate from day one, not as a surprise add-on.
Interior-Conversion JADUs
When Fremont homeowners have a large bedroom suite or a family room adjacent to a bathroom, an interior JADU can be the most economical path. The work involves wall separation, a compact kitchenette, and a separate entrance, usually from the side yard or a covered porch. We match finishes to the existing home so the conversion reads as intentional, not tacked on.
ADU Plans in Fremont
ADU Plans in Fremont are more than blueprints. They’re the combination of site survey, floor layout, structural engineering, and the permit set the city reviews before you can break ground. Our team prepares ADU plans for Fremont properties with attention to the specific requirements that trip up first-time builders here: setback rules on flat, rectangular lots, garage-to-ADU conversion criteria under Fremont’s ADU ordinance, and the seismic detailing the city expects given the Hayward Fault proximity. Plan development for a Fremont ADU typically costs $6,000 to $14,000 depending on the complexity of the lot and whether we’re working from a prefab manufacturer’s approved design or drafting fully custom plans.
Plan Sets Matched to Your Lot
We’ve drafted plans for homes on steep Ardenwood lots, zero-lot-line Niles properties, and flat Mission San Jose ranch tracts. Each plan set accounts for drainage, access for materials delivery, and the location of existing utilities. When we hand you a plan set, it’s ready for Fremont’s plan check, not a generic template that needs three rounds of corrections.
Prefab ADU Plans and Permitting
When a Fremont homeowner chooses a prefab ADU, we work directly with the manufacturer’s design files and adapt them to the site. We handle the site plan, foundation engineering, and utility connections, and we coordinate with the manufacturer to ensure the plan set meets Fremont’s permit requirements. This saves weeks compared to drafting from scratch and keeps the written price stable because we’re not redesigning mid-stream.
Trusted Brands We Service in Fremont
We work hands-on with several established ADU brands and materials suppliers, including Abodu, Cover, and James Hardie, and we also serve Fremont homeowners who want a Tuff Shed structure finished out as a studio ADU. Our teams know the installation sequences, framing tolerances, and finish requirements for each system, so the build doesn’t stall while someone reads the manual. We keep common components and materials moving through our Bay Area supply chain, which means less waiting for Fremont projects. If you have a brand in mind, we’ll give you a straight answer on feasibility for your lot before you spend money on plans.
Common ADU Builders Problems We See in Fremont Homes
- 60-amp panels quietly killing permit applications. Fremont’s 1950s – 70s housing stock often still runs on original 60-amp electrical service. A garage conversion ADU with a kitchen and laundry will trip permitting if the panel isn’t upgraded to 200 amps, and we scope this at the first walkthrough, not after plan check rejects the submittal.
- Slab foundations that need seismic attention. Many Fremont ranch homes sit on original concrete slabs without modern hold-downs or shear detailing. Adding an ADU means the city expects seismic bracing, especially given the Hayward Fault, and we engineer the retrofit into the plan set before construction starts.
- Moisture and ventilation surprises from mild, damp winters. Fremont’s winters are wet enough to create mold problems in a wall assembly that isn’t detailed properly. We specify moisture-managed insulation and vapor control on every project, particularly for garage conversions where the original stud bays were never built for living space.
- Flat lots that look simple but aren’t. Fremont’s flat, rectangular lots seem easy for grading and drainage, but the existing pad often slopes toward the house or the garage. We re-grade and add surface drainage as needed so the new ADU doesn’t funnel water into your foundation or the neighbor’s yard.
Pricing for ADU Builders in Fremont, CA
Here’s what Fremont homeowners should expect to pay in 2026. Garage conversions: $180,000 – $260,000. Detached one-bedroom ADUs: $250,000 – $380,000. Two-bedroom detached units: $330,000 – $450,000. JADUs: $90,000 – $150,000. Prefab ADU installations with a manufacturer like Abodu or Cover: $220,000 – $340,000 including site work and utility connections. The big cost drivers in Fremont are panel upgrades, seismic retrofit on older slabs, and site preparation on lots with drainage issues. Every estimate we write is line-item and fixed. Call (669) 266-4319 and we’ll give you a real number in writing, not a ballpark that floats later.
We Also Serve Cities Near Fremont
Lodgewick ADU San Jose serves Fremont and the surrounding communities, including Union City, Milpitas, Palo Alto, and San Jose. If you’re in one of these cities and considering an ADU, the same written-price guarantee and 365-Day Done Right Promise apply. A live person answers the phone 24/7.
Serving Fremont, CA - Our Local Coverage Area
We’re based in the Fremont 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 Fremont
Fremont homes from that era were built when a 60-amp panel was enough for lights, a few outlets, and a gas furnace. Today’s ADU needs 100 amps or more just for its own kitchen, heating, and laundry circuits, so the combined load exceeds what a 60-amp service can deliver. Fremont’s building department requires the service upgrade to 200 amps before it will issue the permit. Call (669) 266-4319 and we’ll confirm your panel’s capacity during the free estimate walkthrough.
Yes. Fremont sits near the Hayward Fault, and the city’s building code requires seismic bracing and foundation anchorage when you convert an existing garage or add an ADU to a pre-1980 slab home. The specific requirements depend on the year the home was built and whether the slab has existing hold-downs. We engineer the retrofit into your plan set so the cost is known before construction starts.
Fremont’s mild, damp winters mean wall assemblies need proper vapor control and insulation strategies that prevent condensation from collecting inside the framing. We specify moisture-managed insulation, correctly detailed WRB (weather-resistant barrier), and ventilation that keeps the interior dry year-round. Detached ADUs on open lots also need their own drainage detailing so winter rains don’t collect at the foundation. Call (669) 266-4319 for an exact scope.
No. A 60-amp panel cannot safely serve an ADU with a kitchen, heating, and laundry, and Fremont’s permitting will reject a plan that doesn’t include the 200-amp service upgrade. The upgrade typically costs $4,000 – $6,000 in Fremont, including the new panel, grounding, and coordination with PG&E if the service drop needs replacement. We include this in the written price before work begins, never as an add-on later.
Flat lots seem forgiving, but in Fremont the existing slab often drains toward the home or garage. Adding an ADU changes the impervious surface area, which can push water toward foundations unless we re-grade the pad and add surface drainage. We evaluate slope, soil type, and the existing drainage pattern during the estimate. Call (669) 266-4319 to schedule your free walkthrough.
Written by Russ Delmar, Owner at Lodgewick ADU San Jose, serving Fremont and the surrounding Bay Area since 2010.
