Fast, Reliable New Detached ADU Across Hollister
Building a new detached ADU in Hollister costs $240,000 to $390,000 all-in for most lots, from geotech report through final inspection. That range includes a site-specific soils report, permit set, foundation, utility connections, and a finished 1-bedroom unit around 500 to 700 square feet. Ellery ADU Studio designs, permits, and builds detached ADUs under one contract at one written price, so the number you sign is the number you pay. Call (971) 497-2402 and we’ll put a written scope and price in front of you before any work begins.
Why Ellery ADU Studio Is Hollister’s Preferred New Detached ADU Company
Hollister sits on the Calaveras Fault, and that fact reshapes how every detached ADU here gets designed and priced. Our team has worked through the Hollister plan-check process enough times to know what the city flags, what the geotechnical reviewers ask for, and how to sequence a permit set so the fault-zone review doesn’t stall the project. We don’t treat Hollister as a satellite of a bigger market. The soil conditions, the setback rules, the summer heat load, and the city’s permitting habits are all specific to this place, and our drawings account for them from day one.
Since 2015, Ellery ADU Studio has designed, permitted, and built more than 900 ADUs, each with a written price before work started and a documented photo record when work was complete. Nadia Ellery founded the studio the year California’s ADU permitting landscape shifted, which matters because we’ve never known a version of this work that didn’t require a serious permit set. Homeowners in Hollister who call us get a written proposal with line-item pricing, not a verbal ballpark and a handshake.
Our crews serve Hollister directly. Dispatch and scheduling are coordinated from our San Francisco Bay Area office, but the people who show up on your lot know Hollister’s building department, its plan checkers, and its soil conditions. A live person answers calls 24/7. If you already have a written estimate from another builder, ask for a free second opinion. We’ll review it against what the fault-zone requirements actually demand and tell you what’s missing.
Our New Detached ADU Services in Hollister
A New Detached ADU on a Hollister lot is a different animal than one in Gilroy or Salinas because of where the fault line runs. Here is what we design and build, and how each service plays out on local ground.
Custom Built ADU
A custom detached ADU lets you size the unit to your lot’s actual buildable area after the Alquist-Priolo setback is applied. In Hollister, that setback often eats 25 feet from a mapped fault trace, which means a parcel that looked wide open on paper may only have room for a 450-square-foot studio instead of a 750-square-foot two-bedroom. We draw the unit to fit what the city will actually approve, and we do it before you’ve paid for a design you can’t build. A custom 1-bedroom detached ADU in Hollister typically runs $260,000 to $390,000 depending on foundation type and utility run length.
Studio ADU
Studio ADUs are the most common detached build we permit in Hollister because the fault-zone setback leaves less buildable ground than owners expect. A 400- to 500-square-foot studio with a full bath and kitchenette runs $230,000 to $310,000 here, including the geotech report and a mini-split system sized for inland summer heat. For a lot on the east side near the Ridgemark area or off San Benito Street where parcels run wider, a studio often fits without a variance. On older downtown lots off Monterey Street, the same studio can require creative siting to stay clear of the fault trace and existing easements.
Prefab ADU Installation
We specify and coordinate prefab systems from Abodu, Cover, Dvele, and Mighty Buildings within the same single contract. In Hollister, prefab doesn’t remove the geotech requirement or the fault-zone siting review. The unit still needs a foundation designed for local soil movement, and the site work still needs a graded pad on a parcel that may be within 25 feet of a mapped trace. What prefab does change is the construction timeline and the precision of the shell, which matters when you’re coordinating with a city that already has a long plan-check queue. A prefab studio ADU in Hollister typically runs $250,000 to $340,000 installed, depending on the brand and foundation scope.
Modular ADU
Modular detached ADUs are a strong fit for Hollister’s 1990s and 2000s tract neighborhoods, where the lots were graded decades ago and the access routes are wide enough for crane or boom delivery. We coordinate the factory-built module, the site prep, the utility stubs, and the final connection work under one contract. The catch on these newer tract lots is infrastructure: most were built without spare panel capacity or sewer laterals sized for a second dwelling. A modular 1-bedroom ADU in Hollister runs $240,000 to $320,000 before utility upgrades, and we’ll identify what those upgrades are in the written scope, not after the module is already on order.
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.
Trusted Brands We Service in Hollister
We specify and coordinate prefab and modular systems from Abodu, Cover, and Dvele more than any others on Hollister projects. Each has a different sweet spot. Abodu units suit tighter urban lots where the setback squeezes the footprint. Cover panels make sense when a homeowner wants a highly insulated shell for an inland lot that hits the mid-90s in July and August. Dvele’s offsite framing works well for 2-bedroom detached units on larger Ridgemark or Cielo Vista parcels. We keep the relationship simple: one contract, one written price, and we handle the factory coordination, the site prep, and the utility connections without handing you a vendor list to manage yourself.
Common New Detached ADU Problems We See in Hollister Homes
Every city has failure patterns. These are the four we see most often on Hollister detached ADU projects, and they’re all predictable enough to budget for before ground breaks.
- The geotech report gets skipped. Hollister plan checkers are trained to flag fault proximity on ADU submittals. We’ve seen projects stall for three to four months when a soils report wasn’t included upfront and the city requests one mid-review. The report costs $3,000 to $7,000 here depending on the parcel, and it’s cheaper than a stalled permit.
- The 1990s tract lot has no spare infrastructure. Homes in the subdivisions that pushed Hollister outward as it grew into a San Jose bedroom community were never built with ADU infrastructure in mind. Expect a new electrical subpanel, an extended sewer lateral, and fresh utility stubs on these parcels. Budget $15,000 to $40,000 for that work depending on run length and panel condition.
- The shell is underinsulated for inland heat. Hollister summer highs regularly reach the mid-to-upper 90s°F, far hotter than coastal Santa Cruz or Monterey. A detached ADU without above-code wall insulation and a dedicated mini-split becomes uninhabitable by mid-afternoon. We spec the mini-split as standard on every habitable unit here, not as an upsell.
- The owner assumes the ADU can go where the setback won’t allow it. Parcels that fall within an Alquist-Priolo Earthquake Fault Zone have a 25-foot setback from the mapped trace. That can legally prohibit a detached ADU from being sited in the backyard corner where the owner assumed it would go. The ADU goes where the fault zone allows, and the layout changes before you’ve spent money on drawings.
Pricing for New Detached ADU in Hollister, CA
A new detached ADU in Hollister runs $240,000 to $390,000 all-in, drawings through final inspection, for a finished 1-bedroom unit of 500 to 700 square feet. That range includes the geotechnical report, permit set, foundation designed for Calaveras Fault soil movement, utilities, mini-split, and finish work. A studio runs $230,000 to $310,000. A 2-bedroom detached unit runs $320,000 to $430,000 on larger parcels. What moves the number most in Hollister is the foundation type a geotech report requires, the distance from the main panel to the ADU, and whether the parcel falls within the 25-foot fault-zone setback that reshapes the layout. Every project we quote includes a written price before any work begins, per Haven Standard Clause 1, and the line-item scope stays locked at signing. Call (971) 497-2402 to schedule your free estimate.
We Also Serve Cities Near Hollister
Our crews work throughout the Hollister area and in the surrounding communities where the building rules look different. That includes Gilroy, Salinas, Watsonville, and Morgan Hill. The fault-zone siting we handle daily in Hollister is not the norm in those cities, but the ADU permitting and utility upgrade work follows the same discipline. If you’re comparing builders across city lines, we’ll show you what changes and what doesn’t.
Serving Hollister, CA - Our Local Coverage Area
We’re based in the Hollister 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 - New Detached ADU in Hollister
Yes. If your parcel falls within an Alquist-Priolo Earthquake Fault Zone, the city requires a 25-foot setback from the mapped fault trace, and that can legally prohibit a detached ADU from being sited where you assumed it would go. This is a Hollister-specific constraint that almost never comes up in Gilroy or Salinas. The first step is a geotechnical report that maps the trace relative to your property line. Call (971) 497-2402 to get a written scope that starts with the soils report before any design work happens.
Budget $15,000 to $40,000 for infrastructure upgrades on a 1950s Hollister home. That covers a new electrical subpanel (older service panels rarely have spare capacity), an extended or replaced sewer lateral, and fresh utility stubs to the ADU pad. Older homes near downtown, particularly those off Monterey Street or San Benito Street, often have original clay sewer lines that the city will require you to address once you pull an ADU permit. We write these items into the permit set and the contract before we ever put a shovel in the ground.
Because Hollister’s plan checkers are specifically trained to flag fault proximity and Alquist-Priolo compliance on every ADU submittal. In Gilroy or Salinas, a standard ADU permit set can move through plan check in a few weeks. In Hollister, the same set gets routed through geotechnical review, and if the soils report wasn’t included upfront, the project stalls for months while the city requests one mid-review. We submit the geotech report with the initial package, which is the single biggest thing you can do to keep a Hollister ADU permit moving.
It’s necessary. Hollister’s inland valley location produces summer highs regularly in the mid-to-upper 90s°F, and a detached ADU without a dedicated mini-split becomes functionally uninhabitable by mid-afternoon. The Pacheco Pass wind corridor moderates the evenings but does little to offset radiant heat gain in a poorly insulated shell. We spec a mini-split and above-code wall insulation as standard on every habitable unit in Hollister, and they’re included in the written price you sign, not added later as a change order.
Rarely. Homes in the 1990s and 2010s tract developments that expanded Hollister’s footprint were not built with ADU infrastructure in mind. Most need a new electrical subpanel, a sewer lateral extension, and fresh utility stubs to the ADU. On some lots the work is modest, $10,000 to $20,000. On others, where the panel is at the front of the house and the ADU is at the rear, the trenching alone pushes the line item higher. We identify exactly what your lot needs during the written estimate process, so there’s no surprise after the walls go up. Call (971) 497-2402 for a free estimate with line-item pricing.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Hollister and the surrounding San Benito County area since 2015.