Fast, Reliable ADU Builders Across San Bernardino
If you’re searching for ADU builders who actually understand San Bernardino’s lots, permit office, and older housing stock, you’ve found us. We’re Cottage ADU Builders, and we’ve worked on detached units, garage conversions, and custom backyard homes across 92404, 92405, 92410, and 92411. San Bernardino isn’t Redlands or Rancho Cucamonga. The lots are wider, the garages are detached, and the homes were mostly built between the 1940s and 1970s. That changes how an ADU gets designed, permitted, and built. Call (866) 808-7312 and we’ll tell you exactly what’s possible on your lot.
Why Cottage ADU Builders Is San Bernardino’s Preferred ADU Builders Company
The short version: we speak prefab and modular fluently, and we’ve done enough ADUs in San Bernardino to know which permit reviewer wants which detail. But the longer answer matters more. Most general contractors treat an ADU as a side project between kitchen remodels and roof repairs. We don’t. ADUs, kitchens, and bathrooms are our entire scope. That focus shows up in the way we sequence site prep, utility connections, and long-lead material orders.
Our owner, Neil Stratton, built this company around one conviction: a second unit shouldn’t mean a second contractor. When you work with us on a detached ADU in San Bernardino, the same crew handling the structure can also finish the kitchen and bath inside it. That’s not a convenience pitch. It’s a coordination reality. Fewer handoffs mean fewer schedule gaps and fewer change orders. For San Bernardino homeowners planning multigenerational housing or a rental unit, that coordination is the difference between a twelve-month project and a sixteen-month one.
We’re also licensed and insured, and every estimate is free. You’ll get a written line-item quote before any work starts, and we stand behind our workmanship. If you want to talk to past San Bernardino clients, ask us. We’ll connect you.
ADU Plans in San Bernardino
ADU Plans in San Bernardino start with understanding what the City will approve on your specific lot, and what your existing electrical and plumbing can support before you fall in love with a design. We pull permits, we handle the City’s ADU review process, and we coordinate with your designer or architect when the project calls for it. A full plan set typically runs $4,000 to $9,000 depending on complexity, but that figure includes structural engineering, Title 24 energy calculations, and permit-ready drawings, not just a pretty render.
Site Feasibility Surveys
Before we draw anything, we walk the lot. In 92404 and 92405 especially, wide side yards and alley-facing detached garages create opportunities you won’t find in denser cities. We measure setbacks, check the service panel, and assess whether your sewer line and water meter can handle a second dwelling. That survey costs nothing during the estimate phase, and it prevents the most expensive mistake in ADU planning: designing a unit your lot can’t support.
Structural and Energy Drawings
San Bernardino summers routinely pass 100°F, and Title 24 energy compliance isn’t optional. Our plan sets include window specs, insulation values, and HVAC sizing calculated for this valley’s heat, not a generic California template. If you’re working with an architect, we coordinate directly with them. If you’re not, we can recommend local designers familiar with the City’s ADU checklist.
ADU Contractor in San Bernardino
Hiring an ADU Contractor in San Bernardino means choosing someone who manages the whole job from permit to punch-list: demo, foundation, framing, siding, rough-in, finishes, and final inspection. A standard detached ADU here typically runs $250 to $420 per square foot, with prefab and modular units sometimes landing lower depending on site prep. Garage conversions in 92410 and 92411 usually come in around $150 to $260 per square foot, since the shell already exists.
Detached and Garage Conversion Builds
On San Bernardino’s post-war bungalows, detached garages fronting alleys are everywhere. Converting one into a studio or one-bedroom ADU is often the fastest path to rental income, and we’ve done dozens. What many homeowners don’t expect is the electrical upgrade: older single-panel service won’t carry an ADU’s HVAC load, and that replacement gets factored into the fixed price before we start.
Prefab and Modular Installations
We work with the brands you’ve already been researching: Boxabl, Plant Prefab, Tuff Shed, Abodu, Cover, Dvele, and Mighty Buildings. Your lot, your budget, the right system. We know factory timelines, crane scheduling, and how San Bernardino’s permit office handles factory-built housing submittals. That knowledge gap trips up contractors who only know stick-frame.
Trusted Brands We Service in San Bernardino
As ADU Builders who install prefab systems, we work with Boxabl and Plant Prefab for modular units, Tuff Shed for rapid studio conversions, and James Hardie fiber-cement siding on exteriors that need to stand up to Inland Empire heat and Santa Ana winds. We don’t push one brand. We match the system to your lot, budget, and timeline. If you’ve already researched Abodu or Cover, we’ll speak that language fluently and tell you honestly whether it fits your San Bernardino site. Built to last on the outside, livable on the inside.
Common ADU Builders Problems We See in San Bernardino Homes
- Older electrical service can’t carry the load. Homes built in the 1950s and 1960s across 92404 and 92405 often still have 60-amp or 100-amp panels. Adding an ADU’s HVAC, range, and lighting usually triggers a panel upgrade, and we identify that in the feasibility survey so it’s in the fixed price from day one.
- Spec-grade windows fail fast in valley heat. San Bernardino hits 100°F or higher most Julys and Augusts. Cheap dual-pane windows with aluminum frames warp and leak. We spec thermally broken frames and low-E glass rated for this climate, not for coastal fog.
- Designer finishes ordered before the site is verified. You pick Italian tile and a custom steel door, then the plumber discovers cast-iron drain lines that need replacement. We sequence the design selection after the site survey, so your millwork order is never at risk from a hidden plumbing surprise.
- Long-lead items blow up the calendar. Custom cabinetry takes ten to fourteen weeks. Imported tile can take six months. Lead times, not labor, set the schedule on high-end ADUs. We order long-lead items the moment your permit is approved, and we lock pricing in writing before the order is released.
Pricing for ADU Builders in San Bernardino, CA
San Bernardino’s ADU market leans multigenerational and rental-focused, which means budgets here run lower than the upscale backyard office builds you’ll see in Redlands or Rancho Cucamonga. But high-end work still happens, and when it does, the honest pricing reality applies: a detached one-bedroom ADU with custom millwork, architectural glass, and designer finishes lands between $320 and $450 per square foot all-in. A garage conversion in 92404 with a full kitchen and bath typically runs $180,000 to $280,000 total. Prefab options from Boxabl or Plant Prefab can start lower, around $120,000 to $200,000 for a turnkey studio, depending on site prep and utility runs. The single most important protection is a written fixed price before long-lead orders go out. We do that on every job. Call (866) 808-7312 for a free estimate and a line-item quote with no change-order surprises.
We Also Serve Cities Near San Bernardino
Our crews cover ADU Builders in San Bernardino plus the surrounding Inland Empire communities: Muscoy, Highland, Loma Linda, and Rialto. If you’re in one of those cities and weighing an ADU, a kitchen remodel, or a bath renovation alongside it, the same estimate process applies. Call and we’ll schedule a site walk.
Serving San Bernardino, CA — Our Local Coverage Area
We’re based in the San Bernardino 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 San Bernardino
They set it. Custom cabinetry runs ten to fourteen weeks from order to delivery. Imported tile can take five to six months. Custom steel doors and architectural glass often run eight to twelve weeks. On a high-end ADU in San Bernardino, we order these items the day your permit clears, and we build the construction schedule backward from those delivery dates. Labor is rarely the bottleneck. Material lead times are. Call (866) 808-7312 for an exact schedule on your project, and we’ll map the long-lead items first.
Yes, and we’ve done it. An existing detached garage in 92404 can become a finished ADU with custom white oak cabinetry, stone counters, and architectural glass. The constraint isn’t the space, it’s the supporting systems: the old panel and aging plumbing often need upgrades before the finishes go in. We handle that sequencing so your design investment isn’t wasted. Call (866) 808-7312 and we’ll walk the garage with you.
We spec dual-pane low-E glass with thermally broken frames, and we size window placement for shade and cross-ventilation on San Bernardino’s single-story lots. On the northern edges near the mountain foothills, like parts of 92407, we also account for Santa Ana wind exposure with heavier-rated framing. Windows are one of the few places where upgrading early pays off every summer. Call (866) 808-7312 if you want us to review your plan’s window schedule.
Yes. We install Boxabl units on sites where a factory-built studio makes financial sense, and we work with Mighty Buildings for larger modular projects. In the 92405 neighborhood off Valencia Drive, our crew built a detached ADU with James Hardie siding, a custom white oak island, and Cover’s thermally broken glass system, but the real story was the six-month lead time on the imported Italian tile and the custom steel door. We locked the price in writing before releasing the millwork order, and the homeowner avoided a mid-project surprise when lumber prices spiked. Call (866) 808-7312 for a prefab-vs-stick-frame comparison on your lot.
We handle it from first submittal to final inspection. San Bernardino has streamlined its ADU permits over the last few years, but high-end projects with custom engineering still require careful submittal sequencing. We pull permits, we respond to plan-check comments, and we pass inspections. You’ll get the same fixed-price protection on the permit phase as on the construction, and a written line-item quote before we submit anything. Call (866) 808-7312 and ask for Neil. He’ll tell you what your specific project will face at the counter.
Written by Neil Stratton, Owner at Cottage ADU Builders, serving San Bernardino and the Inland Empire.