How Much Does a Garage Conversion ADU Cost in Highland?
A garage conversion ADU in Highland typically runs $65,000 to $140,000 in 2026, with most homeowners landing between $85,000 and $115,000 for a standard one-car or two-car garage turned into a livable studio or one-bedroom unit. That figure includes permits, mechanical rough-in, insulation, drywall, flooring, a kitchenette, and a bathroom. If your garage is detached, on a slope, or needs a new foundation, add $15,000 to $40,000 for site work specific to Highland’s soil and grading conditions.
We’re Sunburst ADU Builders, and garage conversions are the fastest and least expensive way to add a rentable unit to a Highland property. The reason is simple: the shell already exists. You’re not pouring a new slab or framing a roof from scratch. What you’re doing is re-engineering an unfinished box into a code-compliant dwelling, and the cost depends on how much of that box needs help. This guide breaks down the real numbers so you can plan with confidence, not guesswork.
Key Takeaways
- Most Highland garage conversions land between $85,000 and $115,000 for a finished, permitted unit.
- Line-item costs range from $65,000 (minimal studio) to $140,000+ (full one-bedroom with premium finishes).
- City of Highland permits, plan review, and impact fees run roughly $4,500 to $9,000 depending on unit size.
- Detached garages and slope-adjacent lots add $15,000 to $40,000 in foundation and site work.
- Prefab and modular options can compress timelines but rarely beat a conversion on total cost.
Garage Conversion ADU Cost Breakdown (2026)
Here’s how a typical 400 to 500 square foot Highland garage conversion breaks down by line item. These ranges reflect materials and labor in the Inland Empire market as of early 2026.
| Line Item | Typical Cost Range | Notes |
|---|---|---|
| Architectural plans & engineering | $3,500 – $7,500 | Stamped plans required for city submittal; includes structural and Title 24 |
| City permits & impact fees | $4,500 – $9,000 | Highland plan review, school fees, and utility connection |
| Foundation & slab work | $4,000 – $18,000 | Depends on whether existing slab is sound and whether the garage is detached |
| Framing modifications | $5,000 – $14,000 | Garage door infill, new windows, door openings, ceiling height adjustments |
| Electrical (panel, circuits, fixtures) | $6,000 – $12,000 | Sub-panel or panel upgrade often required for a dwelling unit |
| Plumbing (bath, kitchenette, water heater) | $7,000 – $15,000 | Trenching to main line adds cost if garage is detached |
| HVAC & insulation | $6,000 – $12,000 | Mini-split systems common in Southern California; Title 24 compliance |
| Drywall, paint, flooring | $8,000 – $16,000 | Standard finishes to mid-grade; luxury vinyl plank and tile typical |
| Kitchen & bathroom finishes | $10,000 – $22,000 | Cabinets, counters, fixtures, tile; scale depends on rental vs. family use |
| Exterior (siding, roof patches, trim) | $3,500 – $9,000 | We specify James Hardie fiber-cement siding for durability and warranty coverage |
| Fire separation & life safety | $2,000 – $5,000 | Smoke/CO detectors, egress windows, fire-rated wall between house and unit |
Total range: $65,000 to $140,000. A lean studio conversion with basic finishes can come in near $65,000 to $80,000. A one-bedroom with a full kitchen, upgraded bathroom, and detached garage site work pushes past $130,000. The gap between those two numbers is almost entirely about scope and site conditions, not about which contractor you hire.
We work across prefab and modular platforms too, and we’ll be direct with you: a garage conversion is almost always cheaper than a new prefab unit placed in the backyard. Companies like Abodu, Cover, and Mighty Buildings make excellent products, but their all-in costs (including delivery, crane, foundation, and utility connections) generally land $120,000 and up for a comparable square footage. If you’re weighing options, we’ll help you compare a conversion side by side with a prefab build before you commit to either. That’s the whole point of having access to six manufacturers plus custom stick-built and conversion work under one team.
What Affects Garage Conversion ADU Pricing in Highland
- Garage age and condition: A lot of Highland’s housing stock dates to the 1980s and early 1990s, when builders poured thinner slabs and used garage framing that wasn’t designed for habitable space. If your slab has cracks or the ceiling joists are undersized, we’re reinforcing before we finish. That adds $5,000 to $15,000, but it’s non-negotiable for a signed-off permit.
- Attached vs. detached garage: An attached garage is the simpler and cheaper conversion because plumbing and electrical can tie into the house with short runs. A detached garage means trenching utilities, running gas lines if you want them, and often adding a separate heating/cooling system. That’s a $15,000 to $30,000 spread on its own.
- Slope and soil on the lot: The east Highland areas near the base of the foothills deal with grading issues that flat-lot neighborhoods don’t. If your garage sits on fill soil or a graded pad, a geotechnical report and possibly new foundation work are needed. Budget $8,000 to $20,000 for site corrections on hillside properties.
- Electrical service capacity: An ADU needs its own sub-panel or a service upgrade. If your existing main panel is already at capacity, a full upgrade to 200-amp service runs $3,500 to $7,000 on top of the interior electrical work. Older Highland homes with 100-amp panels frequently need this.
- MEP routing distance: The farther the new bathroom and kitchenette sit from the house’s existing water heater and drain lines, the more plumbing labor. Running a new tankless water heater for the ADU is often the cleaner and cheaper solution than trying to extend the main line, and it costs $2,500 to $4,500 installed.
- Whether you finish the interior yourself or not: The single biggest swing. A rental-grade finish (durable flooring, painted cabinets, builder fixtures) saves $15,000 to $25,000 over a custom in-law suite finish. Decide upfront who’s living here and let that drive the finish level.
One local factor that surprises Highland homeowners: the City of Highland’s plan review timeline. Conversion projects with complete, stamped plans typically clear review faster than ground-up new construction, but incomplete submittals can sit for weeks. We build the review time into the schedule from day one, so the permit period doesn’t stall the job.
How to Save on Garage Conversion ADU Costs
The biggest savings on a Highland garage conversion don’t come from cutting corners on the parts you can’t see. They come from smarter sequencing and honest scope decisions.
- Keep the existing footprint. Any structural change that expands the garage means new foundation work and new framing. Staying inside the existing walls is the single largest cost saver available.
- Don’t move the plumbing farther than you have to. Placing the bathroom and kitchenette along the wall closest to the house’s existing water and drain lines can save $3,000 to $6,000 in trenching and labor.
- Choose a tankless water heater over extending the main line. Cheaper to install, simpler to permit, and it gives the ADU tenant their own hot water supply.
- Pick rental-grade finishes deliberately. Luxury vinyl plank, painted MDF cabinets, and standard fixtures hold up well and cost significantly less than custom.
- Bundle kitchen and bathroom remodeling into the same contract. Since we do the ADU construction and the interior finish work under one roof, there’s no gap where a separate contractor waits on the framing crew. One team, one contract, fewer change orders.
- Get a fixed-scope estimate early. The biggest budget killer is discovering after demolition that the slab or wiring needed replacement. We assess that before the contract is signed. Call (855) 676-6807 for a free estimate; we’ll give you a real number, not a range that shifts after you’ve committed.
Some homeowners ask whether a prefab garage unit or a Tuff Shed conversion is cheaper than a full garage conversion. It can be, in a narrow set of cases, but only if the existing structure is already suitable. In most Highland garages, the upgrades needed to bring an old shell to dwelling standard narrow that gap considerably. We’ll run that comparison for you honestly. Prefab, modular, or custom: we help you compare before you commit.
Is a Garage Conversion ADU Worth It in Highland?
Yes, for most Highland homeowners it pencils out. A one-bedroom ADU in Highland rents in the range of $1,600 to $2,000 per month in the current market, depending on condition and location. Against a mid-range conversion cost of $100,000, that’s roughly a five- to six-year payback on rental income alone, before you count the property value lift.
The caveat is the build quality. A conversion built on a patched slab with undersized wiring will generate repair calls and vacancy. A conversion built to spec, with proper insulation, a code-compliant electrical panel, and durable exterior siding like James Hardie, holds its value and its rent. We specify James Hardie not because it’s the cheapest option but because your ADU is a long-term asset, not a temporary structure. The difference shows up in year eight, not year one.
If you’re also planning to update the main house, we handle kitchen remodeling and bathroom remodeling as part of the same scope, which is common when homeowners are preparing a property for a family member to move in or for a full rental arrangement.
Why We Handle Garage Conversions Differently
Most contractors who offer garage conversions either build everything from scratch or they’re dealer-locked to one prefab brand. We’re neither. Sunburst ADU Builders works across Abodu, Cover, Dvele, Mighty Buildings, Boxabl, and Plant Prefab, and we also build traditional stick-built and conversion projects. That means we’re matching you to the right ADU for your lot, your budget, and your timeline, not the only one we carry.
For a garage conversion specifically, the manufacturer roster matters less than the execution. What matters is that the team that frames the walls also finishes the kitchen and installs the bathroom tile, so there’s no handoff gap and no finger-pointing when the schedule slips. That’s why we keep ADU construction, kitchen remodeling, and bathroom remodeling under one roof.
If you want to understand the full scope of what a conversion involves before you start calling builders, read our guide to Garage Conversion ADU in Highland. If you’re still in the research phase and comparing build methods, start at our home page to see the full range of what we build.
FAQs – Garage Conversion ADU Cost in Highland
How much does a garage conversion ADU cost in Highland in 2026?
Most Highland garage conversions cost $65,000 to $140,000, with the majority of projects landing between $85,000 and $115,000. The low end is a studio with basic finishes in a sound existing garage; the high end is a detached garage on a graded lot with upgraded kitchen and bath finishes. Call (855) 676-6807 for a free estimate on your specific garage.
Is a garage conversion cheaper than building a new ADU?
Yes, typically by $40,000 to $80,000. A new detached ADU in Highland runs $180,000 and up, including foundation, framing, roof, and full utility runs. A garage conversion reuses the existing slab, walls, and roof, which is why the savings are so large. Call (855) 676-6807 to compare both options for your property; estimates are free.
How long does the permit process take for a garage conversion in Highland?
Plan review typically runs 6 to 10 weeks for a complete submittal. Incomplete plans get kicked back and restart the clock, which is why we handle plan prep and submittal ourselves. Construction after permit approval takes another 10 to 16 weeks depending on scope. Call (855) 676-6807 to start the conversation now and get ahead of the timeline.
What’s the cheapest way to convert a garage to an ADU in Highland?
The cheapest path is keeping everything inside the existing footprint, placing the bathroom and kitchenette on the wall closest to existing plumbing, choosing rental-grade finishes, and using a tankless water heater instead of extending the main line. That approach can bring a conversion down near $65,000 to $80,000. Call (855) 676-6807 and we’ll walk you through which savings apply to your garage.
Does a garage conversion add value to a Highland home?
Yes, and current Highland listings reflect it. A permitted ADU adds to both rentable square footage and resale appeal, and buyers in this market treat a legal, signed-off unit as a distinct asset. The value lift depends on the appraiser and the neighborhood, typically $40,000 to $80,000 on top of the conversion cost. Call (855) 676-6807 to discuss what a conversion would mean for your property value and timeline.
Get a Real Number for Your Highland Garage
We don’t quote from a spreadsheet. The range on this page tells you what to expect; a walkthrough of your actual garage tells you what it’ll cost. We’ll assess the slab, the wiring, the plumbing distance, and the permit path, then give you a fixed-scope estimate before you commit to anything. Whether you’re still deciding between a conversion and a prefab unit, or you’re ready to pull plans, we’re the team that can show you the full landscape honestly. Call Sunburst ADU Builders at (855) 676-6807 for a free estimate.
Pricing reflects the Highland market as of 2026. Sunburst ADU Builders offers free estimates – call (855) 676-6807.
What Our Customers Say
"Every invoice was tied to a completed milestone, so I always knew what I was paying for."
— Henry Kim"Detached unit in the back yard. Utilities trenched, separate meter, and it passed final on the first inspection."
— Hector Torres"Unit came out great and the tenant is happy. The timeline ran long, largely because of how slow the city was on plan check, though a couple of the delays were scheduling on their end."
— Jodi Reed