ADU Design & Permitting Cost — Plans, Permits & Build, One Fixed Price

How Much Does ADU Design & Permitting Cost in Highland?

Design and permitting for an accessory dwelling unit in Highland typically runs $6,500 to $18,000 for a standard detached unit, with most homeowners landing around $9,000 to $13,000 all-in. That covers architectural drawings, structural and Title 24 energy calcs, and the city plan-check fees, but not construction. The number moves with unit size, lot slope, and whether you’re building from a prefab platform or a custom plan.

We’re Sunburst ADU Builders, and we’ve walked Highland homeowners through enough plan reviews to know where the money actually goes. Here’s the honest breakdown, including the local costs most guides skip.

Key Takeaways

• Full design and permitting on a detached ADU in Highland: $6,500 to $18,000, typically $9,000 to $13,000.
• City plan-check and permit fees alone run $2,800 to $5,500 depending on square footage.
• Design alone (drawings, structural, energy) is usually $3,500 to $9,500.
• Prefab platforms like Abodu, Cover, and Plant Prefab often supply their own plans, which can trim design fees by $1,500 to $4,000.
• Hillside lots and non-standard setbacks are the two biggest cost-lifters in Highland.

ADU Design & Permitting Cost Breakdown (2026)

Here’s what Highland-area homeowners are actually paying line by line. These are design-and-permitting figures only. Construction is a separate budget, and we cover that in our full ADU Design & Permitting in Highland guide.

What pushes a Highland project toward the top of that range? Sloped lots, units over 1,000 square feet, and anything that needs a variance. What pulls it down? Using a prefab platform whose manufacturer already holds pre-approved California plans. When we work with a brand like Cover or Plant Prefab, we’re often able to reuse their engineering package, which shaves real money off the design line and shortens plan review.

If you want the construction side of these numbers too, see our home overview and the city-specific build guides below.

What Affects ADU Design & Permitting Pricing in Highland

No two Highland lots price the same. These are the factors that move the needle most, and most of them are specific to how this part of San Bernardino County is laid out.

1. Lot slope and grading complexity

Highland has more hillside parcels than most buyers expect. A unit that needs a retaining wall or pier-and-beam foundation adds structural engineering time and often a soils report, which together can add $1,500 to $3,000 to your design budget before a single permit fee is paid.

2. Detached vs. attached vs. conversion

A garage conversion or an attached unit usually permits faster and cheaper than a fully detached structure. Detached units trigger more site work, separate utility runs, and more inspections. Budget the design phase about 15% to 25% higher for detached.

3. Unit size and story count

City fees scale with square footage, and a two-story unit needs more structural work and a second-story framing review. A 600-square-foot studio is a fundamentally cheaper permit than a 1,200-square-foot two-bedroom. If your goal is rental income, the math on size usually favors the smaller unit anyway.

4. Build method (prefab vs. custom stick-built)

This is where the range opens up most. Prefab and modular platforms like Abodu, Dvele, or Mighty Buildings ship with much of the design and engineering already done, which can cut design fees significantly. A fully custom stick-built unit gives you more freedom but pays for every drawing from scratch.

5. Setbacks, easements, and utility conflicts

Existing utility easements or a tight rear setback often force layout changes during design, which means resubmittals. A site survey up front usually catches these early and saves you the back-and-forth later.

6. City of Highland plan-check timeline

Plan review often stretches longer than homeowners expect. California’s ADU rules have sped up approval in many cases, but a complex or hillside project still takes longer. A cleaner permit set means fewer review cycles, and fewer review cycles is where you actually save money on the design side.

How to Save on ADU Design & Permitting in Highland

None of these are tricks. They’re the levers that actually lower the number.

• Start with a platform that has pre-engineered California plans. When a manufacturer already holds approved plans, you’re not paying an architect to reinvent them. We work across Abodu, Cover, Dvele, Mighty Buildings, Boxabl, and Plant Prefab, so we can compare which one fits your lot and your budget rather than steering you to a single brand.
• Get the site survey done first. It’s a $500 to $1,200 line item that prevents a $1,500 resubmittal. Skipping it is the most common way Highland homeowners spend more than they needed to.
• Design for the standard, not a variance. Every variance adds time and fees. A good designer works the setbacks and height limits into the first draft.
• Bundle your interior finish plans. Since we also handle kitchen and bathroom remodeling, you can plan the ADU’s interior fit-out in the same design pass instead of paying a second firm later. From foundation to finished kitchen, it’s one team and one contract.
• Ask about our free estimate. We’ll walk your lot and give you a real design-and-permitting number before you commit to anything. Call (855) 676-6807.

Why Design & Permitting Costs More in Highland Than the State Average

Across California, design and permitting for an ADU averages around $8,000 to $15,000. Highland sits at the upper-middle of that band. The reason is the terrain: this is hill-and-desert-edge country, and much of it isn’t flat. A flat lot in a valley subdivision is the cheapest possible permit scenario. A sloped lot off a Highland trail-adjacent street is the opposite. The gap between those two can be several thousand dollars on design alone.

We help homeowners understand where their specific lot falls before they spend anything. The right ADU for your lot, your budget, and your timeline, not the only one we carry.

Design & Permitting vs. Construction: What the Total Project Actually Costs

It helps to see design and permitting next to the full build, because people sometimes confuse the two numbers. Design and permitting is $6,500 to $18,000. Construction for a detached ADU in Highland typically runs $120,000 to $320,000 depending on method and size, with prefab and modular units at the lower end and custom on the higher end.

When you add a turnkey interior finish (kitchen and bathroom), you should plan for that as its own line. If you want a prefab unit delivered and finished, the platform handles the shell and we handle the interior. That’s the difference between buying a box and getting a finished, rentable unit.

What’s Included in the Sunburst Design & Permitting Scope

When you work with us, the design and permitting phase covers more than a set of drawings. Here’s the scope:

• Site assessment and lot-fit analysis, including slope and utility checks
• Architectural drawings coordinated with your chosen build method
• Structural engineering and Title 24 energy compliance
• Site survey and, where needed, geotechnical coordination
• Plan set assembly for City of Highland submittal
• Plan-check response management through approval
• Interior finish planning for kitchen and bath, so the unit is turnkey

Exterior work on the finished unit uses James Hardie fiber-cement siding because your ADU is a long-term asset, not a temporary structure. That material decision gets made during design, not after, because it affects the plans.

Which ADU Brand Should You Design Around?

This is the question most Highland homeowners get stuck on, and it’s the right one to ask. The brand you choose affects your design cost, your timeline, and your total build. Here’s how the major platforms differ in the design-and-permitting phase:

• Abodu: A finished, turnkey unit with much of the design work already done. Strong when you want speed and don’t need a custom layout.
• Cover: Energy-efficient panels and a design-forward approach. Works well on tighter lots.
• Dvele: Higher-performance, prefab modular units. Design coordination is more involved but the finished product is substantial.
• Mighty Buildings: 3D-printed panel construction. The engineering package is a real advantage on design fees, and it’s a genuinely different build method.
• Boxabl: The foldable unit is the fastest to deploy and the most compact. Good for a single rental unit where space is tight.
• Plant Prefab: Flexible modular platform that can accommodate a range of layouts and finishes. Strong for a custom-touch prefab.

We also handle Tuff Shed conversions for homeowners who already have a structure on the lot that qualifies, which is often the cheapest possible path through design and permitting. Because we work with all of these, we can compare them side by side against your lot, your budget, and your timeline. That’s the whole point of being manufacturer-agnostic.

What About Kitchen and Bathroom Design in the ADU?

One cost homeowners forget: the interior. Design and permitting for the ADU structure is one thing, but if you want a finished kitchen and bathroom rather than a shell, those need drawings too. We handle kitchen remodeling and bathroom remodeling under the same roof, so those plans get coordinated with the ADU permit set instead of being handled by a separate firm months later. For a rental unit, this is the difference between a vacant shell and a finished unit a renter can move into.

Frequently Asked Questions

How much does ADU design and permitting cost in Highland?

Design and permitting for a standard detached ADU in Highland usually costs $6,500 to $18,000, with most projects landing between $9,000 and $13,000. City plan-check fees alone are $2,800 to $5,500. Call (855) 676-6807 for an exact quote, free of charge.

How much are Highland ADU permit fees specifically?

City of Highland plan-check and permit fees typically run $2,800 to $5,500 for a residential ADU, scaling with square footage and the number of required inspections. School district and utility fees add roughly $300 to $1,200 on top. Prefab platforms sometimes reduce inspection counts, which can lower this slightly.

Is it cheaper to design a prefab ADU or a custom one?

Prefab is usually cheaper through the design phase, often $1,500 to $4,000 less, because the manufacturer already holds engineered plans you can reuse. A fully custom stick-built unit pays for every drawing and calculation from scratch, which is worth it if your lot is unusual or your layout is non-standard. Call us and we’ll give you a straight comparison for your lot.

Can I get my ADU plans approved faster in Highland?

Yes, usually by having a complete, clean permit set ready for the first submittal. Fewer plan-check cycles saves both time and money, often $0 to $1,500 in resubmittal fees alone. Using a platform with pre-engineered California plans is the single biggest time-saver. We handle the submittal and the plan-check response so you’re not the one tracking it down.

Do I need a separate architect if I use a prefab ADU brand?

Usually not for the structure, because the platform supplies its own engineered plans. You may still need limited local design work for site adaptation, utility connections, or interior finish, which is typically $1,000 to $3,000. We coordinate that local work with the brand’s engineering so your ADU gets their engineering and our local build expertise.

Ready for a Real Number on Your Highland Lot?

The ranges on this page are what Highland homeowners actually pay. Your exact number comes down to your lot, your chosen build method, and the size of the unit you want. We’ll walk the property, look at the slope, check the setbacks, and give you a specific design-and-permitting estimate before you commit to anything. No pressure, no one-size-fits-all pitch. That’s what a free estimate means with us.

Call (855) 676-6807 to schedule your free estimate. We’ll help you compare your options across prefab, modular, and custom before you commit.

Pricing reflects the Highland market as of 2026. Sunburst ADU Builders offers free estimates – call (855) 676-6807.