Does Building an ADU Increase Your Home's Value?
- Jul 1
- 5 min read
Does building an ADU increase your home's value? The short answer is yes — and the numbers are more compelling than most homeowners expect. A well-built, fully permitted accessory dwelling unit in Cache Valley adds real appraised value, rental income potential, and buyer appeal that's increasingly difficult to replicate with any other single improvement. Here's an honest breakdown of what to expect in Northern Utah in 2026.
The Numbers
A well-built, fully permitted ADU typically increases property value by 20 to 35 percent according to national data from the National Association of Realtors. In high demand markets like Northern Utah where housing supply remains tight, that increase can be on the higher end of that range.
Here's how that plays out in real numbers. If your home is currently valued at $450,000 and you add a well-built ADU, you're potentially looking at $90,000 to $157,000 in added property value — before you factor in rental income or the impact of added square footage on the appraisal.
In markets where homes are selling at $400 to $500 per square foot, adding 500 square feet of finished ADU space can add $200,000 to $250,000 in appraised value based on square footage alone. That's a significant return on an investment that typically runs $150,000 to $250,000 for a well-built attached or detached unit in Cache Valley.
How Appraisers Actually Value ADUs in 2026
This is worth understanding in detail because it's more favorable than most homeowners realize.
Modern appraisal standards in 2026 have gotten significantly better at capturing ADU value. The Uniform Appraisal Dataset updated in recent years gives appraisers a clear, consistent framework for documenting ADUs — reducing the gap that used to exist between what an ADU cost to build and what it added to an appraisal.
Appraisers now consider multiple factors when valuing an ADU. They look at comparable sales of similar properties with ADUs in the area. They assess the unit type, size, layout, and privacy — a fully detached ADU with its own entrance and complete separation typically appraises higher than an attached unit of the same size. And importantly, they increasingly apply an income-based approach that accounts for the rental income potential of the unit — not just the square footage.
Your instinct that appraisers don't give credit for rental income was actually a more accurate description of how appraisals used to work. In 2026 that's changed. A permitted ADU with documented rental income potential is valued differently than raw square footage — and that difference works in your favor.
Does the Type of ADU Matter for Value?
Yes — and the differences are worth knowing before you decide what to build.
Detached ADUs tend to add the most value per square foot. A fully standalone structure with its own entrance, complete privacy, and independent systems is what appraisers and buyers respond to most strongly. Detached units also command the highest rental rates in the market which further supports their appraised value under the income approach.
Attached ADUs still add meaningful value — they add legal square footage that appraisers calculate similarly to the main home. However most Utah jurisdictions cap attached ADUs at around 50 percent of the main home's square footage, which limits how much you can add. A 600 square foot attached ADU on a 1,200 square foot home is at the ceiling for many municipalities.
Garage conversions are the most cost-effective path since the structure already exists, but the value added depends heavily on finish level and whether the unit functions as a true independent living space with a full kitchen and bathroom.
Within any type — a unit with a full kitchen and bathroom adds more value than a unit without one. A complete, livable space is what unlocks both the appraised value increase and the rental income potential that modern appraisals recognize.
When an ADU Might Not Add the Value You Expect
There are situations where an ADU doesn't perform the way a homeowner expects — and it's worth being straight about them.
The biggest one is permitting. An ADU that isn't fully permitted, wasn't built to current code, or doesn't have proper documentation creates problems at appraisal and at resale. Buyers, lenders, and appraisers are increasingly sophisticated about what a legal ADU looks like on paper. An unpermitted unit can actually create liability rather than value.
Over-improving for your neighborhood is the second consideration — the same principle that applies to any remodeling project. If your ADU pushes your home's total value significantly beyond what comparable homes in your area are selling for, you may not fully recoup the investment at resale. This is more of a concern in lower-priced neighborhoods than in Cache Valley's mid-to-upper range markets where ADU demand is strong.
The Honest Framework
Here's something worth saying plainly — and it echoes what we say about home additions generally.
If you're building an ADU you're almost certainly planning to stay in your home for a long time. You're doing it for your life — rental income, multigenerational living, housing flexibility — not purely for the resale number.
And when that's the case, the return you get every day matters more than the percentage you'd recoup at resale. A well-built ADU that generates $1,500 a month in rental income pays for itself over time regardless of what an appraisal says on any given day.
The buyer perspective is also worth noting. It's genuinely hard to find a buyer who doesn't want a separate living space on their property — especially in a market like Cache Valley where housing costs have climbed and multigenerational living is increasingly common. A legal, well-built ADU makes your home more competitive the moment it hits the market, not less.
Frequently Asked Questions
How much does an ADU increase home value in Utah?
On average a well-built, fully permitted ADU increases property value by 20 to 35 percent. In Northern Utah where housing demand remains strong and square footage is valued highly, returns tend to be on the stronger end of that range. The actual increase depends on the type of ADU, the size, the finish level, and how the local market values comparable properties with ADUs.
Do appraisers in Utah give credit for rental income on an ADU?
Yes — increasingly so. Modern appraisal standards in 2026 allow appraisers to apply an income-based approach to ADU valuation alongside the standard square footage comparison. A permitted ADU with documented rental income potential is valued more favorably than raw square footage alone. This is a meaningful shift from how ADU appraisals worked even a few years ago.
Does an unpermitted ADU add value to a home in Cache Valley?
Not reliably — and it can create problems. Buyers, lenders, and appraisers are increasingly aware of what a legal ADU looks like on paper. An unpermitted unit may not be recognized in an appraisal and can create liability at the time of sale. If you're building an ADU the permit and inspection process is non-negotiable — it's what makes the unit legal, insurable, and recognized at resale.
