Should You Build an ADU? What It Actually Does to Your Home's Value in the Sacramento Region

Quick answer: An accessory dwelling unit (ADU) can add meaningful value to a Sacramento-area home, but it rarely dollar-for-dollar matches your construction cost, and how much value it adds depends heavily on rental demand, lot configuration, and how an appraiser classifies the space. Below, we break down what local appraisal data says, what we've seen with our own clients in El Dorado Hills, Folsom, and greater Sacramento, and how to think about an ADU if you're considering one.

Written by Scott Ostrode and the Team Ostrode Properties team, serving El Dorado, Sacramento, Placer, and Yolo Counties.What Is an ADU, Exactly?

An accessory dwelling unit is a secondary living space on a residential lot that's built for independent living, meaning it has its own sleeping area, bathroom, and kitchen. It can be:

• Detached, like a converted garage or a standalone backyard unit
• Attached, built onto the side of the main house
• Internal, carved out of existing square footage like a basement or bonus room

According to the Sacramento Appraisal Blog, run by longtime Sacramento-region appraiser Ryan Lundquist, the exact definition of an ADU can vary somewhat by city and county, though California and Sacramento County both generally require that independent-living setup. That distinction matters more than most homeowners realize, because it's the difference between a "bonus room" and a legally recognized second unit.

Does an ADU Actually Increase Home Value?

This is the question we get asked constantly, and the honest answer is: it depends, but usually yes, just not as much as the build cost.

Lundquist's research on the Sacramento Appraisal Blog notes that because comparable sales with ADUs can be limited, appraisers sometimes have to look back through years of neighborhood sales to find a legitimate comp. He's also pointed out a pattern worth knowing before you break ground: appraisers accustomed to conservative lender-driven valuations have historically undervalued ADUs relative to their rental income and construction cost, though he adds that in our region, the growing number of accessory units on the market has actually made it easier for appraisers to support stronger value conclusions instead of defaulting to overly cautious numbers.

For perspective on the ceiling of that value, Lundquist has referenced a Working RE magazine study out of Portland finding that ADUs contributed somewhere between roughly a quarter and nearly half of a property's total value in some cases. That's a wide range, and it's exactly why "just build one, it'll pay for itself" isn't advice we give without context.

Key factors that move the needle on ADU value

1. Rental demand in your specific neighborhood. A higher-rent market supports a more valuable ADU than an area with soft rental demand.
2. How it's used. The appraisal community generally hopes ADUs go toward long-term rentals rather than short-term Airbnb-style use, since that's what supports sustainable local value and housing supply.
3. Whether it's attached or internal. Per the Sacramento Appraisal Blog, when an ADU is carved out of the main house (a converted floor or wing), appraisers often have to subtract that square footage from the primary home's gross living area (GLA) and treat it as a separate line item, rather than just adding it to the home's total size.
4. Condition and permitting. An unpermitted or poorly built unit can create appraisal and lending headaches down the line, even if it "shows" fine to a buyer walking through.

2026 Update: Fannie Mae Now Allows Multiple ADUs

This is a genuinely big shift, and most homeowners haven't heard about it yet. As of March 31, 2026, Fannie Mae now allows multiple ADUs on one-unit properties, and it allows an ADU on multi-unit properties as long as the total door count does not exceed four. This new policy is part of the Selling Guide's UAD 3.6 Policy Supplement, and it only applies to lenders using the UAD 3.6 appraisal format, which is becoming mandatory industry-wide by November 2026.

Here's the nuance that matters for value: even though multiple ADUs are now financeable, the market still doesn't automatically treat these properties as small income residential, meaning triplexes or fourplexes. Most of the time, buyers and appraisers still view a main home with one or two ADUs as a single-family home with accessory living space attached, not as a multi-unit investment property. The main exception tends to show up on small acreage residential properties, where the numbers occasionally work out differently.

Practically speaking, a main home with multiple ADUs on a typical suburban lot is not the same animal as a true triplex or fourplex, and it usually shouldn't be priced or comped that way. An investor generally isn't going to pay a premium for extra acreage just to end up with a triplex on five acres. That math rarely pencils out.

Why are so many homeowners building ADUs right now?

A lot of it comes down to affordability. Building a full-size new home in California increasingly comes with solar requirements, all-electric mandates instead of gas, Mello-Roos taxes, and HOA fees stacked on top, and for a lot of buyers, that combination is simply a non-starter. An ADU lets a family add living space, housing for aging parents, or rental income without taking on a brand-new construction package loaded with those extra costs.

Worth keeping in perspective: this trend probably won't run forever. Not every buyer wants the extra car parking and density that comes with more accessory units on a lot, and at some point the market and local zoning rules will likely temper how far this goes. For now, though, ADUs remain one of the more realistic paths to adding space and value in a market where a traditional move-up home has gotten harder to pencil out.

Is My Pool House or Guest Room Actually an ADU?

Not necessarily, and this trips people up more than you'd think. Per Sacramento Appraisal Blog guidance, a structure only qualifies as a true ADU if it has a sleeping area, a bathroom, and a kitchen. A pool house with a bathroom but no kitchen is still just a pool house from a valuation standpoint, no matter what the listing calls it.

This matters at listing time too. If your county tax records or your MLS listing includes ADU square footage in the home's total size, make sure it's clearly disclosed. Otherwise you risk pricing a home in a way that doesn't match how an appraiser, or a savvy buyer's agent, will actually evaluate the property.

FAQ: ADUs in Sacramento, El Dorado Hills & Placer County

Q: How much value does an ADU add to my home? A: There's no flat percentage. Local appraisal data suggests it can range widely, often somewhere between roughly a quarter and half of total property value in strong rental markets, and less in areas with weaker rental demand. The safest approach is to have a local agent or appraiser pull recent comps with ADUs in your specific neighborhood.

Q: Will an ADU be counted in my home's official square footage? A: Usually not automatically. Detached ADUs are typically valued as a separate line item rather than added straight into your home's gross living area. Attached or internal ADUs are more nuanced and depend on how the space is configured and accessed.

Q: Can I use my ADU as a short-term rental? A: Check your city or county's zoning rules and any HOA/CC&R restrictions first. Some areas restrict rental use of accessory units, and long-term rental use is generally viewed more favorably by appraisers and local housing policy alike.

Q: Is building an ADU a good investment in the Sacramento region? A: For many homeowners, yes, especially where rental demand is strong and the ADU is permitted and well-built. But it's rarely a dollar-for-dollar return on construction cost, so it's worth running the numbers with a local real estate professional before you commit.

Q: What's the difference between an ADU and a JADU? A: A JADU (junior accessory dwelling unit) is a smaller unit, generally created within the walls of the existing home, often sharing some systems with the main house, while a full ADU is a more independent unit, whether attached or detached.

Q: Does Fannie Mae allow homes with multiple ADUs? A: Yes, as of March 31, 2026. One-unit properties can now have multiple ADUs, and multi-unit properties can include an ADU as long as the total door count does not exceed four. This is part of Fannie Mae's UAD 3.6 Policy Supplement and only applies to lenders using the UAD 3.6 appraisal format. That said, the market still generally treats these as single-family homes with accessory units, not as small triplexes or fourplexes, except in some small acreage cases.

Thinking About an ADU? Let's Talk Numbers First

Before you spend a dollar on permits or design, it's worth having a conversation about what an ADU would realistically do for your specific property and neighborhood. Scott Ostrode and the Team Ostrode Properties team work with homeowners across El Dorado Hills, Folsom, Sacramento, Placer, and Yolo Counties every day on exactly this kind of decision.

Reach out to Team Ostrode Properties for a no-pressure conversation about your home's value, ADU potential, or selling plans.

Scott Ostrode

DRE 01241383

Scott@TeamOstrode.com

916-799-1662

TeamOstrode.com 

Sources: Ryan Lundquist, Sacramento Appraisal Blog: "The Skinny on Accessory Dwelling Units" and "How to Figure Out What an Accessory Dwelling Is Worth." Content referenced with attribution per the Sacramento Appraisal Blog's sharing policy; original analysis and opinions belong to Ryan Lundquist.

This article is for general informational purposes only and is not a substitute for a formal appraisal or legal/zoning advice specific to your property.