Best ADU For · 2026
Best ADU for Adult Children: Which Model Wins
For most families bringing an adult child back home, the Six Sixty is the clear winner: a 660 sq ft, one bedroom, one bath ADU priced at $287,000 with a permitting budget already built in. It gives your son or daughter a real front door, a real kitchen, and a real bedroom, without turning your backyard into a construction project that drags on for a year. If they need more room to spread out, whether that’s a partner moving in with them or a home office alongside the bedroom, the Eight Eighty-Five 2BR takes over as the better fit.
The short version: The Six Sixty (660 sq ft, 1 bed, 1 bath, $287,000) is the best all-around ADU for an adult child moving back home. It delivers full independence in a manageable footprint with a 5-month build. Families who need more space, for a returning couple, a new grandchild, or a dedicated workspace, should look at the Eight Eighty-Five 2BR ($377,000). Parents on a tighter lot or budget can start with the Five Five Five ($267,000).
Why housing an adult child needs a different kind of ADU
An adult child moving home is not a guest. They’re an adult with their own routine, their own income (or the plan to get one), and their own need for a door that closes. A converted garage or a spare bedroom inside the main house rarely works long term, because it keeps them living under someone else’s roof rules by default. What actually solves the problem is a separate structure with its own kitchen, its own bathroom, and its own entrance, so everyone in the household gets real privacy again.
That’s a different design brief than a rental ADU or a backyard office. The unit needs to feel like a real home, not a studio apartment they’re passing through. A full kitchen matters more here than it does for a short-term rental, because your child is going to cook dinner in it most nights. A washer and dryer hookup matters. So does having enough square footage that the space doesn’t feel like a dorm room once they’ve moved their life into it.
At the same time, most parents don’t want to overbuild. The goal is usually a launchpad, not a permanent second household, so the smartest pick balances real independence against a price and timeline that make sense for a few years of use, not necessarily a forever home.
The models that fit
| Model | Size | Beds/Baths | All-inclusive price* | Why it fits |
|---|---|---|---|---|
| Five Five Five | 555 sq ft | 1 bed / 1 bath | $267,000 | Smaller footprint and the lowest price of the group, a solid starter option for a single adult child or a tighter lot |
| Six Sixty | 660 sq ft | 1 bed / 1 bath | $287,000 | The all-rounder, purpose-built for parents, adult children, and rental income. Full independence without overbuilding |
| Eight Eighty-Five 2BR | 885 sq ft | 2 bed / 1 bath | $377,000 | Room to grow into: a returning couple, a grandchild, or a second bedroom for a home office |
*Includes a permitting budget, not final permit costs. Permits and property-specific site work (septic, retaining walls, etc.) vary by property and are confirmed in your feasibility study.
See the full lineup at /models/ to compare every layout side by side.
The top pick: the Six Sixty
The Six Sixty is Framework First’s most popular model, and for adult children moving home, it’s usually the right call. At 660 sq ft with one bedroom and one bath, it’s big enough for a genuinely comfortable one-person (or one-couple) household: a real bedroom separate from the living space, a full kitchen instead of a kitchenette, and enough square footage that it doesn’t feel like they’re camping in the backyard.
It also builds fast. At 5 months from signed contract to move-in, it’s quicker than the larger two-bedroom models, which matters if your child needs a place to land sooner rather than later. And because the $287,000 price already includes a permitting budget along with plans, the foundation, the factory build, delivery, utility hookups, appliances, and final inspection, there’s no separate bidding process to manage on top of it. Exact permit costs are set by your city and get confirmed during your feasibility study. You sign one contract and Framework First handles the rest, roughly 97% of the build happening off-site in the Salinas factory before it’s crane-delivered to your property in a single day.
The runner-up: the Eight Eighty-Five 2BR
If your adult child’s situation involves more than just themselves, a partner moving in, a baby on the way, or a genuine need for a second room to use as an office, the Eight Eighty-Five 2BR is the better fit. At 885 sq ft with two bedrooms and one bath, it gives them the extra room to grow into without jumping all the way up to a three-bedroom model. It runs $377,000, permitting budget included, with a 6-month build timeline, a meaningful step up from the Six Sixty in both price and space, but it buys real flexibility for multigenerational households where the arrangement might last years rather than months.
For parents working with a smaller lot or a tighter budget who still want their child to have a fully independent space, the Five Five Five is worth a look too. At 555 sq ft and $267,000, it’s the most affordable one-bedroom option in the lineup and still includes a full kitchen and bath, just in a more compact footprint.
Pricing, financing, and next steps
Every model above includes the full build and a permitting budget, so there’s no per-square-foot guessing game once the crane shows up. Actual permit costs are set by your city and confirmed in your feasibility study, and any property-specific site work, like septic upgrades or retaining walls, is handled in-house under your contract rather than folded into the listed model price. To see what a specific model would cost with your financing scenario, run the numbers through the ADU cost calculator. If you’re not sure your lot can actually support an ADU yet, especially setbacks, utility access, and site conditions, a feasibility study answers that before you commit to a model. And for the full breakdown of what’s included in every price, visit the pricing page.
Frequently asked questions
What’s the best ADU size for an adult child moving back home?
For one adult (or one couple) with no kids yet, 555 to 660 sq ft is usually the sweet spot. That’s enough space for a real bedroom, a full kitchen, and a living area without paying for square footage that goes unused. The Six Sixty (660 sq ft, $287,000) is the most popular choice for exactly this reason.
Should I get a one-bedroom or two-bedroom ADU for my adult child?
Start with what their situation actually looks like today, and what it might look like in the next couple of years. A one-bedroom like the Six Sixty works well for a single adult child or a couple with no plans to grow the household. If a baby, a roommate, or a home office is realistically on the horizon, the Eight Eighty-Five 2BR (885 sq ft, two bedrooms, $377,000) gives you that extra room without overbuilding into a three-bedroom unit.
How fast can Framework First build an ADU for my adult child?
Timelines depend on the model. The Five Five Five and Six Sixty both build in about 5 months from signed contract to move-in. The Eight Eighty-Five 2BR takes about 6 months. Because roughly 97% of the build happens in the Salinas factory before delivery, timelines stay predictable compared to a traditional site-built addition.
Does the ADU price include everything, or are there extra costs later?
The listed price already includes a permitting budget along with plans, the foundation, the factory build, delivery, utility hookups, appliances, and final inspection. There’s no separate line item for a kitchen or bathroom finish package, and no per-square-foot pricing to calculate. The one exception is anything property-specific, like your exact permit fees or site work such as septic upgrades or retaining walls; those are confirmed during your feasibility study and, when needed, built into your contract so the project still stays with one builder. If you want to confirm what a specific model would run for your property, the ADU cost calculator is the fastest way to check.
Can an ADU built for an adult child later become a rental?
Yes. That’s one of the practical advantages of building instead of converting a room in the main house. Once your child moves out, a one-bedroom unit like the Six Sixty or a two-bedroom like the Eight Eighty-Five 2BR can shift into a long-term rental or a space for aging parents, without any structural changes. The independence built in for your child (separate kitchen, separate entrance) is the same thing that makes the unit valuable as a rental later.
Ready to see which model fits your lot and your family? Start a feasibility study or browse the full model lineup to compare every layout side by side.