Best ADU For · 2026
Best ADU for a Home Office: Which Model Wins
If you’re building a backyard office and nothing else, the Four Fifty is the model to build. At $180,000, with a permitting budget already built into that price, for 450 sq ft, it’s the smallest and most affordable model Framework First offers, and a dedicated work studio doesn’t need a bedroom, a second bathroom, or extra square footage you’ll never use. If you want the office to double as a guest space down the road, the 405 is the better call.
The short version: For a pure home office, build the Four Fifty ($180,000, 450 sq ft studio). If you want that same office to convert into a guest suite or future rental someday, size up to the 405 ($237,000, 405 sq ft with a real bedroom). Need room for client meetings or a small team, not just a desk? The Five Five Five ($267,000, 555 sq ft) gives you the extra square footage without turning into a full second home.
Why a home office needs a different kind of ADU
Most people shopping for an ADU are thinking about a rental unit, a place for aging parents, or a home for adult kids. A home office is a different problem. You don’t need a second kitchen setup that gets heavy use, you don’t need two bathrooms, and you almost certainly don’t need three bedrooms. What you do need is separation: a door you can close between “work” and “home,” good natural light, reliable power and internet, and quiet.
That means the calculus for a work-from-home ADU is backwards from a rental ADU. Instead of maximizing bedrooms and square footage to chase rent, you’re optimizing for the smallest, most efficient footprint that still feels like a real professional space. Every extra square foot you don’t need is money spent on a room you’ll walk past every day instead of using.
The other consideration is permitting and site constraints. A smaller structure is generally faster to build and easier to fit on a lot that already has a house, a driveway, and a yard you don’t want to lose. If your goal is a standalone office in the backyard, not a second home, the studio and one-bedroom end of the lineup is where you should be shopping first.
The models that fit
| Model | Size | Beds/Baths | All-inclusive price* | Why it fits |
|---|---|---|---|---|
| Four Fifty | 450 sq ft | Studio / 1 bath | $180,000 | The smallest, most affordable model. Built for a private studio for one, exactly the footprint a solo home office needs |
| The 405 | 405 sq ft | 1 bed / 1 bath | $237,000 | A real separated bedroom nook. Use it as an office now, a guest room or future rental later |
| Five Five Five | 555 sq ft | 1 bed / 1 bath | $267,000 | Roomier layout with space to break out a meeting corner or a second desk without feeling cramped |
*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.
All three are rectangle-footprint models, which tends to make them the most straightforward builds on a standard backyard lot.
The top pick: Four Fifty
The Four Fifty is the smallest thing Framework First builds, and for a dedicated home office that’s exactly the point. At 450 sq ft it’s a studio with one bath, which is officially built for first ADUs, small lots, aging-in-place, and a private studio for one, and a private studio for one is precisely what a work-from-home office is.
At $180,000, it’s also the lowest entry point into the entire lineup, and that price already includes a permitting budget along with plans, the foundation, the factory build, delivery, utility hookups, and final inspection. Your exact permit costs depend on your city and get confirmed in your feasibility study. You’re not paying for a kitchen you’ll barely use or a second bathroom that sits empty. You’re paying for one clean room with its own entrance, on a 4 month build timeline, which is the fastest turnaround of any model Framework First offers.
If your goal is simply “I need to get out of my kitchen table and into a real office,” the Four Fifty is the model built for exactly that problem, at the lowest possible price point.
The runner-up: The 405
The 405 makes sense if you want more flexibility than a pure studio gives you. At 405 sq ft with an actual separated bedroom, it’s the smallest model in the lineup with a real bedroom instead of an open studio layout, which official guidance describes as fitting anyone who wants a real bedroom on a small lot.
For a home office, that separated bedroom becomes a genuine second room: a quiet space to close the door during calls, or a spot to set up a daybed so the office can convert into a guest room when family visits. At $237,000 and a 5 month build, it costs more than the Four Fifty but buys you a structure that isn’t locked into being an office forever. If there’s any chance you’ll want this space to become a rental or an in-law suite down the road, the 405 keeps that door open without jumping all the way up to a two-bedroom model.
If you need more room: Five Five Five
The Five Five Five is worth a look if “home office” really means “home office plus meeting space.” At 555 sq ft with one bedroom and one bath, it’s built for couples and long-term tenants, but the extra 150 sq ft over the 405 is enough to carve out a small conference corner, a second workstation, or a proper waiting area if clients or contractors visit in person. At $267,000 and a 5 month timeline, it’s the largest of the three models here, and still well under half the price of the largest homes in the Framework First lineup.
Pricing, financing, and next steps
All three of these prices are complete, covering a permitting budget, plans, foundation, the factory build, delivery, utility hookups, appliances, and final inspection. Exact permit costs are set by your city and county and confirmed during your feasibility study, and any property-specific site work like septic upgrades or retaining walls isn’t part of the listed price, though we handle that in-house as part of your contract too. Before you commit to a model, run your numbers through the ADU cost calculator to see how the price breaks down for your specific lot, and check pricing for the full 14-model lineup if you want to compare beyond these three.
If you’re not sure your lot can support a backyard build, or you’re on an empty lot with no existing structures, a feasibility study is the right first step before you lock in a model.
Frequently asked questions
What’s the cheapest ADU model for a home office?
The Four Fifty is the least expensive option at $180,000, with a permitting budget included, for 450 sq ft. It’s a studio with one bathroom, built specifically for a private studio for one, which is the same footprint most solo home offices need.
Do I need a bedroom in my office ADU?
Not necessarily. If the space is purely a work office, the Four Fifty’s studio layout skips the bedroom entirely and keeps the price down. If you want the option to use the space as a guest room or future rental, the 405’s separated bedroom layout gives you that flexibility for $237,000.
How fast can a home office ADU be built?
The Four Fifty has the fastest timeline in the entire lineup at 4 months. The 405 and Five Five Five both run about 5 months. All three are built roughly 97% in the Salinas, CA factory, then crane-delivered to the property in a single day, which is what keeps the on-site timeline short.
Is a bigger model ever worth it for an office?
It depends on how you’ll use the space. If you’re strictly working solo, extra square footage in a larger model mostly goes unused. But if you regularly host clients, need a meeting area, or want a second workstation, the Five Five Five’s 555 sq ft gives you that room without pushing into two-bedroom, family-sized territory.
Can an office ADU convert to a rental later?
Yes, and this is a real reason to consider the 405 over the Four Fifty. A studio can work as a rental, but a model with a separated bedroom, like the 405, tends to read as more livable to a future tenant or in-law, which is exactly what its official use case describes: anyone who wants a real bedroom on a small lot.
Not sure which size fits your lot and budget? Start a feasibility study or browse the full model lineup to compare every option side by side.