Costco Prefab ADU: What You Can Actually Buy, Permit, and Live In

By The Dwelling Index Editorial Team · Last updated June 1, 2026 · Last verified: June 1, 2026

The Dwelling Index is an independent research resource covering ADU financing, costs, and regulations. We are not a lender, broker, or builder.

The Costco prefab reality, in one table

The word “Costco” tells you where you’re shopping, not what you’re legally allowed to live in. The product category — storage shed, finished studio, or true ADU — decides the outcome. We classified the current Costco-related options below. Prices and availability rotate, so treat these as a map, not a quote.

Inclusions vary by configuration and quote. Across every option, the buyer is responsible for permits, local code compliance, and HOA approval; foundation, site work, and utility connections are confirmed on your current quote, not assumed. Sources: Costco.com product pages; Studio Home (studio-home.com), captured June 2026.

Is there really a “Costco prefab ADU”?

Not as a single product. Costco is a retail gateway, not a homebuilder or a permitting authority. What people call a “Costco prefab ADU” is almost always one of three different things: an ordinary storage shed, a finished backyard studio offered through Costco Next (the Studio Shed Signature or Portland series), or — confusingly — the full kitchen-and-bath ADU lines from the same manufacturer, sold under the Studio Home name on the company’s own site and not currently surfaced on Costco Next.

What “Costco Next” actually is

Costco Next is a members-only program that gives you exclusive pricing from vetted partner brands — but instead of buying through a Costco warehouse, Costco refers you to the partner’s own website, where you purchase directly. The partner handles fulfillment, customer service, and returns. For our topic, the partner is Studio Shed. So when you “buy a Studio Shed from Costco,” you’re really getting Costco member pricing on a Studio Shed order placed on Studio Shed’s own website (Costco Next; SlashGear, May 2026).

Studio Shed and “Studio Home” are the same company

Studio Shed and Studio Home are the same Colorado manufacturer — a panelized-prefab company with roughly 18 years in business and 6,000+ projects; both storefronts cross-reference each other and the company appears to be migrating toward the “Studio Home” name. The distinction that matters:

• The Costco Next channel surfaces the studio tier — finished backyard rooms with electrical, not kitchen-and-bath dwellings.
• The company’s full ADU lineup — Summit, Aspect, and Carriage House — sells directly on studio-home.com, not through Costco Next, and starts far higher.

The one question that decides everything

Is the structure legally habitable where you live? A shed that’s insulated, attractive, and even professionally installed is still a shed until it meets residential code and earns a permit and a certificate of occupancy (the document a city issues confirming a space is legal to occupy).

Can you legally live in a Costco shed or Studio Shed?

Generally, no — not as sold, and not automatically. To be a legal dwelling, a structure must meet residential building code and, for an ADU, carry an ADU permit and a certificate of occupancy. A Costco studio or shed can become legally habitable, but only after you add everything the code requires — and get the city to sign off.

What separates a shed from a dwelling (code, in plain English)

• Permanent heating capable of maintaining about 68°F — you can’t rely on a space heater you carry in and out.
• A minimum ceiling height of about 7 feet in habitable rooms.
• Natural light and ventilation (minimum window sizes) or an approved mechanical equivalent.
• Emergency escape and rescue openings (egress windows) in sleeping rooms — a window large enough to climb out of in a fire.
• An ADU specifically needs its own kitchen and bathroom to meet the dwelling definition (LA County Planning). A bare studio shell delivers almost none of this out of the box.

The manufactured-vs-modular distinction

How a unit is built changes what it legally is. HUD-code manufactured homes are regulated under federal manufactured-housing construction and safety standards overseen by HUD. Modular and panelized units — Studio Shed/Studio Home fall here — are reviewed under state and local building codes; when configured and permitted as dwellings, they’re inspected much like site-built homes. A shed or studio product, by contrast, is typically classified as an accessory structure — not a dwelling — until the local building department says otherwise.

One state’s rule, decoded: California’s “66323 units”

Rules are local, but California shows how favorable a modern ADU statute can be. Under Gov. Code § 66323 — the “state-exempt” or “66323 unit” provision — a local agency must approve ministerially (no discretionary hearing) a detached ADU of up to 800 square feet, with 4-foot side and rear setbacks, at least a 16-foot height limit, within a 60-day clock. But “ministerial approval” doesn’t mean “automatic approval.” Your unit still has to qualify: correct size, correct setbacks, and a proper ADU permit with plans. A Costco shed doesn’t qualify on day one.

California also regulates short-term rentals for these units: “66323 units” may not be rented for terms shorter than 30 days (§ 66323(e)), so a new Airbnb is generally off the table. As of January 1, 2026, JADU owner-occupancy is triggered only when the JADU shares sanitation with the main house (AB 1154, § 66333). California updates its ADU laws nearly every January — confirm current statutes before relying on specifics. For a deep dive, see our California ADU laws guide.

What does the Costco / Studio Shed path actually cost?

The sticker is one major line item, not the whole project. A Costco/Studio Shed studio runs roughly $17,000 (DIY shell) to $73,000 (installed), and even the installed price covers finishes and electrical — never a kitchen, bathroom, plumbing, HVAC, permits, or utility connections. The company’s true kitchen-and-bath ADU lines start near $98,000 for the unit alone. Once you add everything a legal, rentable unit requires, a realistic all-in budget is about $60,000–$140,000+ for a converted shell or $130,000–$170,000+ for a purpose-built prefab ADU.

Costco-channel studio prices (Costco Next)

Live Costco Next prices sit behind a member sign-in and rotate; re-confirm against your current quote.

Sources: House Digest & Outdoor Guide (2024–2025) for installed Studio Shed tiers; Costco.com/Slickdeals listings (2022) and lifestyle coverage (2025) for the Medano DIY price. Studio Shed installed units also require electricity within ~150 feet and a level pad.

The company’s real ADU lines (bought direct, not via Costco)

Studio Home’s published starting prices fluctuate with promotions — confirm the live figure when you quote.

Source: studio-home.com (Summit Series, Aspect, Carriage House), captured June 2026. Starting figures are for the unit only and change with promotions. Foundation, site work, utility laterals, permits, and local energy compliance are excluded.

The Sticker → Legal-Occupancy Cost Stack

Here’s the part nobody assembles for you: the line items between the sticker and a unit you can legally occupy or rent. These are national/regional ranges, not quotes.

“Plan check” is the city’s engineering review of your drawings; “soft costs” are non-construction expenses like design, engineering, and permits.

How homeowners actually pay for a Costco-sourced ADU

Most people use one of four lanes, matched to their equity and how much of the work they’re financing. A DIY shell is often cash; a finished studio is commonly a HELOC (a revolving line secured by your home’s equity) or a home equity loan; a full legal ADU is usually a renovation loan or a construction loan that funds the build in stages. We present financing as paths, not lender rankings, and we never quote rates or payments as promises.

One nuance specific to prefab: how the unit is classified (modular/panelized vs. HUD-code manufactured) can change which loan products you qualify for and whether the unit appraises as part of the real property. Confirm classification before you choose a lane.

Is the Costco / Studio Shed deal worth it?

It’s worth it when the product matches your legal use — and a poor choice when you’re buying a non-habitable shed and assuming a cheap conversion later. For a home office, gym, art studio, or guest overflow without permanent sleeping use, a Costco/Studio Shed unit delivers real quality at a member discount. For a long-term rental, an aging-parent suite, or any use that requires a permitted dwelling, the studio is only the first major line item.

Sources: Costco/Studio Shed use-case positioning; LA County ADU definition; Cal. Gov. Code §§ 66323(e), 66333(g).

If your goal is a rentable or multigenerational unit, the most useful next step is to compare complete prefab ADUs that ship closer to turnkey — nationally shipping providers such as Modular Home Direct and compact foldable units like the BOXABL Casita for tight lots.

What to verify before you buy anything through Costco or Studio Home

Confirm five things in writing before any deposit: local ADU eligibility, the product’s code path, the complete scope, the utility plan, and who is responsible for permits and inspections. The most expensive ADU mistakes happen before the structure ships.

The 12 questions to ask before you buy a Costco-related ADU product:

1. Is this product designed and warrantied for legal residential occupancy — or is it a shed/studio?
2. What code is it built to — IRC modular/panelized, or HUD manufactured?
3. Does the price include stamped, permit-ready plans for my jurisdiction?
4. Does it include a kitchen?
5. Does it include a bathroom with code plumbing?
6. Who pulls the permits — me, or the company?
7. Who signs the permit application as the responsible party?
8. Is the foundation included, or priced separately?
9. Are water, sewer, and electrical hookups (utility laterals) included?
10. Are local energy-compliance calculations (e.g., Title 24 in California) included?
11. What happens — and what does it cost — if my city rejects the plans?
12. What, specifically, is excluded from the quoted price?

Get the answers in writing. A reputable prefab company will provide them without hesitation; vague answers are the red flag.

Costco vs. a prefab ADU company vs. modular vs. site-built vs. garage conversion

The Costco/Studio Shed route is best for a product-led starting point and finished studio space; a dedicated prefab ADU company offers a more complete dwelling scope; site-built and garage conversions often win for tight lots, custom layouts, or jurisdictions that complicate prefab approval.

Cost benchmarks: detached ADUs commonly run ~$150,000–$475,000 all-in in higher-cost metros (Neighbor; Clever Design); California garage conversions often $70,000–$250,000 depending on scope (Golden State ADUs; BFPM).

If a garage conversion is on the table, it’s frequently the cheapest route to a legal unit because the structure and some utilities already exist — worth pricing against any prefab before you commit. See our guides to prefab ADU cost, modular ADU companies, and manufactured home ADUs.

What if your city says no?

If your jurisdiction won’t approve the product as an ADU, don’t force the shed path — switch strategies. A “no” is almost always about the product category or the lot, not your goal, and there’s usually another route to the same outcome.

Methodology & sources

Frequently asked questions