Bellevue ADU Cost: What Homeowners Should Budget For
A detached ADU on a typical 5,000–7,000 sqft Bellevue lot generally plans in the high-$200k to high-$300k all-in range, with design, permits, and utility connection charges tracked separately. Bellevue's published permit fees and Development Services review process are formal — applications run online through MyBuildingPermit.com. The largest single budget variable is finish level and site complexity (slope, trees, utility distance); permit fees are real but a smaller share than construction. Confirm current city numbers against Bellevue's Development Services published fees and your utility statement before committing a budget.
Last verified 2026-05-15
| Cost category | Under 3,000 sqft | 3,000–3,999 sqft | 4,000–4,999 sqft | 5,000–6,999 sqft | 7,000–9,999 sqft | 10,000+ sqft |
|---|---|---|---|---|---|---|
| All-in (DADU) | $136k–$195k | $168k–$239k | $199k–$284k | $261k–$369k | $293k–$414k | $325k–$458k |
| DADU construction | $120k–$160k | $150k–$200k | $180k–$240k | $240k–$320k | $270k–$360k | $300k–$400k |
| AADU conversion | $90k–$120k | $120k–$160k | $150k–$200k | $180k–$240k | $210k–$280k | $240k–$320k |
| Design & engineering | $9,000–$20,500 | $10,000–$23,000 | $11,000–$25,500 | $12,000–$28,000 | $13,000–$30,500 | $14,000–$33,000 |
| Permit & city fees | $6,800–$14,200 | $7,600–$16,400 | $8,400–$18,600 | $9,200–$20,800 | $10,000–$23,000 | $10,800–$25,200 |
Numbers above are planning estimates from current bids and recent Golden State ADU projects on Puget Sound lots — they are not city-published fees. Verify current Bellevue permit and utility fees against the official sources linked below before committing a budget.
Bellevue ADU cost is driven by construction and finish level first, site/utility second, and city fees third. Bellevue's pre-approved DADU plans can shorten review and trim design cost where they fit the lot.
Bellevue cost drivers
Construction dominates Bellevue ADU cost the same way it does in Seattle — typically 75–85% of all-in spend on a 5–7k lot. Finishes tend to spec higher in Bellevue, which is the single biggest reason Bellevue projects often land at the top of the construction range.
Lot constraints matter. Bellevue has more topography, tree-retention overlays, and shared driveways than typical Puget Sound suburbs. A buildable envelope analysis at feasibility is high-leverage.
Bellevue Development Services runs a formal permit-review track. Applications are filed through MyBuildingPermit.com. Each review cycle has a defined timeline, and corrections that aren't bundled cleanly extend total calendar time — which costs you in carrying costs more than in city fees.
Design and engineering scale with site, code, and overlay complexity. Bellevue's ADU Reform LUCA work changes the standards landscape — confirm the version of code your project will be reviewed under at feasibility.
Bellevue publishes a Pre-Approved Plans path for DADUs. Where the pre-approved plan fits the lot, design and review cost both drop. It does not fit every lot, but it's worth checking before drawing custom plans.
What Bellevue actually charges — and how to verify it
Bellevue Development Services is the issuing department. Permit, plan review, and impact fees are billed through MyBuildingPermit.com against the city's published fee schedule.
Bellevue is 100% paperless — every ADU permit application must be submitted online. Paper applications and plans are not accepted (sourced to Bellevue's Online Permitting Services page).
Utility connection and General Facility Charges are billed by Bellevue Utilities separately from building permits. Confirm current rates on your utility statement before budgeting.
Numbers in our cost table are planning estimates from Golden State ADU project data, not city-published fees. Always confirm current fees against the city's published schedule.
Site condition and utility scope
Topography is the biggest physical cost driver in Bellevue. Sloped lots and retaining-wall requirements add foundation cost and engineering scope; flat lots near the central corridors price closest to plan.
Tree retention shows up in design constraints and in construction-phase tree protection. A tree survey before drawing the building envelope prevents redesign.
Water and sewer connection charges in Bellevue are administered by Bellevue Utilities and can be material on lots where a new tap or upsize is required.
Electrical service capacity drives the same dollars in Bellevue as in Seattle — panel upgrades and feeder runs are common on older Bellevue homes.
Picking the cost-efficient project type
Garage conversions (AADUs) in Bellevue can be the cost-efficient path when the existing structure is sound and permitted. Where pre-approved DADU plans fit your lot, a new DADU can be competitive on cost-per-buildable-sqft because design and review fees shrink. Decide between paths at feasibility, not after drawings start.
What can increase the budget
Service-panel upgrades, new sewer side-line, water-meter sizing, and gas re-routing can each add thousands. The cost is real but the line item rarely appears in early estimates because it depends on field conditions and the utility provider's current schedule.
On garage conversions and additions, foundation upgrades, rotted framing, or missing seismic ties are the most common scope shocks. A pre-design structural walk catches these before they hit a change order.
Each round of permit corrections costs designer hours and calendar weeks. Resubmittals that bounce back at intake compound fast. A pre-screened submittal package is the highest-leverage place to defend the budget.
Cabinetry, tile, lighting, and appliances are where allowance budgets quietly drift 20–40% above plan. Locking spec early — not later — is the cheapest control.
Tight alleys, mature trees in the build envelope, slope, or shared driveways add labor hours, crane time, and material handling. They are city-agnostic but show up most on Puget Sound urban lots.
What reduces budget risk
An hour walking the lot with someone who has built ADUs in your city is worth ten hours of revised drawings. It catches setback, height, FAR, parking, and tree-protection constraints before they force redesign.
A side-sewer call, panel-capacity check, and meter-sizing question to the utility before drawings start prevents the most expensive late-stage surprises.
Pricing finishes to the level you actually want — not the level the spreadsheet rounds to — keeps change orders predictable.
A complete, code-cross-referenced submittal package shortens review and reduces corrections. Most permit overruns are correction-driven, not city-fee-driven.
A 10–15% contingency is the difference between an unexpected condition becoming a story and becoming a stalled project. Plan for it explicitly — don't borrow it from finishes.
No promised ROI, no guaranteed rent figures. Financing assumptions should be confirmed with a lender; rental assumptions should be confirmed against current local market data.
Bellevue ADU pricing questions
What does a typical detached ADU cost in Bellevue?
On a 5,000–7,000 sqft lot in Bellevue, WA, an all-in detached ADU generally plans at $261k–$369k including design, permits, site work, and construction. Larger or constrained lots shift the number up. These are planning estimates from current bids and recent projects — verify current city fees against the city's published schedule before committing a budget.
Are attached ADUs cheaper than detached ones in Bellevue?
Often yes. An attached ADU (AADU) on a typical 5–7k Bellevue lot plans at $180k–$240k for construction, vs $240k–$320k for new detached construction. Attached projects share foundation, roof, and one utility tap with the primary house — that's where the savings come from. The trade is that conversions hide more risk in existing conditions.
Go deeper: Read the Puget Sound ADU timeline guide: kickoff to keys guide
What's included in the Bellevue construction line?
$240k–$320k for a typical 5–7k lot. That covers foundation through final finishes — framing, MEP rough-in and trim, insulation, drywall, cabinetry, fixtures, flooring, exterior siding, and roofing. Site work, design, and permits are tracked as separate lines above. Numbers are planning estimates, not city-published fees.
How much do design and permits add in Bellevue?
Bellevue design typically plans at $12,000–$28,000, with permit and review fees of $9,200–$20,800 on a 5–7k lot. Both scale with project size and review complexity. City-fee ranges shown here are planning estimates — confirm current numbers against the city's fee schedule linked below.
Go deeper: Read the Seattle Design Review for ADUs: when it applies (2026) guide
Are Bellevue permit fees the same as total project cost?
No. Bellevue Development Services permit and plan-review fees are one line item. Construction, design, utility connection charges, and any impact fees are separate. The cost table on this page tracks each line independently for that reason.
Does Bellevue's pre-approved DADU plan path lower cost?
Yes — where the plan fits the lot. Pre-approved plans cut design hours and shorten review, which trims both the design and permit lines. Confirm fit at feasibility before assuming it applies to your parcel.
Can a Bellevue ADU project be submitted on paper?
No. Bellevue Development Services is 100% paperless; all ADU applications go through MyBuildingPermit.com (sourced to the city's Online Permitting Services page).
How much do utility connections add in Bellevue?
It depends on whether a new tap or upsize is required and on current Bellevue Utilities rates. Confirm the number on your specific parcel — utility connection fees are billed separately from building permits.
Go deeper: Read the Eastside deck cost & permits: cedar, IPE, composite (2026) guide
What should I verify before budgeting an ADU in Bellevue?
Lot constraints (slope, trees, easements), current Bellevue Development Services fees, current Bellevue Utilities connection charges, and whether the pre-approved DADU path applies. A feasibility walk covers all four in one visit.
Bellevue cost & permit sources we used
Every claim on this page about Bellevue permit fees, ADU code, submittal portals, or utility billing traces to an official city or zoning-code source. Construction numbers in the cost table come from current Golden State ADU project data and are presented as planning estimates — not city-published fees.
- City of Bellevue — Development Services · city pageMiscellaneous Land Use Permits (ADU)
Lists the ADU/DADU permit types Bellevue requires and where they sit in the cost stack.
Accessed 2026-06-03
- City of Bellevue · city pageADU Reform LUCA
Bellevue's published ADU code reform context affecting current ADU/DADU standards and review tracks.
Accessed 2026-06-03
- City of Bellevue · city pageOnline Permitting Services
Bellevue is 100% paperless — every ADU permit application must be submitted online through MyBuildingPermit.com.
Accessed 2026-06-03
- MyBuildingPermit (eGov Alliance) · fee scheduleMyBuildingPermit — Bellevue Fees
Published Bellevue jurisdiction page for fees, submittal requirements, and inspection scheduling.
Accessed 2026-06-03
- City of Bellevue · city pagePre-Approved Plans (DADU)
Bellevue pre-approved DADU plans path can lower design and review fees vs a fully custom DADU.
Accessed 2026-06-03
- Bellevue Utilities · utilityUtilities — Water / Sewer Connection
Water and sewer connection fees for new ADUs in Bellevue are administered by Bellevue Utilities and billed separately from building permits.
Accessed 2026-06-03