Redmond ADU Cost: What Homeowners Should Budget For
A detached ADU on a typical 5,000–7,000 sqft Redmond lot generally plans in the high-$200k to high-$300k all-in range, with design, permits, and utility connection charges tracked separately. Redmond Planning & Community Development runs ADU permits through the city's PRO online portal, with standards set in RZC 21.08.220. Site condition and utility scope are the largest cost variables on Redmond lots; city fees are real but smaller than construction. Confirm current fees against Redmond's published schedule 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 Redmond permit and utility fees against the official sources linked below before committing a budget.
Redmond ADU cost tracks closely to Bellevue and Kirkland on construction and is most sensitive to utility and site-prep scope. The PRO portal and RZC 21.08.220 are the cleanest starting points for what the city actually requires.
Redmond cost drivers
Construction dominates Redmond ADU cost — typically 75–85% of all-in spend on a 5–7k lot. Redmond's mix of newer housing stock makes structural-surprise risk on conversions a little lower than older markets, but utility scope can still be material.
RZC 21.08.220 sets the ADU dimensional rules that govern feasibility. Design cost tracks the code's current standards — confirm the version at feasibility so design hours don't get spent against an outdated rule set.
Permits are filed through Redmond's PRO portal. Like Bellevue and Kirkland, online submittal is the only channel; permit and review fees are published on the city's Building Permits page.
Utility connections in Redmond — including water/sewer General Facility Charges (GFCs) — are billed by Public Works separately from building permits. The GFC line can be material; confirm the current rate before committing a budget.
Tree retention and stormwater requirements scale with site sensitivity. A pre-design site walk is the cheapest correction on Redmond lots with mature trees or critical-areas exposure.
What Redmond actually charges — and how to verify it
Redmond Planning & Community Development is the issuing department for ADU permits. Permit and plan-review fees are published on the city's Building Permits page.
ADU code lives in RZC 21.08.220 (Accessory Dwelling Units). The code defines size, parking, and owner-occupancy rules that govern feasibility and design.
Submittals run through Redmond's PRO (Permit & Resource Online) portal — the official channel for ADU permit filing and fee payment.
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
Site condition is the largest cost variable on Redmond lots — slope, drainage, mature trees, and existing utility capacity drive more dollars than finish level.
Water and sewer GFCs are billed by Redmond Public Works. They are real, scale with the new demand, and are separate from the building permit. Confirm the current rate on your specific parcel.
Stormwater requirements scale with added impervious surface. Drainage solutions designed in early are cheaper than drainage solutions designed at correction.
Electrical service capacity is the same conversation as elsewhere on the Eastside — 200A upgrades and feeder runs are common on older Redmond homes.
Picking the cost-efficient project type
Garage conversions in Redmond can be the cost-efficient path when the existing structure is permitted and structurally sound. New detached ADUs price competitively where RZC 21.08.220 dimensional rules and the lot's buildable envelope allow standard construction. Choose between paths at feasibility, not after design starts.
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.
Redmond ADU pricing questions
What does a typical detached ADU cost in Redmond?
On a 5,000–7,000 sqft lot in Redmond, 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 Redmond?
Often yes. An attached ADU (AADU) on a typical 5–7k Redmond 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 Redmond 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 Redmond?
Redmond 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
Where do I file a Redmond ADU permit?
Through Redmond's PRO (Permit & Resource Online) portal — the city's official online submittal channel for ADU permits.
Which Redmond code section governs ADUs?
RZC 21.08.220 — Accessory Dwelling Units. The section sets size, parking, and owner-occupancy rules that govern feasibility. Confirm the current version at feasibility.
Do Redmond utility connection fees apply to every ADU?
Water/sewer General Facility Charges (GFCs) typically apply when new demand is added. They are billed by Redmond Public Works separately from the building permit — confirm current rates on your specific parcel.
What should Redmond homeowners verify before budgeting for an ADU?
Current Planning & Community Development permit fees, current Public Works GFCs, the current version of RZC 21.08.220, and whether the lot triggers critical-areas or tree-retention review. A feasibility walk covers all four.
Are Redmond permit fees the final project cost?
No. Permit fees are one line item. Construction, design, utility GFCs, and site prep are separate and typically much larger. The cost table on this page tracks each line independently.
Redmond cost & permit sources we used
Every claim on this page about Redmond 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 Redmond — Planning & Community Development · city pageResidential Permits — City of Redmond
Lists residential permit types Redmond requires for ADU/DADU projects.
Accessed 2026-06-03
- Redmond Zoning Code · codeRZC 21.08.220 Accessory Dwelling Units
Redmond Zoning Code section governing ADU dimensional standards, parking, and owner-occupancy — affects design and feasibility cost.
Accessed 2026-06-03
- City of Redmond · help articlePermit & Resource Online (PRO) Portal
Redmond's PRO online portal — the official submittal channel for ADU permits and fee payment.
Accessed 2026-06-03
- City of Redmond — Planning & Community Development · fee scheduleRedmond Building Permit Fees
Authoritative source for current Redmond building permit, plan review, and impact fees.
Accessed 2026-06-03
- City of Redmond — Public Works · utilityRedmond Utilities — Water & Sewer
Water/sewer connection charges and General Facility Charges (GFCs) for new ADUs in Redmond are billed by Public Works separately from building permits.
Accessed 2026-06-03