Everything homeowners ask about building an ADU in Redmond — answered with 2026 data.
Yes, ADUs are allowed in Permitted (P) in the Neighborhood Residential (NR), Neighborhood Multifamily (NMF), Neighborhood Mixed-Use (NMU), Citywide Mixed-Use (CMU), Marymoor Village Edge (MME), Downtown Edge (DTE), Downtown Core (DTC), Town Center (TWNC), Urban Recreation (UR) and RA-5 zones (Redmond Zoning Code 21.04.0100, Residential Use Table, Ord. 3186; Ord. 3220). Standards are at RZC 21.04.1110, Accessory Dwelling Units and Tiny Homes. For most homeowners the zone is NR, the Neighborhood Residential zone created by Ordinance 3186 in place of the old R-4/R-5/R-6 single-family zones. RCW 36.70A.681(1)(c) independently requires two ADUs in every zoning district inside an urban growth area that allows single-family homes — except on lots designated with critical areas or their buffers, which RCW 36.70A.681(4) exempts entirely. Confirm your parcel's zone with Redmond's Planner on Call at 425-556-2494 or planneroncall@redmond.gov in Redmond, WA. The maximum size for a detached ADU is 1,000 sq ft. "The total square footage of an ADU shall not exceed 1,000 square feet" (Redmond Zoning Code 21.04.1110.C.3.a), which is exactly the floor RCW 36.70A.681(1)(f) sets — a city may not cap an ADU below 1,000 sq ft, and Redmond has not gone above it. Two discretionary escapes exist: if the ADU occupies an entire single floor of the primary dwelling the Administrator may allow more square footage to use the floor area efficiently, and on a site larger than 10,000 sq ft the Administrator may allow more if the ADU is an affordable housing unit or a public benefit is provided (RZC 21.04.1110.C.3.b-c). Watch the separate accessory-structure cap: the footprint of accessory structures may not exceed 60 percent of the footprint of the ground-floor living area (excluding garage) of the primary dwelling, and in no case may the ADU portion of an accessory structure exceed 1,000 sq ft (RZC 21.04.1120.C.2). On a small house that 60 percent rule bites before the 1,000 sq ft does — if it would push your ADU below 1,000 sq ft, raise RCW 36.70A.681(1)(f) with the planner. Attached ADUs can be up to Same 1,000 sq ft cap. Redmond has an ADU-friendliness score of 9/10. Check our full Redmond ADU rules page for complete zoning details.
ADU construction in Redmond typically costs $255,000-$460,000. The cost per square foot averages $310-$510. Garage conversions are more affordable at $125,000-$255,000, while prefab ADUs cost $185,000-$355,000. Permit fees add Confirm current building permit and plan review amounts with Redmond Development Services at 425-556-2494 — the fee schedule is not part of the zoning code and the city's fee page could not be retrieved for this entry to your budget. See our detailed Redmond ADU cost guide.
Detached ADUs in Redmond can be up to 1,000 sq ft. "The total square footage of an ADU shall not exceed 1,000 square feet". Attached ADUs are limited to Same 1,000 sq ft cap. Junior ADUs (JADUs) have a cap of Not a category in Washington — Redmond's code has no junior ADU designation. What it does have instead is the tiny home: a tiny home counts against the two-unit allowance and may not exceed 400 sq ft (Redmond Zoning Code 21.04.1110.C.1 and C.3.d). Maximum height is The height limit of the underlying zone — 38 feet in the Neighborhood Residential zone (Redmond Zoning Code Table 21.08.200.B, Base Maximum Height). Accessory structures are normally capped at 22 feet, but RZC 21.04.1120.C.1 carves out "accessory structures that contain accessory dwelling units, which shall not exceed the height maximum of the underlying zone." State law separately bars any roof height limit on an ADU below 24 feet unless the principal unit's own limit is lower (RCW 36.70A.681(1)(g)). Note that Redmond's older Accessory Structure handout (DR-014) has circulated with a 28-foot ADU figure that predates Ordinance 3220 — confirm with Planner on Call at 425-556-2494. You are allowed up to 2 ADUs per residential lot. "Two ADUs or tiny homes shall be allowed on each residential lot" on a qualifying lot.
Rear setback: 5 feet in the Neighborhood Residential zone — the same rear setback as the house (Redmond Zoning Code Table 21.08.300.A). Accessory structures in NR and NMU "shall comply with the underlying setback regulations of the zone" (RZC 21.04.1120.C.5), so a detached ADU takes the same 5 feet; in the Neighborhood Multifamily zone the accessory-structure side interior and rear setbacks are 5 feet. The alley setback is 2 feet, and RZC 21.04.1110.C.2.b goes further: "Detached ADUs may be sited immediately abutting a lot line if the lot line abuts a public alley or right-of-way, overriding other setback regulations." That is broader than the state minimum, which covers only alleys (RCW 36.70A.681(1)(i)). Side setback: 3 feet side interior and 10 feet side street in the Neighborhood Residential zone, the same as for the house (Redmond Zoning Code Table 21.08.300.A; RZC 21.04.1120.C.5). Both may vary for developments complying with the zero lot line regulations at RZC 21.16.200.D. State law bars setbacks for ADUs more restrictive than those for principal units (RCW 36.70A.681(1)(h)). Front setback: 10 feet in the Neighborhood Residential zone (Redmond Zoning Code Table 21.08.300.A). Accessory structures are prohibited within the front yard setback altogether, with a narrow exception for garages where lot width at the front street is under 50 feet, steep grades are present, or compliance would endanger pedestrian and vehicular safety (RZC 21.04.1120.C.4). RZC 21.08.300.A.2 adds that no structures, accessory structures included, are permitted in setback areas at all — only improvements under 30 inches above grade, fences, landscaping and similar. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None — anywhere in Redmond. Table 21.40.010.D, Required Off-Street Parking, gives the accessory dwelling unit and the tiny home a ratio of "Dwelling unit (0, –)" in all three location columns: within a quarter mile of frequent transit or in a TOD focus area, in a Center but not within a quarter mile of frequent transit, and All Other Locations. By comparison a detached principal dwelling still needs 1.0 space in All Other Locations. Redmond has gone past what state law demands: RCW 36.70A.681(2)(a) only forbids requiring parking within a half mile walking distance of a major transit stop, and caps what a city may require elsewhere at one space per unit on lots under 6,000 sq ft and two per unit on larger lots. The old rule at RZC 21.08.220.C.6, one off-street space per ADU, was repealed with the rest of that section. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. RZC 21.04.1110 contains no owner-occupancy provision, no prohibition on renting the owner's unit and no recorded-instrument requirement — all of which the repealed RZC 21.08.220.C.5 used to impose ("Either the primary dwelling unit or the ADU must be occupied by an owner of the property. The owner-occupied unit shall not be rented to others."). Redmond could not reinstate it if it wanted to: RCW 36.70A.681(1)(b) bars a city from requiring the owner of a lot with an ADU to reside in or occupy the ADU or another housing unit on the same lot. The old ban on subdividing or segregating an ADU in ownership (former RZC 21.08.220.C.4) is likewise gone. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Redmond is typically Confirm with Redmond Development Services at 425-556-2494 — no ADU-specific review timeline is published in the zoning code, and the city's own permit pages could not be retrieved for this entry (www.redmond.gov blocks automated access). Redmond adopted Ordinance 3174 in 2024 to conform its permit review procedures to Washington's SB 5290 permit-timeline law, so statutory review clocks apply; ask which category your application falls into. Plan check: Standard building plan review; no ADU-specific plan check process appears in the zoning code. Where an ADU is created inside an existing structure, expect the Building Official to look at the ceiling-height waiver at RZC 21.04.1110.C.6. Note that Redmond's code does not itself carry the state's conversion protection — RCW 36.70A.681(1)(j) requires a city to allow ADUs converted from existing structures, detached garages included, even where they violate current code requirements for setbacks or lot coverage, while RZC 21.04.1110.C.2.b still says detached ADUs "must each conform to all lot coverage restrictions." If you are converting a garage that does not meet today's setbacks, cite the statute. Pre-approved plans availability: None found in a City of Redmond source as of September 1, 2026. Neighbouring Kirkland runs a pre-approved detached ADU plan gallery; no equivalent Redmond programme appears in the zoning code, and the city's own pages could not be retrieved for this entry. Confirm with Planner on Call at 425-556-2494 before assuming you must pay for a full custom set.
Average ADU rental income in Redmond: 1-bedroom units rent for $2,050-$2,700/month, 2-bedroom units for $2,600-$3,400/month. Short-term rentals: Confirm with the City of Redmond before you list. Redmond's zoning code treats bed and breakfast inns and boarding houses as a separate, limited use in the neighborhood zones (RZC 21.04.0100, note 2: no more than eight rental rooms), but no short-term rental chapter of the Redmond Municipal Code could be retrieved for this entry — www.redmond.gov and the hosted municipal code both block automated access. A city business licence is the usual starting point. Long-term letting of an ADU is unrestricted: the owner-occupancy and rental limits in the repealed RZC 21.08.220 are gone. Expected ROI: 5-7% annual return.
The minimum lot size for an ADU in Redmond is No ADU-specific minimum. State law requires a city to allow an ADU on any lot that meets the minimum lot size for the principal unit (RCW 36.70A.681(1)(e)), and RZC 21.04.1110 imposes none. The Neighborhood Residential zone's own lot standards run to a 3,000 sq ft average minimum lot size, 20-foot minimum lot width and frontage, and a 30-foot minimum lot width circle (Redmond Zoning Code 21.08.143.B.2 as adopted by Ord. 3186, renumbered to RZC 21.08.200 by Ord. 3220). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Redmond, a garage conversion typically costs $125,000-$255,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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