Can I build a backyard home in Fircrest?
Since 2023, Washington law lets most city lots hold up to two more homes. Fircrest writes its own rules on top. Here’s what the code says, in plain English — and a free report on what may fit on your lot.
What Fircrest allows.
The headline standards. Tap any one for the full wording and the code section.
ADUs per lot2Full wording
2 — 'Up to two ADUs may be created per principal unit': one attached + one detached, two attached, or two detached in one or two structures (FMC 22.58.012(c)(3)). In R-4 and R-6, ADUs count toward the 2-units-per-lot unit density, so two ADUs with a house use it up (FMC 22.32.005 note 2)
Max size1,000 sq ftFull wording
1,000 sq ft — 'An ADU (either attached or detached) shall not exceed 1,000 square feet.' Garages built as part of a detached ADU do not count. The director may allow more for a whole floor of an existing multistory building if the footprint is not expanded (FMC 22.58.012(c)(6))
Max height24 ftFull wording
24 ft — 'The maximum height for a detached ADU is 24 feet' (FMC 22.58.012(c)(7)(A)); exceptions per FMC 22.58.007
Front setback25 ft in R-4 (same as the house)Full wording
Same as principal: 25 ft in R-4; 20 ft in R-6. An ADU 'shall meet the development standards, including setbacks ... applicable to the zone' (FMC 22.58.012(c)(7); 22.32.005; 22.36.005)
Side setback8 ft interior and 15 ft street side in R-4 (same as the house)Full wording
Same as principal: 8 ft interior and 15 ft street side in R-4; 5 ft for the first story and 8 ft for the second story in R-6 (FMC 22.32.005; 22.36.005; 22.58.012(c)(7))
Rear setback20 ft in R-4 and R-6 (same as the house)Full wording
Same as principal: 20 ft in R-4 and R-6 (FMC 22.32.005; 22.36.005). 'Detached ADUs may be sited at the lot line if the lot line abuts a public alley, unless the city or county routinely plows snow on the public alley' (FMC 22.58.012(c)(8))
Lot coverage40% for all structures combinedFull wording
40% for all structures combined; 50% impervious surface; floor area ratio 0.35 (R-4, FMC 22.32.005; R-6 has the same coverage limits, 22.36.005). ADUs must meet these limits (22.58.012(c)(7))
ParkingNoneFull wording
None — the parking table lists 'Accessory dwelling unit (ADU): None' (FMC 22.60.003). 'No additional off-street parking is required for an ADU unless the director determines that insufficient on-street parking will exist' (FMC 22.58.012(c)(11)). The city allows only one driveway (FMC 22.60.008, per the city ADU FAQ)
Where a city figure reads stricter than the state floor (RCW 36.70A.681), the floor may control — the report flags it for your parcel.
Living there, selling it, plans, time and fees.
Each answer is the code’s own wording, with the section it comes from. “Not published yet” means the city hasn’t posted a figure — the report asks the city, not the internet.
Are backyard homes allowed?
Yes — 'Accessory dwelling unit (subject to compliance with FMC § 22.58.012)' is an accessory use in R-4 and R-6 (FMC 22.32.003(a), 22.36.003). 'An ADU may be attached to, or detached from, the principal unit' (FMC 22.58.012(c)(2)). The director approves ADUs with administrative design review (22.58.012(b)) (Ord. 1740, June 16, 2025; Ord. 1754, Dec. 9, 2025)
Minimum lot size
None beyond the zone — 'ADUs are permitted on any lot that meets the minimum lot size required for the principal unit' (FMC 22.58.012(c)(13)). 8,000 sq ft in R-4 (FMC 22.32.005); 5,000 sq ft in R-6 (FMC 22.36.005)
Do you have to live there?
No — FMC 22.58.012 (as amended in 2025) has no owner-occupancy rule; subsections (c)(4) and (c)(10) are 'Reserved'
Can it be sold on its own?
Not addressed; RCW 36.70A.681 floor applies
Pre-approved plans
None found
How long the city takes
Not published
Impact fees
Not found; RCW 36.70A.681 caps ADU impact fees at 50% of the principal unit's. The 2026 Building/Planning Fee Schedule has no ADU impact-fee line
Plans Fircrest has already approved.
A pre-approved plan skips the design review: Fircrest has already checked the drawings, so the permit review is about your lot.
Loading the plans…
Pictures are the official pages’ own. A pre-approved plan is not a permit: the city still reviews your site.
The code is half the answer. Your parcel is the other half.
Lines and easements
Where the lot lines really are, which setbacks apply on each side, and whether a utility or access easement takes the corner you had in mind.
Critical areas and slope
Steep slopes, wetlands and streams come with buffers that no citywide number shows. The report reads the county’s maps for your parcel.
Sewer, septic, water, trees
Whether sewer reaches the lot or it’s on septic, where the water service is, and which trees a city protects — the things that decide where a unit can actually go.
What Fircrest allows, what could fit on your lot, and a planning cost range. If something won’t fit, the report says so — and shows what might.
Where this page comes from.
Read from the Fircrest municipal code and the city’s own pages on November 6, 2026. The same table feeds the HousUp report, so the report and this page never disagree. Cities amend their codes; before you design anything, confirm the current wording with the city.
7 sources, read November 6, 2026
- www.zoneomics.com/code/fircrest-WA/chapter_36 (FMC 22.58.012)
- www.zoneomics.com/code/fircrest-WA/chapter_21 (22.32)
- www.zoneomics.com/code/fircrest-WA/chapter_23 (22.36)
- www.zoneomics.com/code/fircrest-WA/chapter_37 (22.60.003)
- www.cityoffircrest.net/adu-information-faq
- ecode360.com/FI4443 (official code host, not readable by automated tools)
- RCW 36.70A.681 — the state floor for accessory dwelling units
Find out what your property could become.
Type your address. Within a few hours: what Fircrest allows, what could fit, and a planning cost range. Free, no obligation.