Can I build a backyard home in Bonney Lake?
Since 2023, Washington law lets most city lots hold up to two more homes. Bonney Lake 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 Bonney Lake allows.
The headline standards. Tap any one for the full wording and the code section.
ADUs per lot2Full wording
2 (BLMC 18.22.090(C)(1)(c)); 1 attached or detached on lots with undevelopable critical areas or in certain impaired reservoir watersheds (BLMC 18.22.090(C)(1)(a)-(b)).
Max size1,200 sq ft gross for a detached ADU, minimum 450 sq ftFull wording
1,200 sq ft gross for a detached ADU, minimum 450 sq ft (BLMC 18.22.090(C)(4)(b)); attached: 300–1,000 sq ft when the primary unit is up to 2,500 sq ft, 40% of the primary for 2,501–3,000 sq ft, 1,200 sq ft when the primary is over 3,000 sq ft (BLMC 18.22.090(C)(4)(a)).
Max height24 ft for any new detached ADUFull wording
24 ft for any new detached ADU; existing legal buildings over that height may be converted (BLMC 18.22.090(C)(10)(b)).
Front setback10 ft in R-1 (20 ft to a garage door)Full wording
Zone setbacks apply (BLMC 18.22.090(C)(10)); R-1: 10 ft for residences and accessory structures, 20 ft to a garage door (BLMC 18.14.060(C)).
Side setbackZone setbacks applyFull wording
Zone setbacks apply (BLMC 18.22.090(C)(10)); R-1: 5 ft (BLMC 18.14.060(D)).
Rear setbackNot confirmed yet — 20 ft or 10 ft in R-1; ask the cityFull wording
Not confirmed yet — ask the city. (R-1 rear is 20 ft for a residence and 10 ft for a separate garage or accessory building, BLMC 18.14.060(E); BLMC 18.22.090(C)(10) does not say which applies to a DADU). A DADU on a non-plowed public alley may reduce the alley setback to zero (BLMC 18.22.090(C)(10)(a)).
Lot coverage60% impervious surface in R-1Full wording
60% impervious surface in R-1 (BLMC 18.14.060(G)); no separate building-coverage limit.
Parking1 space for a 1-bedroom ADU, 2 spaces for 2+ bedroomsFull wording
1 space for a 1-bedroom ADU, 2 spaces for 2+ bedrooms; 1 space regardless of bedrooms on lots of 6,000 sq ft or less; in addition to the primary unit's spaces; tandem allowed on lots over 6,000 sq ft (BLMC 18.22.090(C)(9)).
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 — attached or detached ADU as an accessory use to a single-family dwelling, duplex, triplex or townhouse; not on lots with multifamily dwellings (BLMC 18.22.090(C)(1)-(2)). Zones are not listed in the section.
Minimum lot size
2,000 sq ft — the ADU must be on a legal building lot of at least that size (BLMC 18.22.090(C)(1)).
Do you have to live there?
No for most lots; required (owner in either unit at least 6 months a year) only on the critical-area and impaired-watershed lots limited to one ADU (BLMC 18.22.090(B)(2)).
Can it be sold on its own?
Yes — ownership may be separated by subdivision/segregation under ch. 58.17 RCW and BLMC Title 17, or by conversion to a condominium unit (BLMC 18.22.090(C)(5)).
Pre-approved plans
Not confirmed yet — ask the city.
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. BLMC 18.22.090(C)(3),(6) require a separate water meter and sewer or septic connection, with connection fees under BLMC 13.04.070 and 13.12.100.
Plans Bonney Lake has already approved.
A pre-approved plan skips the design review: Bonney Lake 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 Bonney Lake 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 Bonney Lake municipal code and the city’s own pages on November 5, 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.
2 sources, read November 5, 2026
Find out what your property could become.
Type your address. Within a few hours: what Bonney Lake allows, what could fit, and a planning cost range. Free, no obligation.