Can I build a backyard home in Lake Forest Park?
Since 2023, Washington law lets most city lots hold up to two more homes. Lake Forest Park 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 Lake Forest Park allows.
The headline standards. Tap any one for the full wording and the code section.
ADUs per lot2Full wording
2 — 'Up to two accessory dwelling units may be permitted on a lot with a single-family dwelling.' None if the lot has two middle-housing units such as a duplex (LFPMC 18.50.050(A), Ord. 25-1310)
Max size1,000 sq ftFull wording
1,000 sq ft — the ADU must be subordinate 'with a floor area that does not exceed 1,000 square feet' (LFPMC 18.50.050(C)); the old 'or the floor area of the principal residence, whichever is less' was deleted. An accessory building may not exceed 1,500 sq ft of floor area including garage space (LFPMC 18.50.060(B))
Max height25 ftFull wording
25 ft — accessory buildings 'which include an accessory dwelling unit ... can be up to 25 feet in height', if the building meets the zoning rules for the main building (LFPMC 18.50.060(F)); zone limit 30 ft (LFPMC 18.22.070)
Front setback20 ft in R-7.2Full wording
20 ft in R-7.2 (LFPMC 18.22.060(A)); also 20 ft in R-9.6, R-10 and R-15. ADUs must meet the zone's setbacks (LFPMC 18.50.050(B))
Side setback5 ft minimum each side, 15 ft combined in R-7.2Full wording
5 ft minimum each side, 15 ft combined in R-7.2 (LFPMC 18.22.060(B)); same in R-9.6, R-10 and R-15. ADUs must meet the zone's setbacks (LFPMC 18.50.050(B))
Rear setback15 ftFull wording
15 ft — 'Accessory dwelling units shall be placed no closer than 15 feet to the rear property line unless abutting a public alley not routinely snow plowed, then the accessory dwelling unit may be placed along the lot line' (LFPMC 18.50.060(E)); R-7.2 zone rear yard 15 ft (18.22.060(C)); accessory buildings at least 10 ft from the main building (18.50.060(D)) In RS-15 the zone rear yard is 20 ft (LFPMC 18.18.060(C)) and an ADU meets zone setbacks.
Lot coverage35% of net lot area for all buildings in R-7.2Full wording
35% of net lot area for all buildings in R-7.2 (LFPMC 18.22.050); impervious surface 45% (18.22.080). R-9.6 and R-10 30%, R-15 27.5%. Accessory buildings combined: 10% of the lot, up to 1,500 sq ft when one contains a DADU (LFPMC 18.50.060(A))
Parking1 space per ADUFull wording
1 space per ADU, in addition to the house's parking, unless the ADU is within one-half mile of a major transit stop (LFPMC 18.50.050(G), Ord. 25-1310). A converted garage's lost spaces must be replaced on site (18.50.050(F)(1))
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 units, as defined by this title, are permitted provided they meet the following development criteria' (LFPMC 18.50.050, Ord. 25-1310); ADUs are a permitted use in R-20, R-15, R-10, R-9.6, R-7.2 and SG-LDR (e.g. LFPMC 18.22.010(F), 18.45.010(E)). The old rule that ADUs on lots under 10,000 sq ft must be attached was deleted. Not allowed on a lot without public sewer (18.50.050(E))
Minimum lot size
None for an ADU — the 7,200 sq ft minimum was deleted and 'Accessory dwelling units are permitted on existing lots substandard in minimum lot area' (LFPMC 18.50.050(D)); zone minimums for new lots: R-7.2 7,200 sq ft, R-9.6 9,600 sq ft, R-10 10,000 sq ft (LFPMC 18.22.030, 18.21.030, 18.20.030)
Do you have to live there?
No — Ord. 25-1310 deleted 'Either the primary residence or the accessory dwelling unit must be owner-occupied' from LFPMC 18.50.050
Can it be sold on its own?
Yes — 'An ADU may be sold as a condominium unit or as a separate piece of property through the unit lot subdivision process.' (LFPMC 18.50.050(H), Ord. 25-1310)
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
Plans Lake Forest Park has already approved.
A pre-approved plan skips the design review: Lake Forest Park 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 Lake Forest Park 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 Lake Forest Park 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.
6 sources, read November 5, 2026
- www.cityoflfp.gov/DocumentCenter/View/12490 (Ord. 25-1310 as adopted, with Exhibit A redline of LFPMC 18.08, 18.16–18.22, 18.45, 18.50.050, 18.50.060, 18.58.030)
- cityoflfp.gov/695/Middle-Housing-Development-Regulation-Am
- www.cityoflfp.gov/165/Permit-Center
- www.cityoflfp.gov/610/Interactive-Maps
- codified LFPMC at https://ecode360.com/LA4507 (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 Lake Forest Park allows, what could fit, and a planning cost range. Free, no obligation.