Free Mercer Island homeowner guides

Plan your Mercer Island project with fewer surprises.

Mercer Island rules for house size and placement, including special limits for sloped properties.

Best first read

Begin with the parcel's zoning and base dimensions.

Compare Mercer Island R-8.4, R-9.6, R-12, and R-15 lot dimensions, setbacks, height, gross floor area, lot coverage, and hardscape rules.

Mercer Island zoning and setbacksCompare the base rules and official sources →

Property & site

See what may fit on the lot and what property issues need a closer look.

Mercer Island ADU and DADU rulesMercer Island ADU and DADU guide

See Mercer Island ADU and DADU rules for two units, 1,000-square-foot size, slope-based coverage, setbacks, trees, Type II review, utilities, and permits.

Read ADU guide →Mercer Island tree rulesMercer Island tree permits, retention, and replacement rules

Understand Mercer Island tree-permit thresholds, exceptional and critical-area trees, 30 percent development retention, replacement ratios, pruning, and hazard removal.

Read guide →Mercer Island zoning and setbacksMercer Island residential zoning and setbacks by zone

Compare Mercer Island R-8.4, R-9.6, R-12, and R-15 lot dimensions, setbacks, height, gross floor area, lot coverage, and hardscape rules.

Read guide →

Permit process

Understand what to prepare, what the city reviews, and who responds to corrections.

Mercer Island permit typesThe different types of permits in Mercer Island

Understand the main Mercer Island permit families, when several approvals may be needed, and where to find the official requirements.

Compare permit types →

Costs & timing

Use city targets and real permit data to plan a more realistic schedule and budget.

Mercer Island permit timelinesHow long permits take in Mercer Island

Use Mercer Island's published targets or observed results where available, with clear notes about what the numbers include.

See timing guide →

Useful across the Eastside

Guides for decisions every homeowner faces.

These explain common terms and choices. Your city's rules still control what is allowed on the property.

When do you need an architect?Compare Eastside requirements and learn when an engineer or architect is the right call.Where to find house plans by jurisdictionFind approved floor plans, permit drawings, and site records in Seattle, Eastside cities, and unincorporated King County.Before hiring a custom-home architect: what homeowners should prepareCreate an architect interview packet with a property screen, ownership-horizon strategy, homeowner brief, budget, title and HOA records, and a clear responsibility matrix.Structural choices that matter in a custom homeThe structural decisions worth resolving early in a custom-home design, before they turn into redesign, permit revisions, and expensive field changes.FAR, lot coverage, and impervious surfaceUnderstand the capacity and site terms in a preliminary property feasibility study, with simple examples.