Additions and ADUs — more house, or a second one in the back yard

Start with what the lot allows

Every addition and ADU project begins the same way: we look up your zoning, your lot coverage, your setbacks, your height limit, tree retention and any critical-area overlays, and we tell you what is genuinely buildable. That first conversation saves people months. There is no point drawing a beautiful 900-square-foot cottage for a lot that will only carry 600.

Washington's ADU legislation has pushed cities across the state to allow accessory dwelling units far more broadly than they used to — but the specifics still differ from Kirkland to Bellevue to unincorporated King County: maximum size, maximum height, setbacks, parking, entrance location and design standards. We check your jurisdiction, not a general rule of thumb.

Room and second-story additions

Adding to a house is harder than building new, because everything has to marry into what is already there — the roof line, the floor heights, the siding, the foundation and the existing structure that now has to carry more. A good addition should be invisible from the street: same pitch, same materials, same window proportions. When you can tell where the old house ends, someone cut a corner.

Detached ADUs (DADUs)

A backyard cottage is the closest thing to a small custom home: its own foundation, its own utility connections, its own kitchen and bathroom, its own energy-code compliance. Done well it becomes long-term rental income, a place for parents, a place for adult children, or the flexible space that lets you stay in a house you have outgrown. Done cheaply it becomes a permit problem and a maintenance headache.

Garage and basement conversions

• Garage conversion (AADU) — often the fastest route to a legal second unit, but it needs insulation, a real floor assembly, egress, ventilation and usually a heat source.
• Basement conversion — ceiling height, egress windows, moisture management and a separate entrance are the four things that decide whether it is possible.
• Bonus room over the garage — check the existing framing first; garage roofs were rarely designed to carry a floor.

Utilities are the hidden cost

Sewer capacity, side-sewer routing, water meter size, and whether your electrical service can carry a second dwelling are the items that quietly move an ADU budget. We get those answers during feasibility, before you commit to a design.