AADU builder for Seattle and the Eastside.

Three reasons drive most AADU decisions in Seattle and the Eastside. First, lot constraints. A tight urban lot with critical-area triggers, mature tree canopy, or restrictive setbacks may not have room for a freestanding DADU but easily supports an addition with an AADU inside. Second, cost. Sharing the foundation wall, the roofline, and the utility runs with the existing house cuts a meaningful slice off the bid. Third, schedule. AADU construction is often 4 to 8 weeks faster than a comparable DADU because there is no second foundation pour and fewer separate utility runs. The downside is privacy: tenants share an exterior wall with the main residence and noise transmission requires careful acoustic detailing during framing.

Seattle's AADU code caps the unit at 1,000 sq ft of gross floor area, the same maximum as a DADU. Some lots qualify for the 1,200 sq ft bonus floor under tree-retention rules. The AADU footprint counts toward the lot's total coverage, so on lots with tight coverage caps the practical AADU size may be smaller than the maximum. Bellevue, Kirkland, Redmond, and Mercer Island all permit AADUs up to 1,000 sq ft. The unit must have its own kitchen, bath, separate entry, and meet code-required ceiling heights. We map your lot's specific buildable AADU envelope during the free feasibility visit.

Most jurisdictions allow shared utilities for AADUs as long as the connection is engineered for the combined load and the existing service can support it. That usually means a dedicated subpanel inside the AADU fed from the main panel (Seattle SDCI permits this in most zones), and a shared sewer lateral with separate cleanouts. Water service is typically shared. If the existing main panel cannot carry the second-unit load, a panel upgrade or a separate service is required. We evaluate the existing infrastructure during feasibility and engineer the right utility approach for your specific home.

Plan on 5 to 8 months from signed contract to certificate of occupancy for a typical Seattle AADU. The breakdown is roughly 3 to 4 weeks of design, 2 to 4 months of plan-check at Seattle DCI, and 2 to 4 months of construction. AADU construction runs faster than DADU because we are tying into existing framing and foundation. Eastside cities like Redmond and Kirkland generally compress permit timelines further. Aaron's crews build faster than the regional average, and we hold the schedule we put in writing.

AADUs typically run 15 to 25 percent less than a comparable DADU on the same lot because the foundation, roof, and utility runs are shared with the existing house. The variables that move the bid most are: how much existing wall and roof we can preserve versus rebuild, whether the existing electrical service supports the second-unit load, finish level, and any code-mandated upgrades to the existing house triggered by the addition (egress windows, fire separation, energy-code retroactive requirements). We deliver a written fixed-price contract after a free site visit so you can compare an AADU bid against a DADU bid line by line for your specific lot.