Twin Brothers Group — ADU & DADU Framing Contractor
Twin Brothers Group is a licensed and bonded framing contractor based in Washington State, serving King and Snohomish County. They specialize in framing accessory dwelling units, detached ADUs, garage conversions, and home additions for general contractors, ADU builders, and owner-builders throughout the greater Seattle area.
With Seattle now permitting up to two accessory dwelling units per residential lot, demand for backyard cottage construction has grown considerably. Twin Brothers Group positions itself as a dedicated framing subcontractor for this type of work, self-performing all framing with their own crews rather than subcontracting the labor out.
ADU Project Types They Frame
Twin Brothers Group handles a range of ADU and DADU framing scopes, including:
- Detached ADUs (DADUs): Stand-alone backyard cottages ranging from 400 to 1,000+ square feet. They frame walls, floors, and roof systems from stamped plan sets — including Seattle's pre-approved DADU plans — with full shear wall and hardware installation per structural drawings.
- Attached ADUs: In-law suites, basement conversions, and attached secondary units. Work includes structural modifications to existing framing, new bearing walls, and floor system upgrades while keeping the main structure weathertight.
- Garage Conversions: Garage-to-ADU conversions involving new floor framing over slabs, wall furring, insulation-ready framing, ceiling joists, and structural headers where garage doors are removed and windows are added.
- Home Additions & Second Stories: Room additions, second-story additions, and structural remodels, with new framing tied into the existing structure to match floor elevations, roof lines, and load paths per engineer drawings.
Converting a garage to an ADU in Seattle involves specific structural requirements — headers where doors come out, new floor framing over existing slabs, and ceiling upgrades to meet dwelling code. Twin Brothers Group bids this work accurately based on the actual plan set rather than generic estimates.
How Their ADU Framing Process Works
Twin Brothers Group follows a structured process designed to keep ADU and DADU projects on schedule:
- Scope & Bid: Submit a permitted plan set — including pre-approved DADU plans — and they return a detailed framing bid within 48 hours, including scope, exclusions, and schedule.
- Site Coordination: ADU lots are typically tight. Before work begins, they plan material staging, crane or telehandler access, and delivery timing around the specific backyard site conditions.
- Frame & Dry-In: Walls, floor systems, roof framing, and sheathing are completed — typically within 2 to 4 weeks for a standard DADU. Framing is completed to pass inspection on the first attempt.
- Close-Out: Punch items are addressed promptly so MEP rough-in, windows, and siding can follow without delay, with a clean handoff to the next trade.
Most of their ADU and DADU framing work comes through general contractors and ADU builders, though they also work directly with owner-builders who are managing their own permits. Both receive the same written bid process and crew standards.
Twin Brothers Group installs all Simpson hardware, holdowns, and shear wall systems per structural drawings, and coordinates directly with structural engineers when field conditions require it. Their recent accessory dwelling work includes a backyard DADU in West Seattle, a combined single-family residence with ADU and DADU, and home additions across the Seattle metro area.
For ADU builders or design-build firms with a steady pipeline of projects, Twin Brothers Group offers repeat-builder scheduling, reserving crew capacity for partners with ongoing work. They serve the Seattle, Bellevue, Kirkland, and broader King County region, as well as Snohomish County.
