In master-planned communities like Tahoma Terra and the Yelm Urban Growth Area, homeowners are taking advantage of Thurston County's expanded accessory dwelling unit regulations to build detached backyard cottages (DADUs) and garage guest suites for rental income or multigenerational living. Constructing an ADU in Yelm requires code compliance: 1-hour fire-rated drywall partitions (IRC Section R302), moisture-resistant bathroom gypsum boards, and high-vaulted ceiling taping. Solis Interiors provides turnkey ADU drywall hanging, mechanical taping, texture matching, and painting. In 2026, complete ADU drywall packages in Yelm range from $3,200 to $6,800.
The ADU Boom in Tahoma Terra & Yelm
With the passage of Washington State housing laws and updates to Thurston County Title 20 Zoning, Yelm homeowners in neighborhoods like Tahoma Terra and Mill Pond are adding detached cottages in their spacious backyards.
While detached cottages don't always share a party wall with the main home, local building inspectors enforce strict standards:
- Attached ADUs require full 1-hour fire separation from the primary home.
- Detached ADUs within 5 feet of property lot lines require 5/8" Type X fire-rated exterior wall assemblies under setback fire codes.
- Compact footprints mean open vaulted ceilings and intense bathroom moisture that must be addressed with the right drywall panels.
Solis Interiors handles your entire ADU drywall scope so you pass pre-rock inspection with zero delays.
What fire-rated drywall is required for detached and attached ADUs in Yelm?
Under IRC Section R302.1 and R302.3 and Thurston County Title 20, attached ADUs require a 1-hour fire-resistance rated drywall assembly (5/8" ASTM C1396 Type X) across all shared walls and ceilings, and detached ADUs located within 5 feet of property boundaries must feature 5/8" Type X fire board along exterior-facing walls.
Here is how Solis Interiors ensures a first-pass inspection:
- Intumescent Fire-Caulking: All electrical outlet boxes, plumbing penetrations, and mini-split lines cutting through Type X assemblies are sealed with certified red fire-stop sealant.
- Moisture-Resistant Purpleboard: We hang mold-inhibiting ASTM C1396 panels across all ADU bathrooms and kitchen wet walls, protecting compact spaces from humidity.
- High-Vaulted Ceiling Taping: Many Tahoma Terra cottages feature dramatic 12-to-14-foot vaulted scissor trusses. We use articulating scaffolding and high-tensile paper-faced composite corner beads that never crack under roof deflection.
ADU Drywall Assembly Requirements in Thurston County
| ADU Location / Component | Required Drywall Material | Code Compliance Purpose |
|---|---|---|
| Attached ADU Shared Wall & Ceiling | 5/8" ASTM C1396 Type X | Mandatory 1-Hour Fire Barrier (IRC Section R302.3) |
| Property Line Setback Walls (<5 ft) | 5/8" Type X Exterior Fire Wall | Lot line fire protection under IRC Section R302.1 |
| ADU Bathrooms & Laundry Areas | ASTM C1396 Moisture-Resistant | High humidity defense in compact footprints |
| Living Room & Bedroom Walls | 1/2" Standard Gypsum (Level 4 Finish) | Smooth wall or orange peel texture match |
2026 ADU Drywall Pricing in Yelm & Thurston County
| ADU Size & Scope | 2026 Yelm Cost Range | What Is Included in the Job |
|---|---|---|
| Studio / 1-Bedroom ADU (400 - 600 sq. ft.) | $3,200 - $4,800 | 5/8" Type X fire board, MR bath board, 3-pass taping, orange peel texture, primer |
| 2-Bedroom Detached Cottage / DADU (650 - 900 sq. ft.) | $4,500 - $6,800 | Complete hang & finish, vaulted ceiling staging, PVA primer, ready for trim |
| Turnkey Drywall & Interior Painting Package | +$1.20 - $1.80 / sq. ft. | Airless spray application of 2 coats commercial scrubbable interior paint |
Authoritative Building Codes & References
- Thurston County Community Planning: Title 20 Zoning & ADU Regulations
- International Residential Code (IRC): IRC Section R302: Fire-Resistant Construction
- Gypsum Association: GA-600 Fire Resistance and Sound Control Design Manual
Get an Itemized ADU Drywall Estimate in Yelm
Building a backyard ADU or mother-in-law cottage in Tahoma Terra, Yelm, or Thurston County? Text your floorplans to Jesus Solis for a detailed proposal within 24 hours.
- Direct Phone: (360) 350-8616
- Online Quote Request: Request ADU Drywall Bid
- Service Area: Tahoma Terra, Yelm, Rainier, McKenna, Lacey, Olympia.