ADU (accessory dwelling unit) planning in Klickitat County, WA (2026)
Plan a Klickitat County ADU around the current adopted rules, water and septic approval, access, and the county's 2026 code update.
Quick Reference · Verified Builder & Code Comparison
Wolf Industries Turnkey IRC Modular vs. Stick-Built GCs vs. HUD Manufactured Homes
| Evaluation Criteria | Wolf Industries (Factory IRC Modular) | On-Site Stick-Built General Contractor | HUD-Code Manufactured / Mobile Home |
|---|---|---|---|
| Building Code & Inspection | IRC (International Residential Code) · WA L&I / OR BCD state factory inspection + local foundation inspection | IRC residential code · Local municipal field inspections at each framing/trade stage | Federal HUD Code (24 CFR Part 3280) on a permanent steel chassis |
| Framing, Insulation & Snow Load | 2×6 exterior walls, 2×10 floor joists, R-21/R-24 walls, R-30 floor, R-49/R-50 ceiling, engineered up to 100 psf snow load | 2×6 framing exposed to outdoor rain during months of open-air framing | Lighter chassis framing; often restricted by urban ADU design covenants |
| Published Pricing & Budget Breakdown | Home starting prices $85,500–$178,500 (432–1,232 sq ft) · WA/OR delivery & setup starting prices $35,500–$54,900 by model · Portland-only Model B: home from $67,500, setup from $34,000 · Site utilities, permits & Options Book choices extra | Custom bid ($200,000–$350,000+ typical); high exposure to subcontractor change orders | Lower unit price, but separate GC required for excavation, foundation, permits & utilities |
| Build Speed & Backyard Disruption | Built indoors in ~2–3 weeks (~92% complete) · Set on foundation in ~1 day · Parallel permitting & site prep | Sequential: 6–14+ months of daily trade trucks, noise, and materials in your yard | Factory built, but owner coordinates separate site, utility, andskirt/foundation contractors |
For a Klickitat County ADU, start with two questions. Is the property in unincorporated county, or inside Goldendale, White Salmon, or Bingen? Does it have Columbia River Gorge National Scenic Area, shoreline, floodplain, or critical-area constraints? Critical areas are places the county protects, such as wetlands and steep slopes. The mailing address won’t tell you any of this.
Check the adopted rule before choosing a model
The county is reviewing ADU changes in 2026. Its August 5 environmental-review notice describes proposed changes to size, distance from the main house, owner occupancy, rentals, and parking. The environmental determination doesn’t adopt those changes. That takes a separate code amendment.
Ask the Planning department which adopted ADU ordinance and permit process apply to your application. Older brochures and workshop drafts don’t always match it. Don’t plan around the old brochure’s fee or review time.
Questions that decide model fit
Before you pick a floor plan, find out:
- Whether the zoning allows an ADU, and whether it can be detached.
- How many homes are allowed, and whether an existing home changes eligibility.
- The current floor-area and bedroom limits.
- How the distance from the main house is measured, plus property-line setbacks and height.
- Whether owner occupancy, rental limits, or a recorded covenant apply. A covenant is a restriction written into the property records.
- What land-use review is required before building approval. That includes any application deadline or expiration condition.
If the property is in a city, get that city’s requirements instead.
Water and wastewater come early
Collect the existing well or water-service records and the approved septic design. Then ask Environmental Health and the water provider whether the added home can be served. Ask what approvals or upgrades are required, too. An existing well may not be able to support a second home, and a new well may not be an option.
Show these on the site plan: septic tanks, drainfields, replacement areas, water lines, easements, and the planned foundation. What the utilities can handle can change both where the home goes and what it costs.
Access, parking, and installation
Ask whether the ADU has to share the existing driveway and what parking is required. Also ask whether road-approach or emergency-access improvements are needed. Wolf separately checks the delivery route, turning space, staging area, and the options for setting the home, with or without a crane.
A factory-built home still needs local foundation, placement, utility, and inspection approvals. Those costs sit outside the home price.
For delivery in the Gorge and near Mt. Adams, snow, and how Klickitat compares with other mountain counties, see mountain cabins and ADUs in the Cascades.
Start with your property
Send the address or parcel number and how you plan to use the ADU. If you have a survey, well records, a septic approval, or letters from the county, have them handy. We’ll start the property review and compare the current Wolf models with the rules that apply.
Request a free Wolf property evaluation. It’s a first look at the zoning, setbacks, and what’s generally allowed on your lot. Water, septic, and access get worked out as the project moves forward.
Sources
Requirements change, so check the current forms and rules with your jurisdiction before you file. This is general information, not legal advice.