Building permits, zoning and septic in Town of Cathlamet, Washington

At a glance

Building permits

Required for new construction and structural modifications¹

Zoning

Town zoning applies inside Cathlamet limits²

Application counter

Submit building-permit forms and applicable fees to Town Hall³

Septic installation

County Health and Human Services; licensed design required⁴⁵

Owner-builder

State contractor-registration exemption is conditional; building approval still matters⁶¹

Wells

State groundwater exemption has limits and does not approve a town well site⁷

Who to call

Contact details are copied from each office’s official page and were checked against it on October 14, 2026.

Do you need a building permit in Town of Cathlamet, WA?

Cathlamet requires a building permit for new construction or structural modifications inside town limits.¹ Cathlamet applicants must complete the appropriate forms and submit applicable fees to Town Hall before a building permit is issued.³ Start by describing the proposed work to Town Hall and asking which application forms and inspections apply. Cathlamet’s website offers building and land-use resources, while Washington’s state building code applies in cities and counties, subject to statutory exceptions and authorized local amendments.⁸⁹

Who handles building applications in Town of Cathlamet?

Town Hall is the submission point for Cathlamet building-permit forms and fees; submit them during regular business hours.³ The Town Hall departmental page lists 375 2nd Street, Cathlamet, WA 98612 and 360-795-3203 x2.¹⁰ Call before visiting to confirm the application counter location and ask for planning or building assistance. Town Hall lists planning and zoning among its services, and the town’s Building & Land-Use page provides the application route.¹⁰⁸

Does Town of Cathlamet have zoning, lot-size and setback rules?

Cathlamet has municipal zoning under Title 18 of the Cathlamet Municipal Code.² Unincorporated Wahkiakum County has no county zoning; that answer does not describe land inside Cathlamet.¹¹ For land outside town limits, use the Wahkiakum County guide for the county’s answer.¹¹ We could not confirm Cathlamet’s district-specific minimum lot size, setbacks, lot coverage or building height. Ask Town Hall to identify the parcel’s district and supply its current dimensional standards before choosing a house footprint. Cathlamet also regulates subdivisions under its municipal code.¹²

How do septic permits work inside Town of Cathlamet?

For a Cathlamet project using an on-site sewage system, Wahkiakum County Health and Human Services issues septic installation permits for new construction and repairs.⁴ Applications require design copies prepared by a licensed on-site wastewater treatment system designer or professional engineer.⁵ The county requires test pits so the county and designer can evaluate whether a septic system can be installed and which type is needed.¹³ Ask Town Hall about sewer service and connection requirements before commissioning a septic design. Washington allows or requires public-sewer connection in specified circumstances, including certain failing systems and development subject to local requirements.¹⁴

Can you live in an RV or tiny home in Town of Cathlamet?

We could not confirm Cathlamet’s rules for residential RV occupancy, temporary camping or tiny-home occupancy. Ask Town Hall whether the proposed use is allowed in the parcel’s zoning district and what approvals are needed before buying an RV or ordering a tiny home. Cathlamet has town zoning and requires building permits for new construction and structural modifications.²¹ Washington’s statewide building code also applies inside cities, subject to statutory exceptions and authorized local amendments.⁹ Request a written answer covering the specific structure, location, sanitation plan and intended duration.

Building a home in Town of Cathlamet: what are the steps?

Start with these questions before committing to construction:

1. Ask Town Hall to confirm the parcel’s zoning district and proposed residential use; Cathlamet has municipal zoning.²
2. Ask about water and sewer service. If septic is proposed, contact Wahkiakum County Environmental Health about the design and site evaluation.⁵¹³
3. Complete the required building-permit forms and submit applicable fees to Town Hall before permit issuance.³
4. Ask the building official for the inspection schedule and occupancy approval requirements. Under Washington’s residential energy-code inspection rule, a building must receive a final inspection and cannot be occupied until approved.¹⁵

Watch-outs

• Cathlamet’s zoning applies inside town limits; the absence of county zoning describes unincorporated Wahkiakum County.²¹¹
• Cathlamet has municipal zoning; we could not confirm residential RV or tiny-home occupancy, so ask Town Hall for a parcel-specific answer before purchasing.²
• A Washington groundwater permit exemption does not remove other local requirements or approve a well site; ask Town Hall and Ecology before planning a private well.⁷

Sources

1. Building & Land-Use - Town of Cathlamet (Town of Cathlamet), quoted and re-checked
2. Building & Land-Use - Town of Cathlamet (Town of Cathlamet), quoted and re-checked
3. Building & Land-Use - Town of Cathlamet (Town of Cathlamet), quoted and re-checked
4. On-Site Septic System Permits, quoted and re-checked
5. On-Site Septic System Permits, quoted and re-checked
6. RCW 18.27.090 — Exemptions (Washington statewide rule), quoted and re-checked
7. Groundwater permit exemption (Washington statewide rule), quoted and re-checked
8. Town of Cathlamet Building & Land-Use (townofcathlamet.com)
9. RCW 19.27.031 — State building code—Adoption—Conflicts—Opinions (Washington statewide rule), quoted and re-checked
10. Town of Cathlamet Town Hall (townofcathlamet.com)
11. FAQs • Is there zoning in Wahkiakum County?, quoted and re-checked
12. Building & Land-Use - Town of Cathlamet (Town of Cathlamet), quoted and re-checked
13. Wahkiakum County Health & Human Services - Environmental Health (co.wahkiakum.wa.us)
14. WAC 246-272A-0025 — Connection to public sewer system (Washington statewide rule), quoted and re-checked
15. WAC 51-11R-10500 — Section R105—Inspections (Washington statewide rule), quoted and re-checked

Written October 14, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.