Building permits, zoning and septic rules in Lewis County, Washington

At a glance

Building permit

Required for covered work in unincorporated Lewis County¹

Zoning

County zoning and critical-area review apply in unincorporated areas⁶⁷

Septic permits

Lewis County Environmental Health; Master Site Review comes first⁴⁸

Owner-builder exemption

Conditional contractor-registration exemption; permits still apply⁹

Water availability (wells)

Reviewed under the state's post-Hirst rules before a building permit issues¹⁰

Tiny-home occupancy

County rules were not confirmed; ask Community Development before siting one²

RV living

Long-term private-property occupancy was not confirmed; ask Community Development²

Permit fees

Published schedule; charges vary by permit, review, inspection, and project details¹¹

Road approach (driveway) permit

Required to connect to a county road; $350 plus a $50 administrative fee¹²

Who to call

Contact details are copied from each office’s official page and were checked against it on October 10, 2026.

Do you need a building permit in Lewis County, Washington?

Yes. Lewis County requires an application to the Building Official and the required permit before covered building and development work in the unincorporated county begins¹. The application must include the parcel's legal description or tax parcel number, assigned street address, owner and contractor information, current contractor-registration verification, and required fees¹. Washington's state building code applies in every county and city, including residential construction in unincorporated Lewis County¹³. Lewis County publishes permit fees that vary by permit type, valuation, occupancy, plan review, inspection, and other project details; state, mechanical, and plumbing charges are not included in the building-permit fee¹¹. Under the fee schedule effective January 1, 2025, the lowest building-permit fee is $30.85 for a valuation of $1 to $500, standard plan review is 65% of the base fee, and starting work without a permit costs double the permit fee¹¹. An owner working on their own property may qualify for Washington's contractor-registration exemption when the work is not for sale, demolition, or lease, but that exemption does not remove building, electrical, plumbing, or other permits⁹.

Who is the Lewis County building department, and how do you reach them?

Lewis County Community Development is the building, planning, zoning, and floodplain office for unincorporated Lewis County¹⁴. The office is at 125 NW Chehalis Ave, Chehalis, WA 98532, and its permit-center phone number is 360-740-1146¹⁴. Use SmartGov to submit an application, check permit status, or request an inspection¹⁴. Master Site Review is the first development step and identifies county, state, and federal permits that may apply; after approval, applicants can pursue septic, fill-and-grade, building, and other permits³. Inspection requests go through SmartGov only, and the daily cutoff is 6:30 a.m.; later requests move to the next day¹⁵. The available county material does not establish one inspection sequence for every project, so ask Community Development which inspections apply to your permit.

Does Lewis County have zoning?

Yes. Lewis County has an official zoning map for land under county jurisdiction, while incorporated municipalities may administer separate zoning rules⁶. Inside a city or town, ask that city's administrator, because its regulations may differ; in an unincorporated urban growth area, both county and city administrators may apply different parts of their codes¹⁶. Septic permits stay with Lewis County Environmental Health either way¹⁷. The county identifies its current official zoning map as effective October 1, 2025⁷. Ask Community Development to identify the parcel's district and allowed uses before designing a home, accessory dwelling, or short-term rental. County planning reviews proposals for both zoning and critical-area compliance². Road setbacks include 55 feet from the centerline where a county right-of-way is 60 feet wide or less, and 25 feet from the near edge where the right-of-way is wider than 60 feet¹⁸. Other setbacks depend on zoning or the applicable building-code table¹⁸. Minimum lot sizes for new subdivisions and segregations in the rural and resource districts run from 80 acres in Primary Forest Resource Land (with exceptions) and 20 acres in Local Forest Resource Land and Agricultural Resource Land, to 10 acres in Mineral Resource Land, and 20, 10 and 5 acres in the RDD-20, RDD-10 and RDD-5 rural development districts¹⁹. The RRC rural residential districts run from 10,000 square feet in RRC-A to 2 acres in RRC-E, and some other districts have no zoning minimum, so health code and available utilities decide lot size there¹⁹. In urban growth areas, residential minimums run from 2,500 square feet in RM to 7,500 square feet in AX²⁰. Lewis County's available rules do not provide complete countywide answers for accessory dwellings outside the proposed urban-growth-area designations, lot coverage, or building height, so get those parcel-specific limits from Community Development.

How do septic permits work in Lewis County?

Lewis County Environmental Health evaluates septic sites and test-pit soils, sets permit conditions, and issues on-site sewage permits⁴. New construction requires a sewage permit or evaluation application, a site project plan, and permission to enter⁸. Repair, replacement, alteration, connection, or reconnection can also require a permit; work outside the septic tank requires a permit, and tank replacement requires one⁸. A home or other building connecting to a permitted system installed more than one year before its building or mobile-home placement application needs a connection or reconnection permit⁸. A well that would serve more than one single-family residence needs a Lewis County Well Site Inspection Form, and Master Site Review approval comes before that application; an individual well is excluded from the form²¹. Request the construction final inspection through the county septic inspection line⁵. Only about 7.1% of Lewis County soils are rated without severe limits for a conventional drain field, so make septic feasibility an early check²². The county's available material does not confirm whether alternative off-grid sanitation systems are allowed; ask Environmental Health before planning one.

Can you live in an RV or tiny home on your land in Lewis County?

Lewis County's available rules do not confirm a general right to live long term in an RV on private property, a complete private-property camping rule, or a countywide tiny-home occupancy rule. The county's RV rules that we found cover RV parks and campgrounds, where the same party may occupy a camping site for no more than 210 consecutive days, and flood hazard zones, where an RV must stay fewer than 180 consecutive days, be fully licensed and ready for highway use, or meet the manufactured-home elevation and anchoring rules²³²⁴. Ask Community Development about the parcel's zoning, approved use, utilities, and permit path before buying an RV or tiny home for full-time occupancy⁶. Washington recognizes code-compliant tiny houses of no more than 400 square feet, including those built on wheels, but foundation, installation, location, and local permits still depend on the local building department²⁵. Lewis County defines a tiny home, also called an efficient dwelling unit, as a dwelling with living space, a bathroom and kitchen facilities and a total floor area of 220 to 1,000 square feet; that definition sets the size range, not a minimum for every dwelling²⁶. Lewis County includes RVs, trailers, yurts, homes, accessory dwelling units, duplexes, detached bedrooms, and similar structures in its short-term-rental program²⁷. Short-term rentals must register beginning January 1, 2026, with one calendar year to comply, and must have approved water, sewage treatment, onsite parking tied to bedroom count, and waste service or a secure receptacle²⁷. Short-term-rental treatment does not establish permission for permanent occupancy.

Building a home in Lewis County: what are the steps, in order?

1. Ask Community Development to confirm the parcel's zoning district, allowed use, critical areas, floodplain status, and setbacks²²⁸¹⁸.
2. Complete Master Site Review, the county's first development step; use Land Development Review for a subdivision or boundary-line adjustment³²⁹.
3. Confirm the water and wastewater path; county-managed systems use availability forms, while wells, septic, municipal service, and other public systems can follow separate reviews³⁰.
4. Obtain the septic evaluation and permit from Environmental Health⁸.
5. Apply for a road approach permit if your driveway connects to a county road: the county lists $350 plus a $50 administrative fee, then checks ownership and legal access, and you call the Area Supervisor for final inspection after installing the approach¹². A new private road or other new site access needs the appropriate application too³¹.
6. Submit the building application and pay the applicable building, review, trade, and state charges¹¹¹.
7. Request building inspections through SmartGov and the septic construction final inspection through Environmental Health¹⁵⁵.

What should you check before you buy land in Lewis County?

Confirm the zoning district and ask Community Development for the parcel's use, setback, critical-area, and floodplain constraints before relying on a seller's description²²⁸¹⁸. All development in a Lewis County floodplain requires a floodplain development permit, listed at $50 in the 2025 fee schedule, and an existing building is covered when improvements or repairs exceed 50% of its value, tracked cumulatively over 10 years³²³³. Confirm the actual water path because county-managed systems use availability forms, while wells, septic, municipal service, and other public systems can require different reviews³⁰. Order septic feasibility work early because only about 7.1% of Lewis County soils are rated without severe limits for a conventional drain field²². Verify legal access and whether a road-approach or private-road application is needed³¹. If you intend to divide the land, start with Land Development Review: the county distinguishes long plats, short subdivisions, large-lot subdivisions, and simple segregations by lot count and acreage²⁹. Lewis County's median property tax bill is about $2,433 a year, with an effective rate near 0.7%³⁴³⁵.

Watch-outs

• Master Site Review comes before the later building, septic, grading, and development applications, so budget time for that first review³.
• Washington's 2018 response to the Hirst decision can require proof of adequate water supply before Lewis County issues a building permit for land relying on a permit-exempt well; check Community Development's water-availability review before you buy well-dependent land¹⁰.
• An unpermitted or altered approach onto a county road is a misdemeanor under Washington law, and a driveway onto a state highway needs a separate state permit; confirm which applies before you build access to your parcel³⁶³⁷.
• Lewis County's available rules do not confirm long-term RV occupancy on private land outside RV parks and flood zones, private-property camping, or a countywide tiny-home occupancy rule; ask Community Development for a parcel-specific answer before relying on any of those uses⁶.

Sources

1. Lewis County Code, Title 15, quoted and re-checked
2. lewiscountywa.gov, quoted and re-checked
3. lewiscountywa.gov, quoted and re-checked
4. Septic Program, quoted and re-checked
5. Septic Program, quoted and re-checked
6. Zoning & Comprehensive Plan Maps - Lewis County GIS, quoted and re-checked
7. Zoning & Comprehensive Plan Maps - Lewis County GIS, quoted and re-checked
8. lewiscountywa.gov, quoted and re-checked
9. RCW 18.27.090 Exemptions, quoted and re-checked
10. Lewis County Community Development – Water Availability (Hirst Response) (lewiscountywa.gov)
11. Lewis County Fee Schedule, quoted and re-checked
12. lewiscountywa.gov, quoted and re-checked
13. RCW 19.27.031 — State building code—Adoption—Conflicts—Opinions (Washington statewide rule), quoted and re-checked
14. Lewis County Community Development (lewiscountywa.gov)
15. Building Inspections, quoted and re-checked
16. Zoning & Comprehensive Plan Maps, quoted and re-checked
17. Lewis County Environmental Health – On-Site Septic Program (lewiscountywa.gov)
18. Lewis County Code, Title 15, quoted and re-checked
19. Chapter 17.42: Rural Area Zoning Summary, quoted and re-checked
20. Article II: Zoning Standards, quoted and re-checked
21. Applications & Permits, quoted and re-checked
22. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
23. ecode360.com, quoted and re-checked
24. Chapter 15.35: Flood Damage Prevention, quoted and re-checked
25. Tiny Houses (Washington statewide rule), quoted and re-checked
26. Chapter 17.10: Definitions, quoted and re-checked
27. Short Term Rental Registry Process, quoted and re-checked
28. Floodplain Construction Rules, quoted and re-checked
29. lewiscountywa.gov, quoted and re-checked
30. lewiscountywa.gov, quoted and re-checked
31. lewiscountywa.gov, quoted and re-checked
32. Floodplain Construction Rules, quoted and re-checked
33. Exhibit A Category A/B Fee Schedule, quoted and re-checked
34. Median property tax bill: Bolthole Index county data
35. Effective property tax rate: Bolthole Index county data
36. RCW 36.75.130 — Approaches to county roads—Rules regarding construction—Penalty (Washington statewide rule), quoted and re-checked
37. RCW 47.32.150 — Approach roads, other appurtenances—Permit (Washington statewide rule), quoted and re-checked

Written October 10, 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.