Residential Building Permits

Residential permits include:

  • Single Family Homes
  • Duplexes
  • Accessory Buildings
  • Mobile-Manufactured Homes
  • Private Storage Structures
  • Garages
  • Decks
    Retaining Walls
  • Fences
  • Docks
  • Swimming Pools
  • Mechanical
  • Plumbing

Townhomes and multifamily structures are considered Commercial Buildings.


The links below will help you find out what items you will need to get started with the permitting process.  For information on how to apply for a permit, refer to the Permitting page.

Click the image below to watch Mary's Permitting Story

Mary's Permitting Story image
Snohomish County regulates the contruction of many different types of buildings. Most structures require the applicant to submit a building permit application and site development plan. Residential building permits can be divided into four basic categories:
  • Single Family Residential (RK)
  • Manufactured Homes (MH)
  • Accessory Buildings (AB)
  • Other residential permits
Common examples are non-habitable structures under 400 square feet in rural zones, non-habitable structures under 200 square feet in urban zones, and uncovered decks contructed 30 inches or less from ground level. Please refer to Common Building Permit Exemptions (Assistance Bulletin #74) for other projects that are exempt from building permit requirements. Please keep in m ind that exempt structures my not require building permits but they must still comply with distances from property lines as well as environmental regulations.

Because each project is unique in its overall design, size, and configuration and is also distinctive as to property location each of these factors may trigger additional requirements. Some properties have specific requirements based on environmental factors which will have an impact on the development proposal. Other projects will have additional requirements based on specific thresholds of the project design such as the total amount of clearing, road length, slope of the property and the total amount of impervious surface created by the development. Zoning, setbacks, and bulk and dimensional requirements may also impact proposed projects. Based on your specific proposal you may be subject to one or more of the following:



Parcel specific

Some properties have specific requirements for development. Parcel Specific requirements may include:

New Access Permits

Verification of Legal Lot Status

Resource Land Notification Requirements



Project Specific

There are elements of the construction process that may or may not be required for your projects. These are based on the overall design of your proposed development. Examples include: total amount of new impervious surface you are proposing, road construction, number of trees you need to remove to build the structure, the amount of clearing or grading required for your project will affect the type of information you will need to provide and submit with your building permit application.

Click on the following to see if your project will requires these additional permits/approvals

Land Disturbing Activity Permit

Timber Harvest Permit



Environmental Approvals

Environmental regulations are designed to protect natural resources by limiting development and/or mitigating for project specific impacts. These regulations are established based upon best available science to determine buffer widths, setbacks, health and safety measures as well as outline appropriate mitigation measures for impacts to these areas.

The Critical Area Regulation of the county code is divided into sections based on the resource environment. Development is regulated within flood hazard areas and along state shorelines.

In addition some residential projects are subject to compliance with the State Environmental Policy Act (SEPA). This legislation is designed to identify impacts to the natural environment but also evaluate impacts to the human environment. Projects subject to SEPA will require public notification and need to complete an environmental checklist to be submitted with application materials.

SEPA Checklist

SEPA Review for Residential Improvements

Visit the following links to determine if your project is subject to any of the following additional environmental requirements:

Critical Areas

Shoreline Areas

Flood Hazard Areas

Mobile and manufactured homes require similar but sometimes different requirements than traditional houses and buildings. Since mobile and manufactured homes are designed and built in a factory, Washington State's Department of Labor and Industries (L&I) is responsible for the review and inspections of these buildings.

When placing these types of buildings in Snohomish County, PDS is responsible for the land and foundation portions only. Any interior alterations to the existing structure is regulated by L&I. Any additions added to the external structure is regulated by PDS.



PDS Requirements

Mobile-Manufactured Home Permit Submittal Checklist (PDF)

Mobile-Manufactured Home Application (PDF)

Mobile-Manufactured Home Plan Review Specification Form (PDF)



Assistance Bulletins

Building Permit (Manufactured/Mobile Homes) #36

Mobile Home Park Zone #80



Labor and Industries (L&I) Requirements

L&I Mobile/Manufactured Home webpage

Alterations regulated by L&I

Demolishing a Mobile/Manufactured Home

Converting a Mobile Home into Storage