Step-by-Step Guide

The primary step is to check the local zoning laws and building codes specific to your property's location. Regulations vary significantly by city and county, even within the same state.

Already Own Property?

The most important consideration is whether your current lot is compatible with your plans.
Define your use: Determine the purpose of the structure (e.g., rental income, home office, family housing) as this will shape the size, layout, and utility requirements.
Verify zoning and lot eligibility: Contact your local planning or building department (e.g.; for Black Diamond, this would be the City of Black Diamond Planning Department).
Confirm your property's zoning designation (e.g., single-family residential).
Ask if Accessory Dwelling Units (ADUs) or similar structures are permitted in your zone and if there are specific requirements for detached vs. attached units.
Check for minimum lot size requirements, floor area limits (e.g., up to 1,000 sq ft is common in parts of WA), height limits, and setback rules.
In King County, up to two ADUs (attached or detached) are allowed per lot in urban areas.
Assess property-specific factors: Consider the topography, soil type, and existing utility access (sewer, water, electricity).
Check for restrictions: Review your property's title and any Homeowners Association (HOA) bylaws for additional limitations or restrictions.
Consult professionals: We have design specialists to help you get the building you want, an architect, engineer and homebuilder who specializes in ADUs. We can help evaluate your site's feasibility and navigate the permitting process.

If you are looking for a new property
If you need to find a new piece of land, the same zoning rules apply.
Use specialized platforms: Websites and apps like Tiny House Listings often have filters for land that is already zoned for tiny house use or has fewer restrictions.
Utilize general real estate sites: When using sites like Zillow or Realtor.com, filter for lot size and always verify the zoning with the local planning department before making a purchase.
Work with an agent: Consider using a real estate agent who is familiar with ADUs/tiny homes and can use specific fields in the MLS (Multiple Listing Service) to find suitable properties.
Explore communities: Look into established tiny house communities, which often have pre-approved lots for rent or sale.

Key Action Items

Contact local authorities: The most reliable information will come directly from the your city's planning and building departments. They can provide specific guidelines and help you determine what is possible for your location.
Use online tools: Some municipalities (like Seattle, as an example, through their ADUniverse website) offer online tools to help homeowners assess their property's eligibility and find pre-approved designs, which can expedite the process.

Permitting

You will likely need a permit for your building, if it will be used as a habitable space such as an office, not just storage. In many areas, sheds larger than 120 square feet, those with electrical or plumbing, or those intended for human occupancy require a permit. You will need to check with your local building department for their specific regulations, as permit requirements can vary by size, location, and intended use.

Key factors that require a permit

Human occupancy: A shed or office intended for use by people, rather than just for storage, almost certainly requires a permit.
Size: A structure larger than 120 (200 depending on area) square feet typically requires a permit.
Utilities: If your office will have any electrical or plumbing work, you will need separate permits for those.
Location: Being near an environmentally critical area (ECA) or certain property lines may require a permit even for smaller structures.

What to do before you start

Contact your local building department: This is the most important step to ensure you comply with all local rules and avoid potential fines. Your local city building department website should be your first stop.
Check zoning and setback requirements: Make sure the building will not violate any zoning laws, such as being too close to property lines.
Be prepared to submit plans: If a permit is needed, you will likely have to submit detailed plans of the structure, including its dimensions, floor plan, and utility information.

The size you need depends on the building's purpose, but for a shed, 8'x10' is good for basic storage, while a 12'x12' or larger can accommodate big equipment. A home office might range from 8'x10' for a small desk to a 12'x16' for more furniture. For an ADU or tiny home, sizes are often in the 500-700 sq. ft. range, but this varies widely by location and is subject to local zoning laws that may limit size, height, and setback, so it's crucial to check with your local building department.

Sheds
Basic Storage: An 8'x10' or 8'x12' shed is suitable for garden tools and supplies.
Larger Equipment: A 10'x12' or 10'x16' shed is better for storing items like a riding mower or small tractor.
General Purpose: A 12'x12' is often a good fit for a larger yard.
Home Office
Minimalist: An 8'x10' is functional for a desk and basic workspace.
Spacious: A 12'x16' provides ample room for multiple desks, a sofa, and additional storage.
Accessory Dwelling Unit (ADU) and Tiny Home
Local regulations: ADU and tiny home sizes are highly dependent on local zoning laws.
Common range: Many municipalities that allow ADUs permit sizes in the 500-700 sq. ft. range, but you must check with your local building department.
Examples: Some areas may have specific size limits, such as Woodland allowing ADUs between 300 and 800 sq. ft., while Seattle limits them to 1,000 sq. ft. in some zones.
Key considerations for all structures
Intended use: The primary function will dictate the required square footage.
Local codes: Always check local zoning and building codes, which may have regulations on size, height, and setbacks from property lines.
Foundation: Remember to account for foundation size, which should be larger than the building itself.
Trailers: Key regulations for road-legal tiny homes
Classification: The home must be designed to be pulled behind another vehicle and licensed as a recreational vehicle (RV) or PMRV.
Size limits: They must be under 400 square feet to avoid needing special permits for transport. For standard highway travel, the dimensions are generally limited to 13.5 feet tall and 8.5 feet wide.
Building codes: While on wheels, they must meet RV safety standards (like ANSI A119.5) and be built to the Washington State Building Code.
Trailer requirements: The trailer must be properly registered, and the home must have appropriate lighting and braking systems.
L&I certification: For road legality, homemade RVs require an L&I RV inspection and insignia before they can be licensed.
Temporary use: Being classified as an RV generally means they are approved for temporary or recreational use, not as a permanent dwelling on a foundation.
How to ensure compliance
Work with us because we are a certified builder: Choosing a builder experienced in building RVs or PMRVs can help ensure the home meets all the necessary safety and building codes.
Consult local authorities: Check with your local city or county zoning and building departments, as rules can vary by jurisdiction.
Get inspections: Ensure your tiny home on wheels receives the required L&I inspection for RVs to get the necessary insignia for licensing and registration.