Home Addition Plans and Permits

An addition is often the answer. It could be a primary suite, a bigger kitchen, a family room, or a second story on a rambler. Getting it permitted takes accurate drawings of the house you have now, a design that ties into it, energy code paperwork, and usually some structural engineering. Build Sherpas handles that for homeowners and contractors in Pierce and King County.

Start your addition with our contact form or call (253) 799-0606 or email office@dowengineeringpllc.com

1. First call. You tell us what you want to add. We look up your zoning, setbacks, and lot coverage so we know what fits.

2. Measure the house. We measure what is there and draw it. The addition plans are built on this.

3. Layout options. We sketch a few ways the addition could fit your lot and roof lines, then refine one with you.

4. Permit set. Site plan, existing and new floor plans, elevations, sections, and the Washington energy code (WSEC-R) forms.

5. Engineering. Most additions need beams, footings, or bracing designed by an engineer. Dow Engineering PLLC, in the same Sumner office, does that and stamps it when the city or county requires it.

6. Submit and answer comments. We submit the permit and respond to plan review comments until it is ready to issue.

Primary suites and bedroom additions

Kitchen and family room bump-outs

Second stories on single-story homes

Garage additions, or turning a garage into living space

Remodels that move walls, windows, or the roof line

Setbacks and lot coverage. The yard often looks bigger than what the code lets you build on.

Old unpermitted work. If a past owner closed in a porch or finished a basement without a permit, plan review may ask about it. Our Already Built Permits page explains how that is handled.

Septic, wells, and critical areas. Rural lots in Pierce County may need extra review.

Energy code. New space has to meet the current code even if the rest of the house does not. See our Energy Code page. Some jurisdictions want an air leakage test at final.

We check for these early so they do not turn into correction letters later.

Sumner, Puyallup, Bonney Lake, Tacoma, Auburn, Kent, and the rest of Pierce and King County. See Pierce & King County Permits for how each jurisdiction tends to run.

We do not build. You pick the contractor, or you run the job yourself as an owner-builder. If you want help with that, see Build Consulting. Planning a backyard cottage instead? See ADU and DADU Plans.

Do I need an engineer for an addition? Usually for part of it. New beams, footings, and wall bracing often need engineering. We bring in Dow Engineering PLLC when it is required.

Do I need an architect? Most single-family additions in Washington do not. A designer can prepare the drawings. We will tell you if your project is an exception.

Can you draw a remodel with no addition? Yes. Remodels that move walls or change structure follow the same steps.

What should I send to get started? Your address, photos of the house and the area you want to change, any old plans or a survey, and a list of what you want.

Will you work with my contractor? Yes. Bringing your contractor in early usually saves revisions.

Does my addition need a blower door test? It depends on the jurisdiction and the size of the work. If it does, WA Blower Door can test it.

Start your addition with our contact form, or call (253) 799-0606, or email office@dowengineeringpllc.com.

Build Sherpas, a trade name of Dow Engineering PLLC, 16202 64th St E Ste 117, Sumner, WA 98390. By appointment.

Related: Dow Engineering additions and remodels, Architectural, Permitting