Snohomish County ADUs and Home Additions
How Homeowners Benefit from ADUs and Home Additions
Over the last few years, both public opinion and local legislation regarding ADUs – short for “accessory dwelling units” – have evolved. Today, Washington State allows homeowners with sufficiently sized lots to build up to two 1,200 square foot ADUs. Other Western states like California and Oregon have passed similar laws. In 2021, California Governor Gavin Newsom signed Senate Bill 9 – which permits up to four ADUs on a single residential lot. Earlier this year, Washington State Governor Jay Inslee also eyed new legislation expanding ADU permissions to alleviate our housing crisis. East Coast states like Massachusetts and New Hampshire are finally weighing changes to their laws too. Of course, there are critics of ADUs and home additions on both coasts. Critics often argue that increased ADU construction will lead to more short-term rentals, traffic jams and parking shortages. However, ADUs offer a number of benefits to both homeowners and the neighborhoods in which they are built. From passive income to additional living space, follow below to learn all about the trend towards ADUs and home additions in Washington State.

Answers to FAQs About ADUs and Home Additions in Snohomish County
What is an ADU?
An ADU is an accessory dwelling unit that can either be attached to the primary dwelling or freestanding elsewhere on the property. AADUs are attached accessory dwelling units while DADUs are detached accessory dwelling units. ADUs are usually between 800 and 1,200 square feet in built footprint, while JADUs can be between 150 and 500 square feet.
JADUs are “junior accessory dwelling units” built within a property’s primary dwelling. Because they share walls with the primary dwelling, JADUs need not have a full kitchen or bathroom within what is essentially a studio apartment. Both ADUs and JADUs are subject to local building codes, even when an existing structure is converted to create new living space. Thus, homeowners must also secure permits and arrange for inspections. Check with your local planning department or your remodeler for more information about building an ADU or JADU to code in Washington State.
Can I Use My ADU As a Short-Term Rental?
Short-term rentals like those listed on Airbnb and Vrbo are a pain point for both critics and proponents of ADUs and JADUs. Critics of eliminating single family zoning and allowing homeowners to build ADUs in their backyards make one point. They believe that short-term rentals are far too disruptive to quiet suburban neighborhoods. Proponents of eliminating single family zoning and allowing homeowners to build ADUs make another point. They argue that short-term rentals are also harmful because they reduce the number of affordable housing units.
A primary goal of legalizing ADUs and JADUs in California, Oregon and Washington State is to alleviate the affordable housing crisis. As such, recent legislation in cities across all three states – especially in Los Angeles and San Francisco – has tightened restrictions on short-term rentals. Requirements in Washington State are somewhat looser than those in California. ADUs in Seattle can be listed as short-term rentals as long as each owner obtains a short-term rental operator license. Property owners must also post a current business license tax certificate from the city at their place of business.


Is It Better to Add On or Build Up?
Whether you choose to build up or add on will depend on your budget and the timeline for your project. It will also depend on the planned size of your addition, the age of your home and the square footage of your property. The addition's intended use will also dictate whether adding on or building up makes more sense.
From a financial perspective, building out tends to be less expensive than building up. It is also usually less disruptive, because homeowners need not move out while construction is underway. Though typically the most expensive option, building a detached ADU is least disruptive to one's everyday life. This is because construction is isolated to another part of your property entirely. Consult with your remodeler before deciding on a second story addition, attached ADU or detached ADU.
Is An Addition Worth the Money?
Homeowners often ask whether building an addition or detached accessory dwelling unit is worth the money. As long as the ADU or other addition is constructed carefully, lawfully and fully to code, it should add value to your property. According to Charlie Melvin with full service design-build firm Cali ADU, the average LA homeowner could recoup 88% of their investment in an ADU. Melvin notes that a 1,000 square foot detached ADU could add "an average of $470,000 to your property value." Not only do ADUs and additions increase the amount of livable square footage on your property. They also offer passive income if used as a rental unit.
However, the cost and ROI of your addition or ADU both depend heavily on your local housing market. A garage conversion might return less, because it eliminates valuable storage and covered parking space. Additions that obstruct outdoor space could also return less of your investment upon sale.
What is a Bump-Out Addition?
Building a bump-out addition is one of the most popular ways homeowners increase their primary dwelling's square footage. Lee Wallender and Lexie Pelchen explain these remodeling projects in their article "How To Plan A Bump-Out Addition To Your House" for Forbes Advisor.
According to Wallender and Pelchen, "a bump-out is a minor addition to a house." Bump-outs will increase the home's "total square footage but [will not] reach the scale of a full addition." They note that a bump-out could be "as small as two or three feet that push out the side of the house." Alternatively, a bump-out could be "as large as a single room." Minor bump-outs are especially common in updated bathrooms and kitchens of small older homes. Keep in mind however, if the foundation or roof needs to be altered to accommodate a large bump out, the cost will increase significantly.
Will An Addition Increase My Property Taxes?
Unfortunately, most major renovations that involve structural alterations or added square footage increase property taxes. This is especially true of renovations that bump up your home's livable space. Keep in mind that only certain renovations trigger property tax reassessments.
For example, detached ADUs usually trigger a partial reassessment. This means that the new unit is assessed as a separate structure. Property taxes related to the original single family home should remain unchanged.
What are the Costs?
Download our free Snohomish County Home Remodeling Cost Guide to learn more about the costs and considerations of remodeling a:
- Kitchen
- Bathroom
- Whole home
- Exterior of home
- Home addition or ADU**

What Are the ADU Laws in Snohomish County?
Until recently, Snohomish County limited homeowners to a single ADU per lot. It also required extra off-street parking, demanded evidence of owner-occupancy and restricted where rural homeowners could build ADUs on their properties. Last summer, the Snohomish County Council altered existing ADU regulations in urban, suburban and rural areas of the county.
In his June 2021 article “Snohomish County Liberalizes Backyard Cottage and Basement Apartment Rules” for The Urbanist, Stephen Fesler summarizes recent reforms. Fesler writes that urban homeowners in Snohomish County may now build “one AADU and one DADU…per lot with a single-family residence.” Rural homeowners in Snohomish County can build one ADU, as long as the lot is large enough to accommodate the new dwelling unit.
Mobile homes classified as detached ADUs “are only permitted on lots that are 10 acres in size or more.” Attached and detached ADUs may be no larger than 1,200 square feet “excluding garages, porches, and unfinished basements.” In passing these new reforms, the Council eliminated parking requirements for urban areas. The Council also reduced off-street parking to a single space per ADU in rural areas.
Three Benefits of Building an ADU or Home Addition
There are three key benefits to building an ADU or home addition. First, building an ADU or home addition increases your property’s livable space. Second, building an ADU or home addition could provide you and your family with passive income if leased to tenants. In some cases, the passive income earned by renting out the unit could cover the cost of construction within a few years. Third, building an ADU or home addition usually adds value to your property – resulting in a bigger profit when you eventually choose to sell.


Build Your Snohomish County ADU or Home Addition with VanderBeken Remodel
Are you considering an ADU or home addition to boost your property's value, increase livable square footage or provide passive income? If you are a Snohomish County homeowner, consider VanderBeken Remodel for your upcoming project. Our design-build remodeling company specializes in bathroom renovations, kitchen updates, additions and whole home remodels. For more information about our approach to home additions in Snohomish County, read through our process. To begin the discussion about your home addition or ADU, schedule a call with us.
VanderBeken Remodel Service Area for ADUs and Home Additions in Snohomish County
Our service area for ADUs and Home Addition remodels currently includes:
- Edmonds, WA
- Everett, WA
- Lake Stevens, WA
- Marysville, WA
- Mill Creek, WA
- Mukilteo, WA
- Snohomish, WA
Founded in 2007, VanderBeken Remodel is based in Marysville, WA and is passionate about building beautiful spaces for fantastic people in Snohomish County!

VanderBeken Remodel and all of their specialty trade partners were a pleasure to work with. They were clean, conscientious of our time, and even were great with our young boys.
Mr. & Mrs. L. Snohomish, Washington Master BathroomRon and Jen were committed to helping us build what we wanted. They asked great questions to set us up for success and followed up to make sure they delivered to our satisfaction. Remodels always have unexpected issues, and Ron helped us think through viable options to overcome the challenges. Ron and Jen are our go-to people for remodels. We will be calling in them again. We encourage anyone who feels strongly about getting good quality and thoughtful partnership to meet them.
Mr. & Mrs. P. Snohomish, Washington Carriage HouseThe Vanderbeken team just completed a major interior remodel project for us and we could not be happier with the results. We were impressed with the integrity their team brought to the process from beginning to end. Very important to us was their follow up and attention to detail. Finally, the quality of the workmanship was outstanding.
Mr. & Mrs. R. Camano Island, Washington Whole House RemodelVanderBeken Remodel met or exceeded my expectations regarding their skills, cleanliness, organization, and craftmanship. They were very professional and kept their word. It did not feel like there was a stranger in my home. They were great with my pets and respectful of my home.
Kerry Q. Marysville, Washington Kitchen RemodelI was very pleased with the work they did. Everyone involved did an amazing job and we are very happy with our kitchen!
Mr. & Mrs. S. Edmonds, Washington Kitchen RemodelThis is the third time we have hired VanderBeken Remodel to work on our home. In every project from converting a garage into living space with woodstove installation and granite surround, to building a detached carport, to this, our latest experience, adding over 1,000 sf to our house, leveling the yard and widening our driveway, VanderBeken Remodel has excelled in everything. Ron is personable, available, and fastidious in every detail. His dedication to quality and beauty is evident in every corner of our home. For ten years we planned our “dream home” and to see it crafted out under Ron’s expertise has been an amazing experience. It’s more beautiful than we ever imagined! We always recommend VanderBeken Remodel to everyone.
Mr. & Mrs. W. Monroe, Washington