ADUs in Clark County, WA

Real Estate Broker/Owner with ViewHomes of Clark County - Nature As Neighbors
ADUs in Clark Coiunty


ADUs in Clark County

Since we specialize in multigen homes, we often receive requests for information about Auxiliary Dwelling Units (ADUs) in Clark County, WA. ADUs can be a desirable alternative for multigen living, provided you know the guidelines in your local area. Recently a rural homeowner on 5 acres asked about the ADU regulations in her area, so we thought we'd review the current status of ADUs in Clark County.


ADUs Are Legal, But...

The basic rule is, ADUs are legal in both urban and rural areas, but the allowable buildings are different. If you are in city limits, you are allowed - within certain guidelines - to add a separate structure up to 800 SQFT. An ADU within city limits may be larger if incorporated into an existing structure.* In rural properties, separate ADU structures are simply not allowed.


Rules for Rural ADUs

For purposes of this article, we will concentrate on rural properties and county guidelines. Any residential home on at least one acre can add an ADU, provided it is within or attached to an existing residential structure. This usually means upgrading a basement, attached garage, or adding to the current structure - as long as it is attached. There is no provision for adding a separate ADU structure, no matter how large the property.


Multigen Families Like ADUs

Many multigen families want privacy and separate living areas so they're not stumbling over each other. The ideal solution for that is to convert an existing daylight basement with separate entrance, as we did with our home. The other alternative is to expand the existing house with an attached structure - often, a simple breezeway or deck will be sufficient to pass code. These are issues you should review with your local permit department.


Having said that, we have seen homeowners who had built separate structures called "studios" or "offices" with room for bedroom, bathroom, and kitchenette sink with counters. This is allowed, and will be permitted for occupancy, but it cannot have a stove. There are, of course, other building permit restrictions that can apply.


First Things First

If you are considering a rural ADU, the first issue is whether the existing septic system and well can support an additional bedroom or two. The state's chart shows accepted guidelines for septic sizing:



You will need to check with your local Health Department to see if your current system will support an ADU. Their analysis will include not just the tank size, but also the capacity of the drain field. If neither is sufficient, you will need to expand the current system, or install a separate system.


Some homeowners decide to "decommission" a bedroom, and assign it to the new ADU. This is tricky because, though legal, could present problems at resale or for appraisers down the road. Also, if you decide to build a "studio" without a stove, you will not be able to consider it an ADU for resale purposes.


If you have any questions about ADUs and guidelines for building, feel free to give us a call.


* Be aware that The City of Camas has a restriction that the main house needs to remain owner-occupied at least 6 months out of the year and at no time may the owner charge rent for the main living area. Plus, you may have to install a fire sprinkler system in the ADU.

This article was first published in News and Views at 

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ViewHomes™ grew out of our passion for nature, beautiful surroundings, and peaceful environments. Starting together in an urban environment, over the years we've gravitated towards areas with smaller populations and less density. We now enjoy our lifestyle in a rural environment, but with close proximity to metropolitan areas where we appreciate all the amenities of fine restaurants, shopping, and an easy drive to an international airport.
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Carol Williams
Although I'm retired, I love sharing my knowledge and learning from other real estate industry professionals. - Wenatchee, WA
Retired Agent / Broker / Property Manager

Congratulations! You're being Featured in the BananaTude Group.

Jan 26, 2020 01:26 PM #10
Debb Janes EcoBroker and Bernie Stea JD
ViewHomes of Clark County - Nature As Neighbors - Camas, WA
REALTORS® in Clark County, WA

Thank you kindly for the feature in BananaTude, Carol Williams, I appreciate you. 

Jan 26, 2020 01:30 PM #11
Grant Schneider
Performance Development Strategies - Armonk, NY
Your Coach Helping You Create Successful Outcomes

Good afternoon Debb Janes EcoBroker and Bernie Stea JD - I have not seen these were we live.  This is a great idea in areas with large size lots.

Jan 26, 2020 02:09 PM #12
Jeff Dowler, CRS
eXp Realty of California - Carlsbad, CA
The Southern California Relocation Dude

Great information here on ADUs for homeowners, and buyers who might be interested in adding one to a home they buy. We are certainly hearing more about them. I believe our requirement in Carlsbad is a maximum of 640 sf for a detached ADU, and no doubt the California Coastal Commission has other specific requirements in the areas they mandate near the beaches.


Jan 26, 2020 02:49 PM #13
Kathy Streib
Room Service Home Staging - Delray Beach, FL
Home Stager - Palm Beach County,FL -561-914-6224

Hi Debb and Bernie- I have been going back to the picture above and staring at it because I would love to have something like that for my family. Privacy and yet close enough to help if needed. 

Jan 26, 2020 06:29 PM #14
Endre Barath, Jr.
Berkshire Hathaway HomeServices - Beverly Hills, CA
Realtor - Los Angeles Home Sales 310.486.1002

ADU's are becoming very hot here in Los Angeles too, on a side note Happy Birthday Debb, hope it was a fun day, Endre

Jan 26, 2020 09:55 PM #15
Paul S. Henderson, REALTOR®, CRS
Fathom Realty Washington LLC - Tacoma, WA
South Puget Sound Washington Agent/Broker!

I come across inadequate septic design all the time and I find it odd because every thing else seems so well thought out...

Happy Monday to you both Debb Janes EcoBroker and Bernie Stea JD 

Jan 27, 2020 05:26 AM #16
Joan Cox
House to Home, Inc. - Denver Real Estate - 720-231-6373 - Denver, CO
Denver Real Estate - Selling One Home at a Time

Debb, this is necessary information to know with your specialty.  We still are not seeing many requests for ADUs.

Jan 27, 2020 07:29 AM #17
Debb Janes EcoBroker and Bernie Stea JD
ViewHomes of Clark County - Nature As Neighbors - Camas, WA
REALTORS® in Clark County, WA

Thanks all - we love helping people manage these issues whether buying or selling, or just needing some advice. We're always happy to help. 

Jan 28, 2020 06:11 AM #18
Patricia Feager, MBA, CRS, GRI,MRP
Selling Homes Changing Lives

Debb Janes EcoBroker and Bernie Stea JD - You provided excellent information about ADUs! As major cities across the United States continues to overpopulate and people are living longer, I believe this is just the beginning of a new way of life for many who have the land but don't have the income to buy larger multi-generational homes or can but there are not enough to choose from. I'm sure Planning and Zoning is very busy these days. I know P&Z in Flower Mound is extremely busy because many of the old farmland properties were grandfathered in until the passing of the owners; then zoning changed and in came lots of development. 

As you illustrated, there is a lot to consider from legalities to Health and Safety. In my areas outside Flower Mound limits, many homeowners of smaller homes converted garages to accommodate more living space, which created overcrowded street parking with limitations, depending on types of vehicles. As communities grow, we shall see many changes.

By the way, my guess is it will be just a short time before this one gets FEATURED! It would surely deserve it!

Jan 28, 2020 06:58 AM #19
Beth Atalay
Cam Realty and Property Management - Clermont, FL
Cam Realty of Clermont FL

This is excellent information on ADU's in your area Debb Janes EcoBroker and Bernie Stea JD. There's definitely a demand for them in my area but the zoning department makes it that much difficult. 

Jan 28, 2020 08:10 AM #20
Will Hamm
Hamm Homes - Aurora, CO
"Where There's a Will, There's a Way!"

Hello Debb and Bernie,  Great information to get the word out on ADU's for people that are interested.


Jan 29, 2020 09:46 AM #21
Roy Kelley
Realty Group Referrals - Gaithersburg, MD

This is important information to share with area residents. 

Jan 29, 2020 02:37 PM #22
Laura Cerrano
Feng Shui Manhattan Long Island - Locust Valley, NY
Certified Feng Shui Expert, Speaker & Researcher

The county is ready for something freshly ready a new beginning based on the vibe of your post here.

Jan 30, 2020 08:44 PM #23
Kat Palmiotti
406-270-3667,, Broker, Blackstone Realty Group - brokered by eXp Realty - Kalispell, MT
The House Kat

This is good information for anyone considering an ADU in Clark County, WA. I'm sure you will get some calls for more info!

Feb 01, 2020 05:26 AM #24
Lottie Kendall
Compass - San Francisco, CA
Helping make your real estate dreams a reality

ADUs are a growing trend in California also, Debb and Bernie. You've given Clark County WA residents some good, basic information about dos and don'ts; can and can't.

Feb 01, 2020 09:24 AM #25
Sharon Lee
Sharon Lee's Virtual Assistance - Jonesborough, TN
Retired and loving life

Great information for folks looking for this option.  I learned something new.  

Feb 01, 2020 01:34 PM #26
Debb Janes EcoBroker and Bernie Stea JD
ViewHomes of Clark County - Nature As Neighbors - Camas, WA
REALTORS® in Clark County, WA

Thanks guys. Guessing you found it today through Carol Williams, Second Chance Saturday series. :) 

Feb 01, 2020 01:40 PM #27
Debe Maxwell, CRS | The Maxwell House Group | RE/MAX Executive | (704) 491-3310 - Charlotte, NC
The right Charlotte REALTOR!

Love this information and of course, you know this is one of my favorite subjects, Debb! I went on vacation last summer with friends and we have devised a plan to have a large piece of land with 6 ADUs for the 6 friends and their spouses to retire to - of course on the lake! The rules on the lake are not at strict as they are in the city.

Which reminds me - "In rural properties, separate ADU structures are simply not allowed." seems reversed to me!

Feb 06, 2020 07:09 PM #28
Caroline Gerardo
Pinnacle Home Loans - Newport Beach, CA
C. G. Barbeau the Loan Lady nmls 324982

Excellent post about ADU's I'm seeing many people finance these and it's exciting to see all the many solutions

Feb 24, 2020 05:10 PM #29
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REALTORS® in Clark County, WA
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