What is going on with AADU’s and DADU’s ?
AADU (attached accessory dwelling units)
DADU (detached accessory dwelling units)
The city has established new zoning codes for backyard cottages and mother in law units. Seattle Municipal Code 23.44.041, to be fully adopted and implemented on August 8th, 2019. Below is a breakdown of the new code. Scroll down to see an example site plan with the new codes applied.
Minimum Residential Lot Size : 3,200 sf
Maximum Floor Area DADU & AADU : 1,000 sf (this does not include stairs, garages, utility closets and other support spaces)
Maximum Units per residential lot : Either (2) total AADU’s
or (1) AADU & (1) DADU
Maximum Lot Coverage : 5000 sf or bigger 35% of total lot
less than 5000 sf 15% of lot plus 1,000 sf
Maximum Height : Varies based on lot width, as well as combination of space types. A DADU 18-23 feet
Parking Requirements : None
Owner Occupancy Requirements : Owner must live in a newly created unit for one year. Then no requirements for owner occupation.
Primary Residence Area Limitation : A new limit will be imposed of a maximum of 2,500 sf
Rear Yard Coverage : 60 percent of a rear yard can be covered by a DADU and other accessory structures, if the DADU is 15 feet or less in height. Rear
yard coverage for structures other than a DADU cannot exceed 40 percent.
ADU primary entry door : any side, so long as it is more than 10’ from property lines
BACKYARD COTTAGE FAQ’s
What is an ADU? And a DADU? Backyard Cottage? What about AADU?
An ADU (accessory dwelling unit) is a stand-alone single family unit, which includes all the code obligated amenities and features of a house such as proper structure, egress, light, ventilation, water, electricity, heating, kitchen, bathroom, parking etc.
There are two distinct building code elements that make a structure an ADU, a kitchen sink and a stove. These two items are not allowed in structures like an art studio or guest room or other accessory buildings. There are two types of ADUs - detached and attached. A DADU, also known as a Backyard Cottage, is a single family dwelling unit that is not attached to the primary dwelling unit (the main house). An AADU is attached, sharing a wall or some other connection to the main house.
How much does it cost?
A full design package is typically 12-18% of total construction costs, 6-9% to get a permit. Our recent projects have been around $425-$575 a square foot. This includes all construction costs, including site work, utilities and all finishes - everything you’d expect in a finished residential project, excluding landscaping.
Example:
800 sf new backyard cottage
(800sf) x (500$/sf) = $400,000
(12%) x (400,000) = $48,000 full design
(6%) x (400,000) = $24,000 permit
How long does it take?
A typical project can take approximately a year for design and build, depending on the start time - there can be limitations for excavation and digging placed on certain projects (no work) during the winter months. Broadly speaking, you can expect 2-4 months for design, 3-6 months for the city to review, and 4-8 months to build.
Can I get financing for this?
Of course! There are many ways to finance a backyard cottage. In order to get a construction loan you will need permitted drawings and a signed construction bid from a licensed contractor. Please see the handouts available from Washington Federal just down the street. Homestreet Bank has great products, too. We have other resources as well, please just ask. Or your great-uncle :)
What is the ROI, how long?
This is dependent of course on the specifics of the project, but also how the project is understood between the client and their checkbook! Analyzing ROI according to next year’s resale value or Specific target rental income is very different than the value of a new view, or drinking your morning coffee in a kitchen you absolutely love. Investing in quality of life can be difficult to put a number on. See also the appendix for a graph that shows ROI’s for backyard cottages. The current Seattle market rents smaller spaces for about 20-30k annually, if you use this number you can project a 10-15 year return.
What is the design cost?
Costs typically range anywhere from 6% to 18% of construction costs. Usually, to simplify this math, we like to discuss residential projects in terms of out-of-pocket costs, i.e. project costs, the numbers you write on the check. These costs include design, construction, and sales tax. We’ve shared a graphic that can help frame this all visually.
How do you calculate the design cost? By time or size or other?
Design costs are typically 12-18% of construction costs, but is always billed hourly. Costs are dependent on the client’s interests, decision-making and the complexity of permitting.
Is there a cost range depending on size and finishes?
It is more expensive to build small - the cost of deploying and setting up a construction project will be proportionately higher for a small project. Finishes will have a large impact in wet spaces, i.e. bathroom and kitchen. We have costs-per-square-foot that cover all of these areas to help analyse how the project programming comes together.
What are barebones cost per foot?
$350 per square foot will get you very basic construction. Seattle is expensive! Building a backyard cottage in North Dakota would be substantially cheaper :) This is something we all are working on together, but the realities of our industry and city are real and can be addressed and mitigated with professional help, a good attitude and a bit of discipline.
Can I mitigate the construction cost by contributing my labor? Or other elements?
Yes, you can limit costs by putting in your own blood sweat and tears, however this is not generally recommended. Unless you’ve had some experience, this will be the first time you are doing it, so there will likely be errors, errors that could very easily accrue heavy costs. There is always the option of utilizing a General Contractor for intermittent guidance, to mitigate those risks, but the tried and true method for a successful project is partnering with experienced professionals who will guide and protect your interests throughout the process.
Is the site work cost in addition to the cost of the build?
No, we budget for site work in our estimates, but the cost impact does depend on the scope of the project and the site significantly. if you have an existing structure there will likely be limited site work. If you have a complex site and a complex scope, there may be expensive foundation, utilities or other requirements.
What can make this process more or less expensive?
Not knowing what you want is a biggie. We want to find the best fit for what the project demands, and we have a lot of experience knowing what is likely going to work best. We do find frequently that suggestions we make during design are taken up finally only once construction has begun. Design provides the most cost-effective means for exploring options. Making changes during construction is expensive and can have unanticipated consequences. Having unrealistic expectations (schedule, budget, scope) can also be problematic. Other more tangible issues can be access to site, or other limitations due to challenging sites on steep slopes or in other environmentally critical areas (wetlands, shorelines, etc).
What is the single thing I can do to keep costs down? keep timeline to a minimum?
As the client, know what you want, make clear decisions and allow the building
professionals you partner with to help guide you.
Is there any City documentation available on ADU’s?
Yes:
http://www.seattle.gov/Documents/Departments/Council/ADU_DEIS_Public_Hearing_boards.pdf
What is the minimum size allowable for an ADU?
There is no specific minimum size, however there are minimums for a bedroom space
which is 70 sf, a minimum for a bathroom is 45 square feet and a minimum for a kitchenette would be about 25 sf. We have designed a backyard cottage that is just 288sf.
Will the city change the building codes soon?
Yes, but the timing is uncertain. The city will be pushing for the adoption of the new codes, the amount of time that it takes is somewhat unknown, but they are more towards the end of the process.
Is there a minimum lot size for an ADU?
Currently 4,000 sf
Potentially 3,200 sf
Is there a maximum size for an ADU?
Currently 800 sf - total, including storage and uninhabitable spaces.
Potentially 1,000 sf - not including garage, storage, etc.
Are there height restrictions?
Currently 15-23 feet, depending on lot width and size.
Potentially 1-3 feet taller than existing limitations.
If I can’t build a DADU because my lot is too small, can I make an AADU?
Yes.
Where can I put a DADU?
Only in the backyard.
Do you have a standard design that fits any lot?
We have designed a version that would fit many if not most lots in Seattle, yes, but the reality is that real projects require attention and site work specific to the exact lot conditions. Even if you buy a prefabricated unit and it drops in on a helicopter drone, you will have to go through the same permit and build process with the city as a custom build, and all site-work (footings, utilities, etc.) will be in response to the challenges of your lot in particular. No one’s figured out how to build a prefabricated sewer pipe just yet.
How can I rent out an ADU?
Most likely you can rent in anyway you want to, daily, weekly, monthly etc. The caveat is at this point you would have to occupy the main residence for at least 6 months of the year (this could change with the new codes in which there is no owner occupancy requirement).
Does it have to be inspected and registered by the City before I can rent it out?
Yes - there is a simple form and small fee. Always check city regulations as well as insurance requirements.