Question 1

How long does a detached ADU take from kickoff to keys?

Accepted Answer

Plan on 8–12 months end-to-end: 6–10 weeks for design and engineering, 12–20 weeks in permit review, and 16–24 weeks of active construction. Schedules tighten when the lot is flat, the design uses a pre-approved plan, and utility upgrades are minimal.

Question 2

How fast can a garage conversion (AADU) finish?

Accepted Answer

Garage conversions and attached ADUs typically deliver in 3–5 months: 4–6 weeks of design, 8–12 weeks of permitting, and 8–14 weeks of construction. The existing slab and walls usually shave 30–40% off both the schedule and the budget compared to a new DADU.

Question 3

How long is permit review in Seattle, Bellevue, Kirkland, and Tacoma?

Accepted Answer

As of this quarter: Seattle SDCI averages 12–16 weeks, Bellevue 8–12 weeks, Kirkland 6–10 weeks, and Tacoma 8–14 weeks. Pre-approved DADU plans cut Seattle review to 4–6 weeks. We track jurisdiction velocity weekly and quote permit windows from current data, not last year's averages.

Question 4

What can delay an ADU project, and how do you defend against it?

Accepted Answer

The three usual culprits are city correction cycles, side-sewer capacity surprises, and long-lead specialty items (windows, panels, custom millwork). We mitigate by pre-checking sewer capacity at design, ordering long-lead items at permit submittal, and assigning a permit expediter to every project.

Question 5

Do you build through Pacific Northwest winters?

Accepted Answer

Yes. Foundations are sequenced for the drier shoulder seasons when possible, but framing and finish work continue year-round under temporary weather protection. Our schedules include a documented weather contingency (typically 10–15 working days) so winter rain doesn't push your handover.

Question 6

What does a detached ADU actually cost in 2026?

Accepted Answer

Most of our turn-key DADUs land between $200,000 and $400,000, or roughly $330–$380 per square foot all-in (design, permits, site work, build, and warranty). A 1,000 sqft DADU pencils to $330K–$380K. The spread is driven by size, finish tier, and how much the lot fights you — slope, trees, and utility distance are the big movers.

Question 7

What does an attached ADU (AADU) or basement conversion cost?

Accepted Answer

AADUs and basement conversions typically run $170,000–$280,000. They benefit from shared walls, existing utilities, and a smaller permit scope, but ceiling height, egress windows, and separate-entry framing can quietly add $20K–$40K if the existing house wasn't designed for it.

Question 8

What does a garage conversion cost?

Accepted Answer

Garage conversions usually fall between $120,000 and $200,000 depending on whether the slab needs to come up, the roof needs structural reinforcement, and how far the kitchen/bath plumbing runs to the existing main line. The single biggest variable is insulation upgrades — most older garages need full envelope work to meet code.

Question 9

What's the price per square foot — and why is that number misleading?

Accepted Answer

Our DADUs pencil to roughly $330–$380/sqft all-in, with a $330/sqft floor on 1,000+ sqft builds. Smaller ADUs land a bit higher because kitchens, baths, and utility hookups don't scale down. The number is useful for sanity checks, but always compare total project cost against scope, not /sqft against /sqft.

Question 10

What hidden costs blow up an ADU budget?

Accepted Answer

The five we see most: side-sewer upgrades ($8K–$25K), electrical service panel upsize ($4K–$12K), tree-protection or removal permits ($2K–$15K), stormwater retention ($5K–$20K), and arborist or geotech reports ($2K–$6K). Every Golden proposal includes a site-conditions allowance so these show up as line items, not surprise change orders.

Question 11

Do you bid fixed-price or time-and-materials?

Accepted Answer

Every contract is a fixed-price agreement signed after design and engineering are complete. We don't bid T&M for ADUs because the scope is knowable — anyone who insists on T&M is asking you to absorb their risk. The only variable line items are owner-selected allowances (appliances, plumbing fixtures, flooring) that you control.

Question 12

How accurate is your free consultation budget range?

Accepted Answer

Our consult-stage range is typically ±15% of the eventual fixed-price contract. We tighten that to ±3% during schematic design after the survey and geotech are in. If a competitor is offering ±0% before you've paid for engineering, they're either padding the number or about to write change orders.

Question 13

How do most clients pay for an ADU?

Accepted Answer

Roughly 55% use a HELOC or cash-out refi against existing home equity, 30% use a renovation construction loan (Fannie HomeStyle, FHA 203k, or a local credit union ADU product), and 15% pay cash. We don't lend, but we make warm intros to four Puget Sound lenders who actually understand ADU draws.

Question 14

What's an ADU construction loan and when does it make sense?

Accepted Answer

It's a single-close loan that funds construction in draws and converts to a permanent mortgage at handover, underwritten on the post-construction appraised value of your property (house + ADU). It makes sense when you don't have enough existing equity to cover the build but the finished-value math pencils — common for newer purchases.

Question 15

Will an ADU appraise for what it costs to build?

Accepted Answer

In most King and Pierce County neighborhoods, a well-built DADU appraises for 80–110% of build cost — better when there are recent comparable ADU sales nearby. The 'appraisal gap' is real but shrinking fast as ADU comps accumulate; we share recent appraisal data for your zip during the consult.

Question 16

Are there grants, rebates, or tax incentives for building an ADU?

Accepted Answer

Seattle's pre-approved DADU program waives ~$3K in plan-review fees. Puget Sound Energy and Seattle City Light offer heat-pump and induction rebates ($500–$2,500). Washington has no state income tax, but ADU rental income is federal-taxable; bonus depreciation on the structure can shelter much of it — talk to a CPA.

Question 17

Do you have in-house architects or use outside firms?

Accepted Answer

Architecture, interior design, and structural engineering are in-house. MEP (mechanical, electrical, plumbing) and civil are long-term partners we've worked with for 8+ years. One contract, one accountable schedule, no finger-pointing when something needs to change.

Question 18

How many design revisions are included?

Accepted Answer

Three rounds of schematic revisions are baked into the design fee, which is enough for 95% of projects. We deliberately front-load the first round with three distinct floor-plan options so you're choosing between real alternatives, not nudging a single plan around.

Question 19

Can you match the architecture of my existing house?

Accepted Answer

Yes — we routinely match Craftsman, mid-century, Tudor, and contemporary primary homes. Roof pitch, eave depth, window proportions, siding rhythm, and trim profiles are documented from your house at the site visit and carried into the ADU drawing set so the result reads as one property, not two.

Question 20

Can the ADU be designed for aging-in-place or accessibility?

Accepted Answer

Yes, and we recommend it for primary-home owners over 55. Standard accessible upgrades — 36" doors, zero-step entry, blocking for future grab bars, roll-in shower, accessible kitchen heights — add $8K–$18K to a DADU and keep the unit useful for the next 40 years.

Question 21

Should I use a pre-approved plan or design from scratch?

Accepted Answer

Seattle's pre-approved DADU plans save 4–8 weeks of permitting and ~$15K–$25K in design fees, but they're sized and styled for typical lots. Custom design wins when the lot is unusual (sloped, narrow, view-driven) or when you want the ADU to match a specific architectural language. We build both.

Question 22

Who pulls the permits — me or you?

Accepted Answer

We do, every time. Golden acts as the permit applicant, manages all city corrections, schedules inspections, and closes the permit at final. You'll see every submission and correction in your project portal, but you never wait in line at SDCI.

Question 23

How does Seattle's SDCI ADU permit process actually work?

Accepted Answer

Two parallel tracks: a building permit (structural, envelope, energy) and a side-sewer/water permit. SDCI typically issues a first correction round at week 6–8, a second at week 11–13, and approval at week 14–16. Pre-approved plans skip the first review entirely.

Question 24

How is Bellevue different from Seattle for ADU permits?

Accepted Answer

Bellevue review is faster (8–12 weeks) but stricter on tree retention, impervious-surface limits, and design review for ADUs over 800 sqft. Setback rules are also more conservative on R-1 lots. We pre-flight every Bellevue submittal against the current bulletin set.

Question 25

What about Kirkland, Redmond, and Tacoma?

Accepted Answer

Kirkland (6–10 weeks) and Redmond (8–12 weeks) both allow DADUs by right in most residential zones with relatively predictable review. Tacoma (8–14 weeks) is the friendliest for AADUs and basement conversions thanks to recent zoning reform. Each city has its own quirks — we maintain an internal cheat-sheet per jurisdiction.

Question 26

Do I need a land-use or design review before the building permit?

Accepted Answer

For most single-family ADUs in Seattle, Bellevue, and Kirkland: no. Design review kicks in for ADUs in landmark districts, environmentally critical areas (steep slope, wetland, liquefaction), or shoreline jurisdiction. We screen for all three on day one of the consult.

Question 27

What's the minimum lot size for a DADU?

Accepted Answer

Seattle removed minimum lot-size requirements for DADUs in 2019 — if you have a single-family lot, you almost certainly qualify. Bellevue requires 5,000 sqft, Kirkland 7,200 sqft (with exceptions), and Tacoma 5,000 sqft. We confirm your lot's eligibility for free during the consult.

Question 28

What are the setback and height rules?

Accepted Answer

Seattle: 5 ft side/rear setbacks, 18 ft height (23 ft with pitched roof). Bellevue: 5 ft sides, 10 ft rear, 24 ft height. Kirkland: 5/10/25. These shrink your buildable footprint more than people expect — we plot the buildable envelope on day one before drawing anything.

Question 29

How much square footage am I allowed to build?

Accepted Answer

Seattle allows DADUs up to 1,000 sqft (1,200 sqft with a green-building bonus). Bellevue caps at 1,000 sqft. Kirkland at 800–1,200 sqft depending on lot size. The cap and the lot's FAR (floor-area ratio) interact — large existing houses on small lots sometimes hit FAR before they hit the ADU cap.

Question 30

Does Seattle's tree code affect where I can build?

Accepted Answer

Yes, and it's the single most common surprise. Trees ≥6" diameter in single-family zones are protected; building within their critical root zone requires an arborist report and may require relocation of the ADU. We run a tree-survey overlay before schematic design so you never invest in a plan the trees won't allow.

Question 31

What if my side sewer or electrical service isn't big enough?

Accepted Answer

Side-sewer capacity is checked against existing fixture count plus ADU fixture count; if you're over, a sewer-cap calc or full sewer replacement is required ($8K–$25K). Electrical: most ADUs need a 100A or 200A subpanel; if the main service is 100A you'll likely upsize ($4K–$12K). We diagnose both at the site visit.

Question 32

Can I rent out the ADU long-term?

Accepted Answer

Yes — long-term rentals (30+ day leases) are allowed in every city we build in. Seattle, Bellevue, Kirkland, and Tacoma all require a basic rental registration ($55–$175/year) and a periodic inspection (every 5–10 years depending on city).

Question 33

Can I run it as a short-term rental (Airbnb)?

Accepted Answer

Rules vary sharply by city. Seattle: yes, with a short-term rental license and operator's license — owner doesn't need to live on site, but the unit must be one of only two STR licenses per operator. Bellevue and Kirkland: only with owner-occupancy of either the primary house or the ADU. Tacoma is the most permissive. Always verify current code before counting on STR income.

Question 34

Should the ADU have separate utility meters?

Accepted Answer

For long-term rentals: usually yes for electric ($3K–$5K), optional for water and gas. For STR or family use: a single meter with sub-billing software ($400–$800) is usually cheaper. Separate meters increase appraised value modestly and simplify future sale or condo-conversion.

Question 35

Do I have to live on the property to build an ADU?

Accepted Answer

No. Seattle removed owner-occupancy requirements in 2019. Bellevue, Kirkland, and Tacoma also allow non-owner-occupied ADUs, though some cities require it if you want a short-term rental permit (see above). This means ADUs are a legitimate investment-property play, not just a backyard cottage for relatives.

Question 36

How disruptive is construction to my daily life?

Accepted Answer

Plan on 16–24 weeks of weekday site activity (7am–5pm), peak noise during demo, foundation, and framing (~4 weeks total). We provide a job-site contact, weekly written progress reports, and a single point of escalation. Driveway access is preserved except for 1–2 short closures we schedule with you in advance.

Question 37

Will my utilities (water, power, internet) be interrupted?

Accepted Answer

Brief planned shutoffs only: typically one 4–6 hour water shutoff for the side-sewer tie-in, and one 2–4 hour power interruption when the meter is upgraded or the subpanel is energized. Internet is never affected. All shutoffs are scheduled with you at least 5 business days ahead.

Question 38

What happens to parking and street access during the build?

Accepted Answer

We secure a city right-of-way permit when a dumpster, port-a-john, or storage container needs the curb. Crew vehicles park off-site when possible. On tight urban lots we coordinate with neighbors before mobilization and provide a written disruption schedule — most complaints come from surprises, not the work itself.

Question 39

Do you notify the neighbors?

Accepted Answer

Yes. We hand-deliver a project intro letter to immediate neighbors before mobilization with the schedule, our site supervisor's direct line, and the city permit number. Cities like Seattle also post a public notice of construction — we handle that filing as part of the permit package.

Question 40

What warranty do I get on the finished ADU?

Accepted Answer

1-year comprehensive workmanship warranty on everything we built and installed, 2 years on mechanical/electrical/plumbing systems, and 10 years on the structural envelope (foundation, framing, roof). Manufacturer warranties on appliances, windows, and roofing pass through to you directly.

Question 41

Are you licensed, bonded, and insured?

Accepted Answer

Yes — active Washington general contractor license GOLDESA747LZ (verifiable at lni.wa.gov), $25,000 contractor bond, $2M general liability, and full workers' comp coverage on every employee and subcontractor. Certificates of insurance are sent to you and your lender before mobilization.

Question 42

How do change orders work?

Accepted Answer

Any scope change goes through a written change order with a fixed price and schedule impact before any work happens — no exceptions. About 70% of our projects close with zero owner-initiated change orders. The remaining 30% usually add owner upgrades (better appliances, an extra skylight) rather than fix surprises.

Question 43

What happens during the free consultation?

Accepted Answer

A 45-minute on-site or video walkthrough. We review your zoning, plot a buildable envelope, identify any tree/sewer/setback constraints, and give you a written budget range and timeline within 48 hours. No deposit, no obligation, no upselling.

Question 44

What's the payment schedule once we sign?

Accepted Answer

Standard schedule: 10% at design kickoff, 15% at permit submittal, 20% at foundation, 20% at framing dry-in, 20% at drywall, 10% at substantial completion, 5% at final/punch-list closeout. Construction-loan draws are billed on the same milestones.

Question 45

How do I know my project is on schedule and on budget?

Accepted Answer

Every client gets access to a project portal with the live schedule, weekly photo logs, every permit submission and correction, every signed change order, and a real-time budget tracker. The same data is summarized in a Monday morning email so you don't have to log in to know where things stand.

Build type	Typical sqft	SeaTac all-in	Build time	Deep dive
DETACHED ADU in SeaTac	400–1,000 sqft	$123K–$352K	6–8 months	SeaTac cost data →
ATTACHED ADU in SeaTac	300–800 sqft	$84K–$282K	4–5 months	SeaTac cost data →
GARAGE CONV. in SeaTac	200–600 sqft	$57K–$211K	3–4 months	SeaTac cost data →
MODERN ADDITIONS in SeaTac	Custom	$106K–$422K	Project dependent	SeaTac cost data →
GENERAL CONTRACTING in SeaTac	Any	Custom	Project dependent	SeaTac cost data →
FEASIBILITY STUDIES in SeaTac	—	$1,500 – $3,500	1–2 weeks	SeaTac cost data →

City	Permit window	Min lot	800 sqft DADU	Cost index
SeaTac (this page)	8–12 wk	7,200 sqft	$410k–$505k	0.88×
Tukwila ADU FAQ	8–12 wk	7,200 sqft	$405k–$500k	0.87×
Burien ADU FAQ	8–12 wk	5,000 sqft (ADU lots)	$420k–$520k	0.90×
Des Moines ADU FAQ	10–14 wk	7,200 sqft	$420k–$525k	0.91×
Renton ADU FAQ	10–14 wk	5,000 sqft	$430k–$535k	0.93×
Kent ADU FAQ	8–12 wk	5,000 sqft	$410k–$505k	0.88×
Federal Way ADU FAQ	10–14 wk	7,200 sqft	$410k–$505k	0.88×

SeaTac ADU FAQ

Building an ADU in SeaTac — answered

How loud is it really to live in a SeaTac ADU?

What does the sound-attenuation premium cost?

Is owner-occupancy required?

What does an 800 sqft DADU cost in SeaTac, WA?

How long does the SeaTac permit process actually take?

What zoning rules apply to ADUs in SeaTac?

Can I rent the ADU in SeaTac as short-term (Airbnb)?

What rent can I expect from a new ADU in SeaTac?

Do I need a separate utility meter for the ADU in SeaTac?

What incentives or fee waivers are available in SeaTac?

Which SeaTac neighborhoods do you build in most?

ADU types we build in SeaTac

Frequently asked, by service type

How big can a detached ADU (DADU) be in Seattle?

Can I convert my Seattle basement into an attached ADU (AADU)?

Can my detached garage be legally converted to a rental in Seattle?

Do I need a permit for a home addition in Seattle?

Are you a licensed general contractor in Washington State?

What does a feasibility study actually include?

Go deeper on SeaTac

SeaTac ADU cost by build type

SeaTac vs. nearby cities — at a glance

Question we didn't answer?

More SeaTac ADU answers and resources

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