ADU construction in Issaquah
ADU Construction in Issaquah, WA
Backyard cottages, basement and garage conversions, and hillside DADUs, built for Issaquah lots where slope and critical areas decide what fits. Local pricing, permits through the City of Issaquah Permit Center, and an honest number before we build.
The promise
An Issaquah ADU that starts with whether your lot can carry one
On Issaquah lots, feasibility is the whole game, and it is where we start. You get a straight read on what your lot allows, an ADU built to the standard of a real home, a number that accounts for the ground it sits on, and one licensed team from feasibility to final inspection.
Why choose us
Why choose us for your Issaquah ADU
01
Feasibility first, and it matters more here
In Issaquah, whether a lot can carry an ADU is a real question, not a formality. Slope, critical areas, setbacks, and design review can all decide it. We run feasibility before you spend a dollar on design, and if the lot will not work, we tell you straight away.
02
An honest number, before we build
ADU budgets get blindsided by site work, utilities, and, on the foothills, foundations and retaining. We scope the whole thing, including the ground it sits on, and lock the price before we start.
03
Built as a home, not an outbuilding
An ADU you will rent or move a parent into has to be warm, dry, and quiet. We build it to the same standard as the main house, from insulation and windows to finishes, so it lives like a real home.
04
We carry the Issaquah permit
An ADU has its own permit and plan review through the City of Issaquah Permit Center, usually a pre-construction meeting, and often critical-area or geotechnical review. We assemble it, file it, and see it through inspection.
Cost
What an ADU costs in Issaquah
An ADU price depends on type, site, and utilities, and the ground under it matters more in Issaquah than most places. Here are the three levels, each quoted to your lot rather than an Issaquah average.
Level 01
Conversion (AADU)
Turn a basement or garage into a legal attached unit.
- Convert existing space
- Add a kitchen and bath
- Egress, insulation, and systems
Your price: quoted to your lot and site, before we build.
Level 02
Detached ADU (DADU)
A new backyard cottage on a workable lot.
- New foundation and structure
- Full kitchen and bath
- Utilities run to the unit
Your price: quoted to your lot and site, before we build.
Level 03
Hillside or custom DADU
An engineered unit for a sloped or constrained lot.
- Engineered or daylight foundation
- Retaining and drainage
- Higher-end or two-story build
Your price: quoted to your lot and site, before we build.
Every level is quoted to your lot and site, before we build. The ADU construction guide walks through what moves the number.
Permits
ADU permits in Issaquah
An ADU carries its own permit path, and Issaquah lots often add reviews on top. Here is how it runs.
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An ADU has its own permit path
An ADU goes through its own plan review, usually starting with a pre-construction meeting in Issaquah. We map the full scope, including any special reviews your lot triggers, before design.
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Critical-area and geotechnical review
On creek-side or sloped lots, the permit can require critical-area review and a geotechnical report. We line those up early so they do not stall the build later.
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Filed with the Issaquah Permit Center
The package runs through the City of Issaquah Permit Center, part of Community Planning and Development. We prepare it and carry it through review and every inspection.
Local lots
What Issaquah lots mean for your ADU
More than any other project, an ADU lives or dies on the lot. These are the Issaquah realities we assess first.
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Steep slopes and the Issaquah Alps
Many Issaquah lots rise or drop sharply toward Squak, Cougar, or Tiger Mountain. A DADU on a slope needs an engineered foundation, retaining, and often a daylight or downhill design. We read the grade before anything is drawn.
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Critical areas and Issaquah Creek
Salmon-bearing streams, wetlands, floodplain, and landslide-hazard ground place buffers and review on many lots, which shape where a DADU can sit or whether it fits at all. We check for them at the start, not after design.
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Washington ADU rules, Issaquah limits
State law has widened where ADUs are allowed, and Issaquah applies its own size, height, and parking rules within that. We confirm the current rules for your specific lot before you invest in a design.
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Highlands lots and design review
In master-planned areas like the Highlands and Talus, smaller lots and design standards shape what fits, and a basement or attached ADU is often the better route than a detached one. We design to the community rules so it gets approved.
FAQ
Issaquah ADU construction FAQs
Can I build an ADU on my Issaquah lot?
Maybe, and it is worth checking before you design. Washington has widened where ADUs are allowed, so more lots qualify than before, but in Issaquah slope, critical areas, setbacks, and design review can still decide it. We run feasibility on your specific lot first.
What is the difference between an attached ADU and a DADU?
An attached ADU (AADU) lives within or against your house, usually a basement or garage conversion. A detached ADU (DADU) is a separate structure, typically a backyard cottage. They permit, cost, and sit on the lot differently, and on tight or sloped Issaquah lots one is often far more practical than the other.
Can you build a DADU on a steep or hillside lot?
Yes, and it is common here. A sloped lot needs an engineered foundation, retaining, and careful drainage, often with a daylight or stepped design that uses the grade. We bring in the geotechnical and structural work and build from stamped plans.
What if my lot has Issaquah Creek or critical areas?
Those features add buffers and review that can limit where a DADU sits, or rule one out. It does not automatically stop the project, but it has to be sorted before design. We check for streams, wetlands, floodplain, and slope hazard at the very start.
Can I rent it out, and do I have to live on-site?
Usually you can rent it, and owner-occupancy rules have relaxed across much of Washington, though the details vary and can change. We confirm the current Issaquah rules for renting and occupancy for your address before you commit.
How much does an ADU cost in Issaquah, and how long does it take?
It depends on type, size, the site, and utility connections, and a hillside DADU costs more than a garage conversion. We price against your real lot conditions rather than an average, and put a schedule in writing. Permits, geotechnical review, and site work are usually the biggest timeline drivers.
Ready when you are
Get a free Issaquah ADU estimate
Tell us about your lot and we will call within one business day, check the feasibility, and put a written estimate together with no pressure to sign.