ADU & DADU guides.
Real numbers, permitting know-how and honest advice on building backyard homes across Seattle, King and Snohomish County — written by the crew that builds them.
ADU & DADU Guides
28 guidesADU Building in Sammamish, WA
How DIGS Construction plans, permits and builds backyard cottages and detached ADUs on Sammamish, WA lots, from the first site visit to the keys.
Read the guideADU Cost Breakdown in Seattle: Where Every Dollar Goes (2026)
Where the money actually goes on a Seattle ADU, line by line: design, SDCI permits, side sewer work, foundation, finishes, and the site costs national guides skip.
Read the guideGarage to ADU Conversion in Seattle: What It Really Takes
How we decide whether a Seattle garage can be converted into a legal ADU or should be rebuilt on the same spot, and what drives cost and timeline.
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Building a DADU in North Seattle: Northgate, Lake City and Maple Leaf
North Seattle is where a lot of our work happens: wide mid-century lots, light rail at Northgate, and a creek system that decides where some cottages can go. Here is what is different about building here.
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Tiny House vs. ADU in Washington: What You Can Actually Put in Your Backyard
Washington recognized tiny houses in law, but a unit on wheels is still an RV to the building code. Here is where the line falls between a tiny house, a tiny house on a foundation, and a DADU.
Read the guideUsing an ADU as a Home Office: Shed, Studio or a Real Backyard Home?
“ADU home office” is a breakout search in Washington this fall. Here is the honest comparison — office shed, detached studio or a permitted DADU — and why the third one is the only one that stays flexible.
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DADU Homes in Seattle: Five Real Backyard Homes, and What Each One Shows
Renderings are easy. These are five DADU homes we built and photographed at handover — what each lot allowed, how the plan responded, and the detail worth copying from every one.
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What Does an ADU General Contractor Actually Do?
People picture a GC as the person who swings the hammer. On a backyard ADU the hammer is the small part — the job is permits, sequencing, inspections, the schedule and carrying the risk.
Read the guideInside the Classic Cottage: A 1,000 sq ft DADU, Room by Room
Our signature cottage, documented at handover: covered porch, main-floor living, two bedrooms up, two-tone Hardie siding under a dark metal shed roof. A real build, not a rendering.
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Design-Build vs. Architect + Contractor: Which Way to Build an ADU?
One contract or two? Design-build is faster and prices earlier; hiring an architect separately buys you an independent advocate. Here is the honest case for each.
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ADU Rules on the Eastside: Bellevue, Kirkland and Redmond
Three cities, three different answers. Bellevue only began allowing detached ADUs in July 2025, Kirkland has allowed two since 2020, and Redmond has rewritten its rules twice in eighteen months.
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Designing an ADU for Aging in Place
Most accessibility costs almost nothing at framing and a fortune afterwards. The decisions worth making while the walls are still open.
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Heating and Cooling an ADU: What Actually Works
A small, well-sealed building has very different heating needs from a house — and Washington’s energy code has largely settled the question of what goes in it.
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Two ADUs or a Fourplex? What You Can Build on a Seattle Lot
One unit per 1,250 sq ft, plus three exceptions — and two of your units may be ADUs. The limit is rarely the unit count; it is footprint, floor area and trees.
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What Are the Downsides of an ADU?
Most ADU pages only sell the upside. Here are the honest drawbacks from a builder who has completed 100+ of them — and who each one actually rules out.
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Drainage, Excavation and Site Work on a Backyard DADU
The cottage is the predictable part. Where the water goes, what the soil holds and how equipment reaches the back yard is where a DADU budget actually moves — and Seattle rewrote the stormwater rules in 2026.
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ADU Plans in Washington: Pre-Designed vs. Custom
Downloadable ADU plans are cheap and permit sets are not, and the gap between the two surprises most homeowners. What a permit-ready plan set actually contains, and when a stock plan works.
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ADU vs. Home Addition: Which Is Right for You?
Add on to your house or build a separate ADU? Here’s how the two compare on cost, added value, rental income and privacy — so you pick the right one for your goals.
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Can You Convert a Basement into an ADU in Seattle?
A basement conversion can be a lower-cost path to an ADU — if the basement suits it. Here’s what it takes (egress, height, moisture, permits) and how it compares to a DADU.
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Prefabricated ADU vs. Custom-Built: Which Should You Build in Seattle?
Prefabricated ADUs promise fast and cheap; custom builds offer fit and quality. The honest comparison — all-in cost, crane access, site work and timeline — on a real Seattle lot.
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Backyard ADU Design Ideas for Seattle Homeowners
A great DADU feels bigger than its footprint. Design ideas for backyard ADUs that get light, storage, flow and privacy right — so a small home lives large.
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ADU Floor Plans: How to Choose the Right Size and Layout
The right ADU floor plan balances your lot, budget and how you’ll use the space. Here’s how to choose a size and layout that works — for rent or for family.
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Multigenerational Living: How Families Use an ADU
A backyard ADU keeps family close without giving up independence — for aging parents, adult kids, or a caregiver. How multigenerational living works with a DADU.
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Garage Conversion vs. Detached ADU: Which Should You Build?
Convert the garage or build a detached DADU? Here’s how the two paths compare on cost, privacy, rental value and construction — and how to pick the right one.
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How to Choose an ADU Contractor in Seattle
“ADU contractor near me” is one of the fastest-rising searches in Washington. Here’s how to vet an ADU builder — licensing, honest pricing, and the exact questions to ask.
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What Is an ADU in Real Estate?
ADU stands for Accessory Dwelling Unit — a legal second home on your lot. Here’s what that means for your property’s value, rental income and resale in the Seattle area.
Read the guideADU vs DADU: What’s the Difference?
An ADU is any second dwelling on your lot; a DADU is the detached, standalone version. Here’s how the two compare on cost, privacy, construction and permitting.
Read the guideHow Much Does It Cost to Build a DADU in Seattle?
Real 2026 price ranges for a backyard DADU in the Greater Seattle area — and the three cost categories that decide your final number.
Read the guideCustom Homes
7 guidesEnergy-Efficient Home Building in Seattle: What to Know
A well-built home costs less to run for decades. Here’s what actually makes a new home or ADU energy-efficient in the Seattle area — and why it pays back every month.
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How to Finance a Custom Home in Seattle
Building a home is financed differently than buying one. A plain-English guide to construction loans, lot loans and construction-to-permanent financing in the Seattle area.
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How Much Does It Cost to Build a Custom Home in Seattle?
A custom home in the Seattle area runs about $400,000–$700,000+ all-in. Here’s what drives that number — and why the honest figure includes far more than framing.
Read the guideBuilding New vs. Buying a Home in Seattle: Which Makes Sense?
Build a custom home or buy existing? A clear-eyed comparison of cost, timeline, customization and value to help Seattle-area homeowners decide.
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Building on a Sloped or Difficult Lot in Seattle
Steep, wooded, or critical-area lots are common around Seattle — and they’re where budgets blow up without the right builder. Here’s what building on a difficult lot really takes.
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Can You Build a House and a DADU on One Lot?
Building a new home and a DADU at the same time can add income and value while saving on shared site work. Here’s how two homes on one lot works in Seattle.
Read the guideBuilding a Custom Home in Seattle: What to Expect
DIGS builds custom homes, not just ADUs. Here’s what to expect building a custom home in the Seattle area — cost, timeline, site work, and choosing the right builder.
Read the guideCost & Financing
11 guides
Selling a Home With an ADU: What Buyers, Appraisers and Lenders Look For
An ADU changes who buys your home and what the appraiser can count. The deciding factor is settled during construction, not at sale: whether the unit is permitted and documented.
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How to Compare ADU Bids Line by Line
The lowest bid is rarely the cheapest build. Here is how to compare scope rather than totals, and the three places a number gets quietly left out.
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Can You Airbnb an ADU in Seattle?
Seattle does allow it, but inside a two-unit cap, two licenses and a primary-residence test — and your CC&Rs or your insurer may say no even when the City says yes.
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Do You Need Special Insurance for an ADU?
The common surprise is the "other structures" limit on a standard homeowners policy — often a fraction of what a finished DADU would cost to rebuild. Here is what to check, and when.
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What Is the Cheapest Way to Build an ADU?
Some ADU savings are real and some just move the cost later. Which decisions genuinely lower the number, and the four things that cost far more to cheap out on.
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Can You Sell a DADU Separately in Washington?
Yes — but only one way, and it isn’t a lot split. Here is what RCW 36.70A.681 actually says, why a unit lot subdivision is closed to ADUs, and how a two-unit condominium works in Washington.
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Does Building an ADU Raise Your Property Taxes?
Adding a DADU adds assessed value, but state law offers a three-year exemption on the improvement — and it has to be claimed before the unit is finished. Here is how the numbers actually work.
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How Much Rent Can a Seattle ADU Earn?
A backyard ADU can pull real monthly rent in Seattle. What drives the number — size, location, finish — and how that income offsets the cost of building one.
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Renting Out Your ADU: A Seattle Homeowner’s Guide
A backyard ADU can turn unused land into monthly income. Here’s how renting one out works in Seattle — long-term vs. short-term, setting rent, and building to rent.
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Is an ADU a Good Investment?
Rental income, added home value, and a payback period measured in years — here’s how to think about the return on investment of building an ADU in the Seattle area.
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How to Finance an ADU in Seattle
You know what a DADU costs — here’s how people actually pay for one. A plain-English guide to home equity, HELOCs, cash-out refis, construction loans, and using future rent.
Read the guidePermitting & Process
22 guides
Getting Power to a DADU: Seattle City Light, Subpanels and Separate Meters
One of our clients spent months getting power to a finished DADU. The building was done; the connection was not. Here is how to make sure the electrical service is solved on paper before anyone pours a footing.
Read the guideWhat Happens If Something Goes Wrong After Your ADU Is Built?
Every building has a punch list. What separates builders is what happens after you hand them the keys back with a problem. Here is what to expect, what to put in the contract, and what Washington law says.
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What Happens at a Free ADU Consultation (and What to Have Ready)
The first conversation with an ADU builder decides whether the next six months are productive or a waste. Here is exactly what happens on ours, what to bring, and what to ask us.
Read the guideHow to Check Your Zoning Before an ADU: Seattle, King County and Snohomish County
Before anyone draws anything, five facts about your parcel decide what is possible. All five are public and free. Here is where to find each one and what to write down.
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Washington’s New Rural DADU Law (HB 1345): Building Outside the Urban Growth Area
For the first time, state law spells out how a county can allow a detached ADU on rural land. One unit per parcel, 1,296 sq ft, within 150 ft of the house, metered water and septic proof — and it is optional for each county.
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What Is an ADU Feasibility Study (and Why It Comes First)?
Every guide says “start with feasibility.” Here is what that study checks on your specific lot, what it hands back, what it cannot tell you, and why it is the cheapest step in the project.
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Should You Start an ADU Project in Winter?
The instinct is to wait for better weather. But permitting runs all winter, and it is the long pole — so the people who start in October are the ones digging in April.
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Can You Build an ADU on a Septic System?
On a septic lot the county health department decides this before the building department ever sees your plans. Here is the math a licensed designer runs, and what happens when the drainfield comes up short.
Read the guideDo You Need Fire Sprinklers in a Seattle DADU?
No code mandates sprinklers in a detached ADU. Access distance, fire flow and one unresolved water-service question are what actually decide whether you need them.
Read the guideCan an HOA Stop You From Building an ADU in Washington?
Your city can approve an ADU your HOA still forbids — they are separate systems, and a permit is not covenant permission. What Washington law actually changed, and what it did not.
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Seattle's Pre-Approved DADU Plans: Are They Worth It?
The City’s measured numbers: 61 days to permit a pre-approved DADU against roughly 160 for a conventional one. Here are the four eligibility gates, the real fee saving, and why a 2020 design may leave space on the table.
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Can a Tree Stop Your DADU? Seattle's Tree Protection Rules
A protected tree rarely stops a backyard cottage — it decides where it goes. Here are the tiers, the protection radius that comes out of your buildable area, and what the code gives back for keeping the tree.
Read the guideHow Big Can a DADU Be in Seattle?
The 1,000 sq ft cap is rarely what limits a backyard cottage. Setbacks, lot coverage and a single protected tree usually bind first — here is how the envelope actually gets decided.
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DADU Inspections: Every Inspection Your Build Goes Through
A permitted DADU is inspected at roughly a dozen checkpoints between the first shovel and the certificate of occupancy. Here is the sequence, what each inspector is looking for, and where builds actually stall.
Read the guideADU Rules Outside Seattle: Snohomish & King County
Almost every ADU guide online is written for Seattle city limits. If your lot is in Monroe, Bothell, Everett or unincorporated county, the rules that govern your build are different ones.
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ADU Utilities: Sewer, Water & Power Connections
A DADU is a full home, so it needs its own sewer, water and power. Here’s what ADU utility work involves — and why it’s one of the biggest cost variables on a build.
Read the guideADU Parking Rules in Seattle: What You Need to Know
Do you have to add parking for an ADU in Seattle? The rules loosened — here’s when off-street parking is required, when it isn’t, and what it means for your build.
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Do You Have to Live On-Site to Have an ADU in Washington?
The old rule said you had to live on-site to have an ADU. Washington rolled that back — here’s what the owner-occupancy change means, and why it makes renting far more practical.
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How Long Does It Take to Build a DADU in Seattle?
From first call to move-in, a DADU typically takes about 12–18 months. Here’s a realistic timeline — design, permitting, construction — and what changes it.
Read the guideCan I Build an ADU on My Lot?
Most Seattle single-family lots can fit a DADU — but it comes down to size, setbacks, coverage, trees and critical areas. Here’s how to tell if yours qualifies.
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Washington’s ADU Laws: What Changed and What It Means for You
Washington changed its ADU laws to tackle the housing shortage — more units per lot, no owner-occupancy requirement, reduced parking. Here’s the plain-English version for homeowners.
Read the guideDo You Need a Permit to Build a DADU in Seattle?
The permits you need to build a backyard DADU in Seattle, the zoning rules that decide whether you can build at all, and how long it really takes.
Read the guideReady to price your build?
Tell us about your lot and your goals. Eric follows up personally — the same person from the first call through final inspection. No pressure, no obligation.
- Owner-led — 37+ years, 100+ homes built
- Clear, line-item pricing · no hidden fees
- Serving Seattle, King & Snohomish County