This page groups the guides by homeowner choice. It works whether one company handles the whole project or the owner hires several experts. Each guide shows what to check before spending more money.
Property screening: is there a credible project here?
Use the ADU site check before buying plans or asking for a firm price. It confirms the city or county and the buildings already on the lot. It also covers the possible footprint, trees, slopes, access and early utility routes.
The output should be a short written record of known facts, open questions and viable paths. It is not a universal score or a City determination.
New detached construction: what must the builder deliver?
The detached ADU guide treats a backyard cottage as a full building and site project. It covers early duties, the foundation, outside shell, systems and finishes. It also covers inspections and repairs to the yard.
Read it when comparing a custom DADU, an ADUniverse design, a local ready plan or a factory-built unit. The same construction costs remain even when the plans come from a different source.
Current-space conversion: what can really be retained?
The garage and basement conversion guide starts with an inspection, not promised savings. It checks the slab, frame, roof, moisture, ceiling height and openings. It also covers fire safety and utility routes.
The key choice is whether to convert, partly rebuild or choose another ADU type. Compare the finished home after all required work is counted.
Work connected to the house: how will the main home be affected?
Use the attached ADU guide for an internal suite or connected addition. It focuses on privacy, sound, independent entry, alterations to the occupied dwelling and choices about shared equipment.
The guide also explains why Washington projects should not borrow California’s different JADU terminology or rules.
Design path: should the project use a reviewed plan or original design?
The pre-approved versus custom guide compares four options. They are Seattle ADUniverse, another local ready-plan program, a factory-built unit and a custom design. The guide covers plan rights, allowed changes, the foundation and site documents.
The design and permits guide assigns the drawing, expert, filing and City-response duties. Read both guides before assuming “plans included” or “we handle permits” means a full service.
External work: where will power, water and waste travel?
The utilities and site-work guide covers work outside the unit. It includes power, water, side sewer, drainage and trenches. It also covers machine access, hauling and repairs.
Use it when the unit sits behind an occupied house or near mature trees. It also helps when the sewer route is unclear or machines must reach the backyard.
Financial planning: is the number complete enough to use?
The Seattle ADU cost guide is a budget tool, not a price list. It separates plans, fees, site work, structure, systems and indoor finishes. It also covers outside repairs, fixed prices, allowances and costs paid by the owner.
Use it to compare early options or to normalize detailed bids. A single price-per-square-foot figure cannot show which work has been left elsewhere.
Scheduling: what has to happen before what?
The timeline guide shows what must happen first. It covers owner choices, surveys, design, City review and utility work. It also separates builder time from delays caused by agencies, experts or the owner.
A schedule should show choice deadlines and prerequisites, not just a start month and a promised handover.
Company selection: are the offers genuinely comparable?
The builder comparison guide begins with Washington L&I identity and relevant project evidence. It then evaluates the planned team, document duty, exclusions, allowances, payment structure and change process.
It helps owners compare different business models. A state registration alone does not prove ADU skill.
Local permit office: which city guide belongs to the address?
Start with Seattle-area cities and counties when the permit office is unclear. There are hubs for King County and the Eastside. City guides cover Seattle, Bellevue, Kirkland, Redmond, Shoreline, Renton, Burien, Bothell and Mercer Island.
Those pages exist because their current sources, plan programs or property questions differ. They are not claims that one contractor has blanket coverage.
Prepare one handoff between stages
At the end of each stage, save the facts the next person needs. Include the permit office, plan date, open agency questions, utility assumptions, choices and budget. Rechecking the same facts wastes time and lets bids start from different points.
The project form can record the location, planned ADU, property facts and next goal for an early review.
Frequently asked questions
Must one company perform every stage?
No. Separate or integrated delivery can work. What matters is a written handoff and clear planning duties.
Which page should a new owner read first?
Begin with site check unless the site, city or county and planned route have already been documented.
Does publication of a city guide promise contractor availability?
No. Geographic capacity and project fit are checked separately for each inquiry.
Can I request bids before completing design?
You can request planning estimates. But label their assumptions. A reliable comparison requires bidders to price the same defined details.