AIM Builders / ADU construction / October 9, 2026
Planning an ADU on the Eastside
The questions to settle before calling an ADU builder: use, type, utilities, parking, permits and how the unit fits your lot.
Start with who the unit is for
Every ADU decision gets easier once you know who will live in it. A unit for aging parents has different priorities than a long-term rental or a space for an adult child saving for their own place. Accessibility, privacy, sound separation between the homes, even where the entrance faces: all of it follows from the answer to that first question. It also shapes decisions you cannot easily change later, like whether the unit shares laundry with the main house or has its own, and whether the kitchen is a full kitchen or a kitchenette. Write the answer down before you sketch anything. When the design questions start, and they will, the intended use is what settles them.
Detached, attached or a garage conversion
There are three basic forms, and they are different projects. A detached ADU is new construction in your yard: the most freedom in design, the most site work and the most separation from the main house. An attached ADU adds onto the home, sharing a wall and usually some systems, which can simplify utilities but complicates the structure. A garage conversion works with an existing shell, often the fastest path to a legal unit, but the space you get is the space the garage gives you, and the structure still has to meet current code for living space. Each form has real trade-offs in cost, timeline and permitting, and the right choice depends on your lot and your goal, not on a photo you saved.
Learn your lot's rules before drawing anything
ADU rules are local. Size limits, setbacks from property lines, height limits, parking requirements and owner-occupancy rules are set by each city, and across the Eastside and Puget Sound they are not the same. Redmond, Bellevue, Kirkland, Issaquah, Bothell and Seattle each publish their own standards, and some details vary lot by lot with zoning, critical areas or HOA covenants. Falling in love with a floor plan before knowing what your lot allows is the most common way homeowners waste design money. The research comes first: what can be built on your specific property, at what size, in what position. We review that with you as part of scoping an ADU construction project, before any design is finalized.
Utilities decide more than the floor plan
Sewer, water and power quietly shape every ADU budget. Where does your sewer line run, and can the new unit tie in without a long trench across the yard? Does your electrical panel have capacity for another dwelling, or does it need an upgrade? Is the water service sized for the additional demand? These questions have concrete answers, and they are cheaper to learn early than late. A unit sited close to existing connections usually costs less to serve than one at the back corner of the lot, which is one reason the walkthrough matters: the drawing board answers look different once you are standing in the yard.
Parking, access and life during the build
Cities may require off-street parking for an ADU, and even where they do not, your household will care where everyone parks once the unit is occupied. Construction access is its own question: materials and equipment need a path to the build site that does not destroy the landscaping or block your driveway for months. Think through how the two households will share the property afterward too: paths, fences, sight lines between windows, outdoor space that belongs to each home. The good news is that most ADU construction happens outside your house. You can live at home through nearly all of it, with interruptions limited to planned utility tie-ins.
Budget the whole project, not just the box
ADU budgets have three layers: the design and permitting work, the site and utility work, and the construction itself. Homeowners often price the third and forget the first two. Permit fees, connection charges, surveys and engineering are real line items, and site work like trenching, grading and foundations varies enormously from lot to lot. Because those variables are site-specific, we do not quote ADU numbers before seeing the property and researching its rules. A written, itemized estimate follows the site review, so the budget you plan around is built on your lot's actual conditions instead of an average from someone else's project.
What to bring to the first conversation
You do not need drawings to start. Bring your property address, a rough idea of where the unit could sit and what you know about your sewer, water and electrical service. If you have a site plan or survey from when you bought the home, that helps. So does honesty about the budget range you are working within and who the unit is for. From there the process is straightforward: we research what your lot allows, walk the property with you and put the scope, schedule and price in writing. If you are weighing an ADU, a free in-home consultation is the right first step.