A stock-model ADU from My ADU runs about $190,000 to $275,000. A fully custom ADU generally lands between $250,000 and $350,000, sometimes more. That’s a wide spread, and the gap isn’t random — it comes down to your lot, your utilities, and how you finish the space. Here’s what actually moves the number, so you can see where your project is likely to land.
What that price actually covers
When you get a number from us, it isn’t just framing and drywall. It covers the design, the permitting, the site prep, the utility connections, and the build — all under one contract. That part matters, because the quotes that look cheapest are usually the ones leaving those pieces out.
A bare construction bid of “$180,000” can turn into a lot more once you add the architect, the permit fees, running water and power to the unit, and the landscaping to put your yard back together afterward. It’s one of the most common ways an ADU budget blows up: comparing an all-in price to a number that was never all-in. The honest figure is the total figure, and that’s the one we quote.
Stock model or custom: what you’re paying for
The biggest fork in the price is whether you build one of our stock models or design something custom.
Stock models are plans we’ve already drawn, permitted, and built. You get a proven layout, a shorter timeline, and a lower price — that $190,000 to $275,000 range. For a lot of families, especially anyone building for a parent who needs the space sooner rather than later, it’s the right call.
Custom is for when your lot or your family needs something the stock plans don’t cover: a specific footprint, accessibility features, a layout that works around a tricky slope. You’re paying for design time and flexibility, which is why custom starts around $250,000 and climbs from there. Neither one is better. It depends on your property and what you need the space to do. (Still deciding between an ADU and adding onto your house? We compared the two in ADU vs. Home Addition
What drives the price up
Three things move the number more than anything else.
Your site. A flat, open lot with room for equipment to get in is cheaper to build on than one with a steep grade, poor soil, or tight access. The ground itself sets your starting point.
How far your utilities have to run. Water, sewer, and power all have to reach the ADU. If those connections sit close, you save. If the unit goes at the back of a deep lot, the trenching and hookups add real cost.
Your finishes. The kitchen, the bathroom, the flooring, the fixtures — this is where two identical floor plans end up $40,000 apart. You control most of these choices, which means you have more say over the final number than you’d think.
Permit fees and system charges also differ between Vancouver, WA and Portland, OR, and even between jurisdictions within each. We price your specific city into the estimate rather than guessing at an average.
How to get a real number for your property
Ranges are good for planning. They aren’t an estimate. Two homes on the same street can come in thousands of dollars apart based on the three factors above.
Start with our ADU Investment Calculator for a rough sense of cost and the rental income an ADU could bring in. Then, when you want a real figure, we’ll walk your property, look at your lot and your utilities, and give you an honest, all-in number — not a teaser that grows later.
If you’re weighing that cost against years of assisted-living payments, or thinking about renting the unit out, the math often looks better than people expect. We laid out the income side in ADUs as Income Property.
Want a number for your own lot? Book a free consultation and we’ll give you a straight answer.
Last reviewed: September 2026.
By Luke Shaffer