Solicit bids from 3-5 Seattle-DADU GCs

Where to find good GCs

You're looking for builders who've finished a DADU in Seattle in the last couple of years. There are three good places to look, roughly in order of usefulness:

1. Recent permit history. The SDCI Permit and Site History Research Tool lets you search by neighborhood. The contractor names that show up over and over on DADU permits are your local specialists. This is the single best list.
2. Your designer's short list. Your architect or designer has worked with several GCs on Seattle DADUs and knows who's good to work with. Ask. It'll be a short list, and it'll be biased toward GCs who collaborate well — which is what you want.
3. GCs who publish their work. Hammer & Hand, CAST, Microhouse, Ballard Backyard Cottages and a few others post detailed project diaries online. You can read how they think before you call them.

Aim for three to five bids. Three gives you a real comparison. Five gives you negotiating room. More than five and you're just creating work for yourself; fewer than three and you don't really know what the market is.

Send everyone the same package

This is the part that matters most: every GC has to be bidding the same thing. Otherwise you're not comparing prices — you're comparing different houses.

The "same thing" means:

• The same permit-ready plan set (same sheets, same revision, same date)
• The same allowance lines for finishes, fixtures, appliances, landscape — with the same dollar amounts called out
• The same exclusions stated up front (e.g., "no fencing," "no hot tub")

Here's a quick check: if GC A's bid has a "$15K landscape restoration allowance" and GC B's doesn't mention landscape at all, you're going to add $15K back to GC B's number when comparing. Spell out the allowance lines in your RFP and you save yourself that arithmetic.

Common allowance lines on a Seattle DADU:

• Site work and utility trenching
• Foundation (with a geotech-driven contingency if your soils call for it)
• Finishes — cabinets, flooring, fixtures, appliances
• Landscape restoration

Reading the bids when they come back

When three to five GCs price the same package, the bids will usually cluster within 10–15% of each other. That's a healthy spread.

If one bid comes in 25%+ below the rest, don't celebrate yet. In nearly every case, that gap is missing scope, not a more efficient builder — a foundation read that assumes simpler soils, a utility tie-in left out, an allowance line dropped. The fix is straightforward: walk the low bid line-by-line against the median, find the gaps, and add them back. If the bids match up after that, great — you may have found a better price. If the gaps were real scope, you've just saved yourself a stack of change orders.

What it actually costs in 2025–2026

The honest range right now is $400 – $700 per square foot, all-in. A typical 600–1,000 sq ft cottage lands at $400,000 – $650,000 turnkey.

You'll still see "$250K backyard home" headlines from around 2017 floating around. Don't budget against them — every recent retrospective puts the number well above that. Plan for the higher range and you won't be surprised.