How much does it cost to build an ADU in Bellingham? The usual ADU job filed with Bellingham is $140,755, from 108 priced permits (October 2023 through September 2026); the middle half of firms file between $118,076 and $152,242. A filed value is what the contractor wrote on the permit, not a quote or the final bill.
The usual ADU job filed with Bellingham is $140,755, from 108 priced permits, October 2023 through September 2026. The middle half of firms usually file between $118,076 and $152,242. Half of jobs were filed for less, half for more. A filed value is what the contractor wrote on the permit, not a quote or the final bill. An ADU permit here usually takes 329 days from issue to final inspection. How long permits take →
Approximately, from each firm's own spread: every firm's range of filed values, weighted by its 108 priced permits across 70 firms, pooled into one. Half of Bellingham ADU permits were filed between $96,000 and $169,000.
| Percentile | Filed value | Reads as |
|---|---|---|
| 10th | $53,800 | 1 in 10 permits filed below |
| 25th | $96,000 | 1 in 4 filed below |
| 50th | $138,000 | the middle permit |
| 75th | $169,000 | 1 in 4 filed above |
| 90th | $335,000 | 1 in 10 filed above |
Firms split into thirds by the usual value of the homes they work on, with each third's usual filed value weighted by permits. Home values: Whatcom County Assessor appraised values.
| Firms working on | Usual home value | Usual filed value | Firms | Permits |
|---|---|---|---|---|
| Lower third | under $578,963 | $150,229 | 23 | 40 |
| Middle third | $578,963–$801,956 | $119,500 | 23 | 37 |
| Upper third | $803,612 and up | $127,758 | 24 | 32 |
Top 10 by permits in the last 12 months. Usual is each firm's middle filed value; middle half is the range its middle half of jobs were filed in; both are shown for firms with 5 or more priced permits. Busy is not the same as careful: pick what you value to build a list.
| Firm | Permits | Last 12 mo | Usual | Middle half | Finished |
|---|---|---|---|---|---|
| Myers General Inc | 4 | 4 | — | — | — |
| Bainbridge Construction LLC | 4 | 4 | — | — | — |
| Crim Brothers Construction LLC | 4 | 3 | — | — | — |
| Summit Construction Group Inc | 5 | 2 | $469,486 | $429,924–$484,366 | — |
| Champlain Custom Build LLC | 3 | 2 | — | — | — |
| True Bearing Built LLC | 3 | 2 | — | — | — |
| Z Construction Inc | 2 | 2 | — | — | — |
| Canyon Creek Building LLC | 2 | 2 | — | — | — |
| Blue Heron Woodworks | 6 | 1 | $74,832 | $55,856–$144,607 | 4 of 5 |
| Coffey Construction | 3 | 1 | — | — | — |
Line your quote up against the file. In Bellingham, 1 in 10 ADU filed values sit under $53,800, the middle half between $96,000 and $169,000, and 1 in 10 over $335,000.
Bellingham files the fewest ADU permits in May (33 against an average month of 100) and the most in March (174). If you can choose, ask for quotes in a quiet month. We have no prices by month, so this is about crews' schedules, not a discount. When each trade is busiest in Bellingham →
Source: City of Bellingham permits on single-family homes, duplexes and townhomes. The window is October 2023 through September 2026; a permit filed after that isn't here yet.
Usual is the middle permit: half were filed for less, half for more. Only permits with a filed value count; a value of $0 or none is left out.
The spread is approximate: we keep seven points of each firm's own range of filed values, not every permit, and pool them.
Nobody paid to be on this page and nobody can. How the records work in Bellingham →
ADU cost in other cities: Nashville Raleigh Denver San Diego Honolulu Palo Alto San Francisco Anaheim Marin County (unincorporated) Sacramento County (unincorporated)
Other job costs in Bellingham: New Home · Remodel & Repair · Fire Sprinkler · Addition