Data through April 2026 · updated 20 Oct 2026
How much does home addition cost in Boulder County? The usual addition job filed with Boulder County is $60,000, from 177 priced permits (May 2023 through April 2026); the middle half of firms file between $50,511 and $194,952. A filed value is what the contractor wrote on the permit, not a quote or the final bill.
The usual addition job filed with Boulder County is $60,000, from 177 priced permits, May 2023 through April 2026. The middle half of firms usually file between $50,511 and $194,952. 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 addition permit here usually takes 279 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 177 priced permits across 119 firms, pooled into one. Half of Boulder County (unincorporated) addition permits were filed between $21,300 and $160,000.
| Percentile | Filed value | Reads as |
|---|---|---|
| 10th | $9,100 | 1 in 10 permits filed below |
| 25th | $21,300 | 1 in 4 filed below |
| 50th | $59,400 | the middle permit |
| 75th | $160,000 | 1 in 4 filed above |
| 90th | $366,000 | 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: Boulder County Assessor 2026 actual values.
| Firms working on | Usual home value | Usual filed value | Firms | Permits |
|---|---|---|---|---|
| Lower third | under $1,098,300 | $51,375 | 39 | 46 |
| Middle third | $1,098,300–$1,542,600 | $50,511 | 40 | 81 |
| Upper third | $1,551,100 and up | $73,500 | 40 | 53 |
Top 10 by permits in the last 12 months on file (May 2025–Apr 2026). 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 |
|---|---|---|---|---|---|
| Decks by Caio | 12 | 8 | $9,801 | $6,759–$14,729 | 76.1% |
| O'Keefe Built Inc | 10 | 4 | $50,511 | $32,288–$61,733 | — |
| Melton Design Build | 5 | 3 | $329,780 | $89,278–$400,000 | — |
| Ironwood Deck, LLC | 4 | 2 | — | — | — |
| Sobo Homes | 3 | 2 | — | — | — |
| Colorado Home Improvement | 2 | 2 | — | — | — |
| Sanders Construction | 2 | 2 | — | — | — |
| Outdoor Craftsmen | 4 | 1 | — | — | — |
| G Kenny Builders | 3 | 1 | — | — | — |
| Petra Custom Builders | 3 | 1 | — | — | — |
Line your quote up against the file. In Boulder County (unincorporated), 1 in 10 addition filed values sit under $9,100, the middle half between $21,300 and $160,000, and 1 in 10 over $366,000.
Boulder County files the fewest addition permits in February (58 against an average month of 100) and the most in April (143). 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 Boulder County →
Source: Boulder County Community Planning & Permitting building permits on homes in unincorporated Boulder County (the County's Accela permit layer, which stopped taking new applications on May 4, 2026, so the data ends with April 2026; the City of Boulder and the other cities issue their own permits), with issue dates and declared job values from the Boulder County Assessor's permit file. The window is May 2023 through April 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 Boulder County (unincorporated) → · Sources and definitions for every city →
Free to reuse with attribution (CC BY 4.0). Please credit Contractor Records and link to this page. Suggested citation:
Contractor Records, "Home Addition Cost in Boulder County (unincorporated), CO: what the permits say", https://contractorrecords.com/boulder-county/addition-cost, data through April 2026, from Boulder County building-permit records.Link to a table: The spread · By home value · Busiest firms.
Download the tables (CSV): Key figures · By home value.
From our cross-city data studies: the same measure, read the same way, for every city we cover.
Addition cost in other cities: Orlando Cincinnati Miami Minneapolis Denver San Diego Honolulu Albuquerque Boulder Greensboro Saint Paul Arlington, VA Scottsdale Somerville Cary Naperville Bellevue Cape Coral Bellingham Bend San Francisco Anaheim Columbus, OH Marin County (unincorporated) Little Rock, AR Bernalillo County (unincorporated)
Other job costs in Boulder County (unincorporated): Heating & Cooling · Roofing · Solar & Battery · Windows & Doors · Electrical · Plumbing & Water Heater · Remodel & Repair · Generator · Siding