How much does home addition cost in Marin County? The usual addition job filed with Marin County is $250,000, from 132 priced permits (October 2023 through September 2026). A filed value is what the contractor wrote on the permit, not a quote or the final bill.
The usual addition job filed with Marin County is $250,000, from 132 priced permits, October 2023 through September 2026. 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 701 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 132 priced permits across 119 firms, pooled into one. Half of Marin County (unincorporated) addition permits were filed between $97,200 and $498,000.
| Percentile | Filed value | Reads as |
|---|---|---|
| 10th | $25,600 | 1 in 10 permits filed below |
| 25th | $97,200 | 1 in 4 filed below |
| 50th | $251,000 | the middle permit |
| 75th | $498,000 | 1 in 4 filed above |
| 90th | $951,000 | 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: Marin County assessed land and improvement values from MarinMap parcels (Proposition 13 values, which usually sit well below market value). Under Proposition 13 a home bought decades ago can carry a value far below what it would sell for today, so treat the home-value matching and the price-versus-similar-jobs comparison as rough.
| Firms working on | Usual home value | Usual filed value | Firms | Permits |
|---|---|---|---|---|
| Lower third | under $1,622,005 | $150,000 | 39 | 44 |
| Middle third | $1,622,005–$2,686,390 | $230,000 | 39 | 40 |
| Upper third | $2,695,760 and up | $380,000 | 40 | 49 |
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 |
|---|---|---|---|---|
| G Family Construction Inc | 6 | 2 | $259,500 | $220,000–$371,000 |
| Rempe Steve General Contr | 3 | 2 | — | — |
| C L Construction | 1 | 1 | — | — |
| J G Construction | 1 | 1 | — | — |
| Artisan Timber Works LLC | 1 | 1 | — | — |
| Greenlief Energy | 1 | 1 | — | — |
| Buildrite Bay Area Inc | 1 | 1 | — | — |
| R De Leon Construction | 1 | 1 | — | — |
| Birdhouse Builders LLC | 1 | 1 | — | — |
| Symmetric Energy Inc | 1 | 1 | — | — |
Line your quote up against the file. In Marin County (unincorporated), 1 in 10 addition filed values sit under $25,600, the middle half between $97,200 and $498,000, and 1 in 10 over $951,000.
Marin County files the fewest addition permits in July (36 against an average month of 100) and the most in March (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 Marin County →
Source: Marin County Community Development Agency building permits on homes in unincorporated Marin (the County's open-data permit and inspection files). 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 Marin County (unincorporated) →
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
Other job costs in Marin County (unincorporated): Roofing · HVAC · Electrical · Solar & Battery · Kitchen, Bath & Remodel · Windows & Doors · Water Heater · Plumbing & Gas · Foundation & Retaining Wall · EV Charger · Siding & Stucco · Pool & Spa · Decks & Stairs · ADU