Home addition cost by city
| City | Addition permits | Usual filed value | Middle half of firms' usual job | Usual days, issue to final | Reached final |
|---|---|---|---|---|---|
| Bellingham, WA | 131 | $66,413 | $48,212–$141,844 | 328 | 65.1% |
| Greensboro, NC | 393 | $66,975 | $44,000–$110,000 | 179 | 89.4% |
| Arlington, VA | 750 | $80,000 | $48,000–$232,500 | 235 | 88.5% |
| San Diego, CA | 671 | $85,351 | $61,775–$142,054 | 343 | 82.7% |
| Saint Paul, MN | 220 | $94,000 | $65,000–$150,000 | 429 | 54.0% |
| Naperville, IL | 299 | $94,500 | $72,500–$141,960 | 422 | 65.3% |
| Bend, OR | 181 | $97,000 | $100,000–$176,909 | 259 | 90.8% |
| Cincinnati, OH | 266 | $100,000 | $72,500–$229,000 | 443 | 56.0% |
| Minneapolis, MN | 404 | $100,000 | $120,000–$225,000 | 338 | 76.3% |
| Boulder, CO | 369 | $100,000 | $70,000–$313,436 | 415 | 78.0% |
| Honolulu, HI | 979 | $100,000 | $70,000–$175,000 | 567 | 59.3% |
| Columbus, OH | 329 | $113,269 | $75,154–$209,926 | 258 | 86.0% |
| Cary, NC | 303 | $125,000 | $59,100–$210,000 | 196 | 85.2% |
| San Francisco, CA | 674 | $230,000 | $207,800–$578,511 | 621 | 52.2% |
Each city's own page lists every firm with its usual addition: Columbus, Cary, Minneapolis, Arlington, San Diego, Greensboro, San Francisco, Boulder.
A few more cities file values but no complete timeline or firm band: Denver's usual addition was filed at $110,000, Cape Coral's at $125,000, Palo Alto's at $165,313 and unincorporated Marin County's at $250,000.
Read the range, not just the middle
The middle-half column takes every firm with three or more addition permits, finds each firm's usual job, and shows the band the middle 50% of firms sit in. It is wide everywhere. Arlington's runs from $48,000 to $232,500; Boulder's from $70,000 to $313,436. A firm at the bottom of the band mostly files small additions; one at the top mostly files large ones. Ask each builder what its last three addition permits were filed at, and whether they were the same kind of job as yours.
What moves an addition up the band is mostly written into the permit requirements. Arlington County lists what it needs before it will review an addition (Arlington County, read 21 October 2026):
| Arlington requires | When |
|---|---|
| Scaled plat with setbacks and easements | Every addition without a civil engineering plan |
| Stormwater (LDA) permit or civil engineering plan | Submitted with the building permit |
| Development plan | Land disturbance over 2,500 sq ft |
| Sealed structural calculations | Designs outside prescriptive code, or using shear walls |
| Mechanical plans | Any new HVAC system, or any addition over 500 sq ft |
| Asbestos inspection form | Any alteration or addition to an existing structure |
Most lines mean paying a designer, surveyor or engineer before a shovel moves. New windows, doors and circuits come with the job too; Bellevue, Washington requires plan review for "installing or moving an exterior door, skylight or window" (City of Bellevue, read 21 October 2026).
Why additions take most of a year
Additions are among the slowest permits we track. Greensboro (179 days) and Cary (196) close them in about six months; Minneapolis (338), Honolulu (567) and San Francisco (621) take from about eleven months to well over a year. The finished share shows the risk: only 54.0% of Saint Paul addition permits a year or more old reached a final, and 52.2% in San Francisco. An addition left without a final is unpermitted square footage at sale time. Put the final inspection in the contract as the last payment milestone.
Check an addition builder in five minutes
- Find your city's row and band above.
- On the Columbus addition compare page (or your city's), find the firm: additions permitted, finished share, licence status.
- Ask for two finished addition addresses and look up their final dates on the city's permit search.
- If you are also weighing a backyard unit, read ADU vs home addition before you sign.
See every Columbus addition builder by finished share →
What these numbers cannot tell you
The filed value is the builder's own estimate, and nobody audits it; finishes, appliances and trade work inside the addition may be on separate permits or left out of the figure. Cities do not record added square footage, so there is no per-square-foot figure here. Miami files additions together with remodels, so it is left out. Austin, Wilmington and Sugar Land record no values. Electrical, plumbing and HVAC permits on the same job are separate and not added in.
How we know this
Addition permits are those each city files under an addition work type over its three-year window ending September 2026 (a few cities end earlier; each city page names its window). The usual filed value is the median of permits that carry one; the middle-half range uses firms with three or more addition permits; "reached final" is the share of permits a year or more old that the city closed with a final; days is the median from issue to final. Permit requirements are quoted from the county and city pages under Sources, read 21 October 2026.
Numbers come from City of Columbus Building & Zoning Services permits on 1-, 2- and 3-family homes (the city's Accela permit layer); Town of Cary building permit applications (issued permits only); City of Minneapolis construction permits (CCS); Arlington County, VA building and trade permits; City of San Diego Development Services approvals; City of Greensboro building and trade permits; San Francisco DBI building permits on one- and two-family homes, with the contractor from the city's permit contacts file; City of Boulder construction permits, data through October 17, 2026. Nobody paid to be on this page and nobody can.
Questions
- How much does a home addition cost?
Going by permits, the usual addition was filed at $66,975 in Greensboro, $80,000 in Arlington, Virginia, $100,000 in Minneapolis, $113,269 in Columbus and $230,000 in San Francisco. That mixes small additions with large ones, so read your city's middle-half range too.
- How long does it take to build an addition?
From permit to final inspection, the usual addition took 179 days in Greensboro, 196 in Cary, 258 in Columbus, 338 in Minneapolis and 621 in San Francisco. Design and plan review come first and are not counted.
- Is an addition cheaper than an ADU?
In the permit record they overlap. An ADU adds a kitchen, a separate entrance and often its own utility connections; an addition extends the house you have. Our ADU vs addition guide puts both side by side for the cities that file both.
- How much does a room addition cost per square foot?
Cities do not record the added floor area on most addition permits, so we cannot divide value by size honestly. Ask each builder for the added square footage and the total price, and compare builders on the same basis; as a whole-job check, the usual addition was filed at $113,269 in Columbus and $100,000 in Minneapolis.
- What drives the cost of an addition up?
Going up instead of out, structural work on the existing house, and site work. Arlington County, Virginia requires sealed structural calculations for designs outside the prescriptive code, mechanical plans for any addition over 500 square feet, and a stormwater plan with the building permit.
Build your own list
Every firm with that kind of permit on record. Pick what you value. The list moves.
Related guides
- How much does it cost to hire a general contractor? Filed job values in 12 cities, and what the fee covers
- Design-build vs general contractor: one contract or two, and who may draw your plans
- Home remodel cost in 2026: what remodel permits were filed at in 18 cities
- Remodel vs rebuild: what remodel, demolition and new-home permits cost in 10 cities
For one city
- Residential permits — Arlington County, VA (accessed 2026-10-21)
- Work requiring permits — City of Bellevue, WA (accessed 2026-10-21)