Home addition cost in Janesville, WI
Local estimate from BLS wage data and BEA price levels. Reviewed Nov 4, 2026.
- Typical range (300 sq ft)
- $43,100 – $87,100
- Per sq ft
- $142 – $284
- before permit
- Versus US midpoint
- +13%
- US $57,500
- Rank of 300 metros
- #28
- 1 = most expensive
A home addition in Janesville, WI usually costs $43,100 to $87,100 for 300 sq ft. That works out to about $142 to $284 per sq ft before permits. Compared with the national midpoint that is $7,550 more. Carpenters earn a median of $36.24 an hour in the Janesville area, 24% above the US median of $29.12.
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Estimated cost for 300 sq ft in Janesville, WI, standard level
$56,300 to $73,900
About $185 to $241 per sq ft before permits. Labor is about 72% of the bill.
| Part | Low | High |
|---|---|---|
| Materials | $14,600 | $19,100 |
| Labor | $40,700 | $53,300 |
| Permits and fees | $890 | $1,450 |
| Total | $56,300 | $73,900 |
Cost breakdown for 300 sq ft in Janesville, WI
| Part of the job | Low | Midpoint | High | Share |
|---|---|---|---|---|
| Materials | $11,300 | $16,900 | $22,500 | 26% |
| Labor | $31,300 | $47,000 | $62,700 | 72% |
| Permits and fees | $470 | $1,150 | $1,850 | 2% |
| Total | $43,100 | $65,100 | $87,100 | 100% |
Where the Janesville price comes from
The wage side of the estimate leans on carpenters, who do 50% of the hours on a typical job. Their local median is $36.24 an hour. Add the other trades involved and the blended wage index for Janesville is 1.23 (US = 1.00), which puts labor at 72% of the total.
Materials are scaled with BEA's regional price parity for goods. Janesville is at 93.8 against 100 for the US, so a materials line of $18,000 nationally becomes $16,900 here (midpoint, 300 sq ft). Permits follow the all-items index of 93.7: $470 to $1,850.
Data note: 10% of the labor weighting for this project uses a statewide median because BLS has no published metro figure for that trade in Janesville. The wage table below marks each row.
What nearby projects cost in Janesville
Jobs that often go together with home addition are priced below at their usual sizes, using the same Janesville wage and price inputs. Compared with national midpoints, detached garage comes out highest (+9%) and kitchen remodel lowest (−1%); the gap comes from the trades each job uses.
| Project | Size | Range | vs. US |
|---|---|---|---|
| Kitchen remodel | 120 sq ft | $18,400 – $31,200 | −1% |
| Bathroom remodel | 45 sq ft | $5,000 – $24,800 | +6% |
| Detached garage | 576 sq ft | $31,600 – $63,400 | +9% |
| Roof replacement | 2,000 sq ft of roof | $6,650 – $13,200 | +7% |
What local crews earn in Janesville
The labor line is built from BLS wage data, one trade at a time. This job draws on 6 trades. We compare each trade's local median with the US median, weight the ratios by how much of the job each trade does, and apply the blend to the national labor cost. For Janesville the blend is 1.23.
Carpenters (47-2031), 50% of the weighting: a median of $36.24 an hour, 24% above the US median of $29.12. The middle half of them earn between $23.92 and $39.98 an hour. About 360 work in the metro. That is 51.5 per 10,000 jobs, compared with 43.1 nationally, which suggests plenty of local crews to bid.
Cement masons and concrete finishers (47-2051), 10% of the weighting: a median of $37.50 an hour, 37% above the US median of $27.41. The middle half of them earn between $29.43 and $39.04 an hour. About 100 work in the metro. That is 14.3 per 10,000 jobs, compared with 13.3 nationally, so the supply of crews looks typical.
For electricians (47-2111, weighted 10%) the local median is $39.51 an hour, which is 30% above the national $30.38. The middle half of them earn between $28.67 and $46.61 an hour. BLS counts 560 of them working in the area, 80.1 for every 10,000 jobs (US: 48.7), so the local bench is deeper than average.
Plumbers, pipefitters and steamfitters (47-2152), 10% of the weighting: a median of $38.01 an hour, 24% above the US median of $30.67. The middle half of them earn between $28.72 and $49.75 an hour. About 140 work in the metro. That is 20.0 per 10,000 jobs, compared with 30.0 nationally, so expect fewer local crews to bid.
Drywall and ceiling tile installers (47-2081) carry 10% of the labor weighting. BLS does not publish this trade for the Janesville metro, so we used the Wisconsin statewide median: $28.83 an hour against $28.33 for the US. The middle half of them earn between $23.05 and $33.42 an hour.
Roofers (47-2181), 10% of the weighting: a median of $30.44 an hour, 14% above the US median of $26.65. The middle half of them earn between $26.83 and $37.51 an hour. About 70 work in the metro. That is 10.0 per 10,000 jobs, compared with 8.7 nationally, so the supply of crews looks typical.
A quick sensitivity check: moving the lead trade (carpenters) from the median to the 75th percentile wage adds about $2,450 to the midpoint estimate; the 25th percentile takes off about $8,100. That is a swing of roughly 12.4% to 3.8% of the total, which is useful for judging whether a bid reflects wages or something else, such as scope or margin.
Janesville-Beloit has 69,870 jobs in total (BLS, May 2025), ranking 260th by size among the 300 metros on this site.
| Trade | Weight | 25th pct | Median | 75th pct | US median | Ratio | Level used |
|---|---|---|---|---|---|---|---|
| Carpenters (47-2031) | 50% | $23.92 | $36.24 | $39.98 | $29.12 | 1.24 | metro |
| Cement masons and concrete finishers (47-2051) | 10% | $29.43 | $37.50 | $39.04 | $27.41 | 1.37 | metro |
| Electricians (47-2111) | 10% | $28.67 | $39.51 | $46.61 | $30.38 | 1.30 | metro |
| Plumbers, pipefitters and steamfitters (47-2152) | 10% | $28.72 | $38.01 | $49.75 | $30.67 | 1.24 | metro |
| Drywall and ceiling tile installers (47-2081) | 10% | $23.05 | $28.83 | $33.42 | $28.33 | 1.02 | state |
| Roofers (47-2181) | 10% | $26.83 | $30.44 | $37.51 | $26.65 | 1.14 | metro |
| Blended | 100% | 1.23 | |||||
Janesville weather and the home addition calendar
Climate numbers on this page come from NOAA's 1991-2020 U.S. Climate Normals at the nearest suitable station, Afton - Janesville Wwtp (5 miles from the city center). They are 30-year averages, so any one year can run hotter, colder or wetter.
For digging, grading and setting material in the ground, the comfortable months in Janesville are April through October: 7 of 12. Outside them, January, February, March, November and December have an average overnight low at or below freezing (32°F).
In January, February, March, November and December the average low is at or below freezing, which means frozen ground and slower digging, compaction and sod or stone placement. NOAA counts about 148 days a year with a low at or below 32°F at this station.
Janesville gets about 37 inches of precipitation in a normal year, including roughly 37 inches of snow. The wettest months are June, July and August (5.0 inches in June). Inside the workable window, April and October are the driest, at 3.6 and 3.0 inches. The station averages about 13 days a year at 90°F or above.
We do not adjust the estimate by month, because we have no reliable published data on seasonal pricing. It is still worth asking contractors whether an off-peak start date changes their bid.
| Month | Avg high °F | Avg low °F | Precip (in) | For this job |
|---|---|---|---|---|
| Jan | 28 | 12 | 1.6 | Cold |
| Feb | 32 | 15 | 1.6 | Cold |
| Mar | 45 | 25 | 2.1 | Cold |
| Apr | 58 | 36 | 3.6 | Workable |
| May | 70 | 48 | 4.1 | Workable |
| Jun | 80 | 58 | 5.0 | Workable |
| Jul | 83 | 62 | 4.2 | Workable |
| Aug | 82 | 60 | 4.3 | Workable |
| Sep | 75 | 51 | 3.7 | Workable |
| Oct | 62 | 40 | 3.0 | Workable |
| Nov | 46 | 29 | 2.3 | Cold |
| Dec | 34 | 18 | 1.9 | Cold |
Cost by quality level and size in Janesville
The cited range is split into basic, standard and premium bands, then scaled to Janesville. Bands overlap, because plenty of standard jobs cost as much as a light premium one. Sizes run from bump-out (100 sq ft) to large suite (600 sq ft).
Basic
$43,100 to $60,700
Bump-out or simple room without plumbing
Standard
$56,300 to $73,900
Standard room addition with HVAC and electrical
Premium
$69,500 to $87,100
Large addition with bath or kitchen and a new foundation
| Size | Basic | Standard | Premium |
|---|---|---|---|
| bump-out (100 sq ft) | $14,700 – $20,900 | $19,300 – $25,600 | $24,000 – $30,300 |
| 20x20 room (400 sq ft) | $57,300 – $80,500 | $74,700 – $98,000 | $92,200 – $115,500 |
| large suite (600 sq ft) | $85,700 – $120,500 | $111,500 – $146,500 | $137,500 – $172,500 |
Home addition: what moves the price in Janesville
Plumbing and fixtures
Adding a bathroom or kitchen drives the price up the most.
Permits
Construction permits run $500-$2,000, or $5-$21 per $1,000 of project cost (HomeGuide).
Foundation
A foundation, framing, roofing and matching exterior finishes all have to be built before the interior work starts.
Is Janesville cheap or dear? The local comparison
Contractors rarely work more than an hour or two from home, so the neighboring metros set a rough ceiling and floor for your quotes. Midpoints for 300 sq ft range from $59,300 to $65,900 across Janesville and its five closest metros.
| Area | Range | Midpoint | vs. here |
|---|---|---|---|
| Janesville, WIthis page | $43,100 – $87,100 | $65,100 | |
| Rockford, IL25 miles | $43,600 – $88,200 | $65,900 | +1% |
| Madison, WI40 miles | $40,200 – $81,300 | $60,700 | −7% |
| Kenosha, WI60 miles | $40,100 – $81,100 | $60,600 | −7% |
| Milwaukee, WI65 miles | $40,500 – $81,900 | $61,200 | −6% |
| Racine, WI65 miles | $39,200 – $79,300 | $59,300 | −9% |
| Wisconsin (statewide) | $39,300 – $79,500 | $59,400 | −9% |
| United States | $38,000 – $77,000 | $57,500 | −12% |
Out of the 300 metros we cover, Janesville ranks #28 for the cost of this job (#1 is the most expensive). Statewide, Janesville is 9% above the Wisconsin figure.
Elsewhere in Wisconsin
| Metro | Size | Range | Midpoint | vs. here |
|---|---|---|---|---|
| Milwaukee, WI | 820,780 jobs | $40,500 – $81,900 | $61,200 | −6% |
| Madison, WI | 408,070 jobs | $40,200 – $81,300 | $60,700 | −7% |
| Green Bay, WI | 174,550 jobs | $39,400 – $79,600 | $59,500 | −9% |
| Appleton, WI | 124,230 jobs | $39,800 – $80,400 | $60,100 | −8% |
| Oshkosh, WI | 93,750 jobs | $44,700 – $90,300 | $67,500 | +4% |
| Eau Claire, WI | 86,060 jobs | $38,600 – $78,000 | $58,300 | −10% |
Metros of a similar size
Big cities and small ones price differently, so here is Janesville against the 4 metros with the closest total employment.
| Metro | Size | Range | Midpoint | vs. here |
|---|---|---|---|---|
| Lexington Park, MD | 70,650 jobs | $37,900 – $76,900 | $57,400 | −12% |
| Wausau, WI | 69,530 jobs | $37,000 – $74,900 | $55,900 | −14% |
| Bismarck, ND | 71,270 jobs | $35,600 – $72,100 | $53,800 | −17% |
| Yuma, AZ | 68,880 jobs | $33,500 – $68,000 | $50,800 | −22% |
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Home addition in Janesville: your questions
+How much does it cost to build a home addition in Janesville?
For 300 sq ft, expect $43,100 to $87,100 in the Janesville area. A standard-spec job lands at $56,300 to $73,900. Small jobs usually cost more per sq ft and large ones less.
+What is the price per sq ft for home addition in Janesville?
About $142 to $284 per sq ft for materials and labor, plus $470 to $1,850 for the permit if one is needed. The US range is $125 to $250.
+Is home addition cheaper in Janesville or Rockford?
Rockford is 25 miles away. The midpoint for 300 sq ft there is $65,900, which is 1% more than Janesville ($65,100). Wage and materials indexes both feed that gap.
+How much of the bill is labor in Janesville?
About 72% at the midpoint, or $47,000 out of $65,100. Materials are 26% and permits 2%. Nationally, labor is 67%.
+What would 20x20 room (400 sq ft) cost in Janesville?
$57,300 to $115,500. Pick a different size in the estimator above to get your own number.
+Does home addition need a permit in Janesville?
Often, but rules are set by your city or county building office, so call before you hire. Budget $470 to $1,850 for fees in the Janesville area (our national range of $500 to $2,000 scaled by the local price level).
+Is Janesville expensive for home addition compared with the rest of Wisconsin?
Janesville is 9% above the Wisconsin statewide estimate ($59,400 at the midpoint). We cover 12 metros in Wisconsin; see the state page to compare them.
+What do carpenters earn in Janesville?
The BLS median is $36.24 an hour in the Janesville area, compared with $29.12 nationally. The 25th to 75th percentile range is $23.92 to $39.98.
+What do basic and premium home addition work cost in Janesville?
For 300 sq ft, basic work runs $43,100 to $60,700 and premium work $69,500 to $87,100. Basic means: bump-out or simple room without plumbing. Premium means: large addition with bath or kitchen and a new foundation.
+When is the best time to build a home addition in Janesville?
Based on NOAA 1991-2020 normals, the comfortable months for this kind of work are April through October. April and October are typically the driest of those months. Local contractors' schedules matter as much as the weather, so book early for the busy months.
Home addition near Janesville
Where these numbers come from
Base prices are national ranges from the sources below. We scale labor by local BLS wages, materials by BEA goods prices and permits by the BEA all-items price level. Full method on the methodology page.
- HomeGuide: How Much Does a Home Addition Cost? (2026) (accessed November 4, 2026)
- Cost to Renovate: Renovation Labor Report 2026: Where the Money Goes (accessed November 4, 2026)
- HomeGuide: 2026 Building Permit Costs | Fees & Cost Calculator (accessed November 4, 2026)
- BLS Occupational Employment and Wage Statistics, May 2025
- BEA Regional Price Parities, 2024
- NOAA NCEI U.S. Climate Normals, 1991-2020
Note on derived figures: Materials = 32% of the installed price, from Cost to Renovate's mid-range 'Structural' category split (56% labor, 32% materials, 11% permits and design). It is a category average rather than an addition-specific figure.