What Size Barndominium Can You Build for Your Budget in Washington State?
The honest way to turn a budget into square feet is to take off everything that is not the house first, then divide what is left by a published cost per square foot. Most online answers skip the first step, which is why their numbers look generous. In Washington the first step is bigger than in many places: rural land near Puget Sound is expensive, a house needs proof of water before it gets a permit, a septic system comes with a permit from the local health jurisdiction, and when a contractor builds on your land, retail sales tax applies to the full contract price. This guide does the arithmetic in that order, using the Census Bureau's 2025 contract prices for the West, and then looks at small barndominiums, where Washington's energy code has a lower bar for homes under 1,500 square feet. The figures are other people's published data and simple arithmetic, not our pricing.
Figures below are industry data from cited third-party sources, not a quote from Washington Barndominium Builders. Every project is priced individually.
Bottom Line Up Front
- At the Census Bureau's 2025 West contract prices ($176.87 to $213.85 per square foot, land excluded), $200,000 builds roughly 935 to 1,130 finished square feet and $100,000 roughly 470 to 565 (arithmetic), and only after land, site work and sales tax are paid from somewhere else.
- A well, a septic system, a driveway and a power run cost about the same for a small house as for a large one, so on raw land they take a bigger share of a small budget.
- Washington's energy code asks for 5.0 additional efficiency credits for a dwelling under 1,500 conditioned square feet with less than 300 square feet of windows, against 8.0 for most homes, so keeping a small barndominium under that line lowers the bar.
Published cost figures
Third-party and government figures, each with its source. None of them is a quote, and none of them is ours.
| Measure | Range | Source |
|---|---|---|
| Contractor-built houses on the owner's land, West region, started in 2025: median to average contract price (land excluded) | $177–$214per sq ft | U.S. Census Bureau, Characteristics of New Housing 2025, Median and Average Contract Price per Square Foot of New Contractor-Built Single-Family Houses Started: West median $176.87, average $213.85 (read 27 Sep 2026) — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls |
| Construction cost alone, national builder survey, 2024 (no lot, overhead, marketing or profit) | $162per sq ft | NAHB, Cost of Constructing a Home 2024 (January 2025): average construction cost $428,215, about $162 per square foot; national averages only (read 27 Sep 2026) — https://www.nahb.org/-/media/NAHB/news-and-economics/docs/housing-economics-plus/special-studies/2025/special-study-cost-of-constructing-a-home-2024-january-2025.pdf |
Total cost by size
Rough totals at common sizes. These move with everything on this page, so treat them as a starting orientation, not an estimate for your project.
600 sq ft
$106,000–$128,000
Arithmetic, rounded to the nearest $1,000: 600 sq ft × the Census 2025 West contract price per sq ft ($176.87 median, $213.85 average); land, site work and sales tax excluded — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls
800 sq ft
$141,000–$171,000
Arithmetic, rounded to the nearest $1,000: 800 sq ft × the Census 2025 West contract price per sq ft ($176.87 median, $213.85 average); land, site work and sales tax excluded — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls
1,000 sq ft
$177,000–$214,000
Arithmetic, rounded to the nearest $1,000: 1,000 sq ft × the Census 2025 West contract price per sq ft ($176.87 median, $213.85 average); land, site work and sales tax excluded — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls
1,200 sq ft
$212,000–$257,000
Arithmetic, rounded to the nearest $1,000: 1,200 sq ft (a fully finished 30x40 footprint) × the Census 2025 West contract price per sq ft ($176.87 median, $213.85 average); land, site work and sales tax excluded — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls
1,500 sq ft
$265,000–$321,000
Arithmetic, rounded to the nearest $1,000: 1,500 sq ft × the Census 2025 West contract price per sq ft ($176.87 median, $213.85 average); land, site work and sales tax excluded — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls
2,000 sq ft
$354,000–$428,000
Arithmetic, rounded to the nearest $1,000: 2,000 sq ft × the Census 2025 West contract price per sq ft ($176.87 median, $213.85 average); land, site work and sales tax excluded — https://www.census.gov/construction/chars/xls/contractpricesqft_cust.xls
What actually moves the number
The land comes off the top
The Census contract prices exclude the land. If you do not already own the parcel, its price comes out of the budget first, and in Washington that can be most of it: the 2022 Census of Agriculture averages farmland with buildings at $38,716 an acre in King County and $4,951 in Spokane County.
Site work that does not shrink
The driveway, the building pad, the utility trenching, the well or water connection and the septic system cost about the same whether the house is 800 or 2,000 square feet. NAHB puts site work at 7.6% of construction cost on a typical lot; on raw rural land it is often a larger share of a small budget.
Sales tax on the contract
When a contractor builds on land you own, Washington retail sales tax is collected on the full contract price, at the state plus local rate for the location where the home is built; the Department of Revenue's Tax Rate Lookup Tool gives it for any address. Set it aside before dividing the budget by a cost per square foot.
The finish level
The Census figures are averages across every finish level. In NAHB's survey, interior finishes are 24.1% of construction cost, so the choice of cabinets, flooring and fixtures moves the square footage a budget buys more than the frame does.
Step 1: Take Land, Site Work and Tax Off the Top
Everything below the house has to be paid first. Budget it before you divide anything.
Land
If you still need the parcel, price it first. USDA's 2026 survey puts Washington pasture at $980 an acre and irrigated cropland at $10,000; the 2022 Census of Agriculture's county averages for farmland with buildings run from $929 an acre in Ferry County to $50,663 in Kitsap County. Building lots near the Puget Sound cities are priced by the lot, not the acre.
Water, septic, power and access
On raw land, get the water answer, a septic site evaluation, a power-line quote from the utility and a driveway price before you settle the house size. These are fixed costs of the parcel and they do not get smaller with a smaller house.
Permits and fees
Your city or county charges for the building permit and plan review, the local health jurisdiction for the septic permit, and a new exempt well in a Streamflow Restoration watershed carries the $500 fee set by RCW 90.94. NAHB's survey puts building permit fees alone at 1.8% of construction cost on a typical home.
Sales tax and a contingency
Washington retail sales tax applies to the full contract price when a contractor builds on your land. Keep a contingency on top for what the ground turns up; a budget that spends every dollar on square feet has nowhere to put a surprise.
How Big a Barndominium Can You Build for $100,000, $200,000 or More?
Divide what is left, not the whole budget, by a published cost per square foot. The ranges below use the Census Bureau's 2025 West contract prices: $176.87 per square foot at the median and $213.85 on average, land excluded.
$100,000
Roughly 470 to 565 finished square feet by the Census arithmetic. At this level most people are buying a shell kit to finish themselves over time, or a small cabin-sized plan with a well and septic they have already budgeted separately.
$200,000
Roughly 935 to 1,130 finished square feet by the Census arithmetic: a one- or two-bedroom home, or a larger shell with only part of it finished as living space.
$300,000
Roughly 1,400 to 1,700 finished square feet by the Census arithmetic, the range where a compact three-bedroom plan becomes possible. See the 3 bedroom barndominium plans.
$400,000 to $500,000
Roughly 1,870 to 2,260 finished square feet at $400,000 and 2,340 to 2,830 at $500,000 by the Census arithmetic. The median contractor-built house in the West in 2025 was 2,354 square feet, so this is where a typical family-size house sits.
Why the range is wide
The low end of each range uses the Census average, the high end the median. Your number moves with the finish level, the site and the local labor market, which is why a quote for your parcel replaces this arithmetic once you have one. The cost guide shows the other published benchmarks.
Small Barndominiums
There is no official definition of a small barndominium, or a mini barndominium. On this page it means roughly 600 to 1,500 finished square feet, often on one floor, sometimes with a shop bay or covered porch under the same roof.
What a small budget really buys
By the Census 2025 West arithmetic, 600 finished square feet comes to roughly $106,000 to $128,000, 800 to roughly $141,000 to $171,000 and 1,000 to roughly $177,000 to $214,000, before land and site work. The fixed costs of a rural parcel do not shrink with the house, so small plans make most sense where water, power and septic are already in place or cheap to add.
Stay under the energy code's small-home line
Washington's energy code treats a dwelling under 1,500 conditioned square feet with less than 300 square feet of windows and glazed doors as a small dwelling unit, which needs 5.0 additional efficiency credits instead of 8.0. Designing a small barndominium to stay under both limits is one of the few places where size changes the code's demands.
Kit homes, tiny homes and small barndominiums
Washington law defines a 'kit home' as 800 square feet or smaller and has directed the Building Code Council to write rules for that category by March 31, 2027, and the state's residential code includes the appendix for tiny houses. A small barndominium above those sizes is a house like any other, permitted under the full residential code. See barndominium kits.
Small plans to start from
The small barndominium plans and the 30x40 barndominium, a 1,200 square foot footprint, are the usual starting points. A custom plan can put the same area into a longer, narrower building if the lot or the view calls for it.
Stretch the Footprint with Unfinished Space
The cheapest square foot is the one you enclose but do not finish yet.
A shop bay under the same roof
A shop or garage bay needs no kitchen, bathrooms or interior finishes, so the building can be larger than the living area the budget allows. The living area is what the Census cost per square foot applies to.
Finish in stages
Some owners enclose a larger shell and finish part of it now and part later. Plan the plumbing and electrical routes for the whole building at the start, so the later phase does not mean opening finished walls.
Check the loan before you plan phases
Construction loans are written to finish a house, not a shell. Fannie Mae's single-closing construction-to-permanent rules cap the construction period at 12 months at a time and 18 in total, so a phase you plan to finish later may need your own money. See barndominium financing.
Reading this because you are weighing a build? The next step is a plan drawn for your program.
What's different in Washington State
The small-home line in the energy code
Washington's residential energy code requires additional efficiency credits on every new home: 5.0 for a small dwelling unit, meaning under 1,500 square feet of conditioned floor area with less than 300 square feet of windows and glazed doors; 8.0 for most homes; 9.0 above 5,000 square feet. A small barndominium designed to stay under both thresholds needs fewer options from the code's tables.
Water decides whether the budget works at all
A Washington building permit for a house needs evidence of an adequate water supply. On a lot with a water purveyor that is a letter; on rural land it is usually a well, and in the watersheds listed in the Streamflow Restoration Act a new home on a new exempt well pays a $500 fee and accepts a recorded withdrawal limit. Confirm the water answer before the parcel is bought.
Septic from the local health jurisdiction
Off the sewer, the septic permit comes from the county's local health jurisdiction after a soil and site evaluation, and the design reserves room for a replacement drainfield. The soil, not the size of the house, decides what kind of system you need, so a small house on poor soil can carry a large septic bill.
Washington's narrow 'kit home' category
Washington law now defines 'kit homes' as residential structures of prefabricated walls, floors and roofs assembled on site and 800 square feet or smaller, and has directed the State Building Code Council to write rules for them by March 31, 2027. Until then, and for any barndominium kit larger than that, the building is permitted like any other new house.
Pros and cons, honestly
Pros
- A small barndominium under 1,500 conditioned square feet with limited glazing needs fewer energy-code credits.
- A shop bay under the same roof adds usable space without the cost of finished living area.
- A clear-span shell can be enlarged inside later by finishing more of it.
- Smaller houses cost less to heat, cool and insure every year after the build.
Cons
- Wells, septic systems and driveways cost about the same for a small house as for a large one.
- Washington sales tax on the contract and rural land prices can take much of a small budget before building starts.
- Construction loans expect a finished house within a set period, which limits phased building.
- A very small home can be harder to appraise where there are few comparable sales.
How big a barndominium can I build for $200,000 in Washington State?
How big a barndominium can I build for $100,000?
How much does a small barndominium cost?
What is a mini barndominium?
Does Washington's energy code treat small homes differently?
Is a barndominium kit under 800 square feet a 'kit home' in Washington?
What size is the typical new house in the West?
Questions answered? Tell us what you want to build and we will put real numbers against it.
Sources
- U.S. Census Bureau — Median and Average Contract Price per Square Foot of New Contractor-Built Single-Family Houses Started (Characteristics of New Housing, 2025)
- U.S. Census Bureau — Median and Average Square Feet of Floor Area in New Single-Family Houses Completed (Characteristics of New Housing, 2025)
- NAHB — Cost of Constructing a Home 2024 (January 2025)
- USDA National Agricultural Statistics Service — Land Values 2026 Summary
- USDA National Agricultural Statistics Service — 2022 Census of Agriculture, Washington county data, Table 8
- WAC 51-11R-40620 — Washington State Energy Code, Residential: additional energy efficiency credits (R406.3)
- WAC 51-51-003 — Washington's adoption of the 2021 International Residential Code, including its appendices
- RCW 19.27.015 — State Building Code definitions, including 'kit homes'
- RCW 19.27.620 — rule making for kit homes
- RCW 19.27.097 — building permit applications: evidence of an adequate water supply
- RCW 90.94.030 — Streamflow Restoration: building permit fee and withdrawal limit
- WAC 246-272A-0200 — on-site sewage systems: permit from the local health officer
- Washington Department of Revenue — Construction industry guide: custom construction
- Washington Department of Revenue — Sales & use tax rates, including the Tax Rate Lookup Tool for any address
- Fannie Mae Selling Guide — B5-3.1-02, Conversion of Construction-to-Permanent Financing: Single-Closing Transactions
Keep reading
The pages that answer the next question this one raises.
How much does it cost to build a barndominium in Washington State?
The cost-per-square-foot benchmarks, county land values and Washington's own cost lines.
Read itBarndominium financing in Washington State
What a construction loan will and will not fund, including phased builds.
Read itSmall barndominium plans
Compact layouts to start from when the budget sets the size.
Read it30x40 barndominium
A 1,200 square foot footprint, a common size for a first barndominium.
Read itBarndominium kits
Shell kits for owners who plan to finish the inside over time.
Read itWant a real number instead of a range?
Start the survey and tell us about your land and what you want to build. Include the county and the parcel number if you have them, because in Washington the county zoning, the septic permit from the local health jurisdiction and the water answer change the budget more than the building does. The survey costs nothing.