How much does a home addition cost?
A home addition costs $125 to $250 per square foot, or $50,000 to $100,000 for a 20x20 room addition, per HomeGuide.
That rate is for a new room built onto the house. HomeGuide's own table of addition types spans a much wider range than the headline suggests — $85 to $200 per square foot for a bump-out that pushes an existing room outward, $50 to $150 for an attic conversion, $50 to $100 for a basement conversion, $50 to $200 for a garage conversion, $100 to $300 for an ADU addition, $100 to $350 for a sunroom, and $200 to $500 or more for a second storey. The kind of addition decides the number more than the square footage does.
Source: HomeGuide
This page is general information, not professional advice. Remodeling prices move with your local labor market, the condition of what is already there, the finishes you pick and what your building department requires, and the only number that counts is a written quote from a contractor who has walked the job.
Home addition cost by footprint
| Footprint | Square feet | Average cost |
|---|---|---|
| 10 x 10 ft | 100 | $12,500 – $25,000 |
| 12 x 12 ft | 144 | $18,000 – $36,000 |
| 10 x 20 ft | 200 | $25,000 – $50,000 |
| 20 x 20 ft | 400 | $50,000 – $100,000 |
| 20 x 30 or 15 x 40 ft | 600 | $75,000 – $150,000 |
| 20 x 40 ft | 800 | $100,000 – $200,000 |
| 25 x 40 ft | 1,000 | $125,000 – $250,000 |
Source: HomeGuide
So a 20x20 home addition costs $50,000 to $100,000 on HomeGuide's table and a 10x10 costs $12,500 to $25,000. Every row on that table is its $125 to $250 rate carried across the row's own area, which is worth knowing for two reasons: a footprint between the rows can be read off the same rate, and the price does not fall as the addition gets bigger. HomeGuide's own descriptions place a 10x10 as adequate for a child's bedroom, a home office or a craft room, a 12x12 as a roomier guest bedroom, and a 20x20 as a family, living or dining room.
Source: HomeGuide
To price your own footprint and addition type against those published tables: the home addition cost calculator.
Cost to add a room to a house, by room
| Room | Typical size | Per square foot | Average total |
|---|---|---|---|
| Bathroom | 40 – 50 sq ft | $175 – $225 | $7,000 – $11,000 |
| Bedroom | 120 – 140 sq ft | $125 – $175 | $15,000 – $25,000 |
| Family or flex room | 200 – 225 sq ft | $125 – $175 | $25,000 – $40,000 |
| Kitchen | 100 – 200 sq ft | $200 – $250 | $20,000 – $50,000 |
| Primary suite | 300 – 600 sq ft | $150 – $225 | $45,000 – $135,000 |
| Sunroom | 150 – 300 sq ft | $100 – $350 | $15,000 – $105,000 |
Source: HomeGuide
Plumbing is the line that separates the cheap rooms from the expensive ones. HomeGuide's bedroom and family-room bands sit at $125 to $175 per square foot; its bathroom band is $175 to $225 and its kitchen band $200 to $250, on rooms a fraction of the size. A primary suite at $45,000 to $135,000 is expensive because it is two rooms, one of which is a bathroom.
Source: HomeGuide
The cheapest square footage you can add is the square footage already under your roof. An attic or basement conversion runs a third of what a new room does on the same published table.
What you spend before the build starts
| Line | Average cost |
|---|---|
| House plans | $1,200 – $5,000 |
| Land survey | $400 – $1,800 |
| Site excavation | $1,500 – $5,000 |
| Grading and levelling | $1,000 – $5,000 |
| Foundation | $2,400 – $10,500 |
| Building permits | $500 – $2,000 |
Source: HomeGuide
HomeGuide names what moves a quote off its table and prices none of it as a multiplier: the size, the complexity of the design, local zoning and impact fees, whether the addition needs plumbing on top of electricity and heating, the finishes, and delays from permitting, weather or material shortages. Its guidance on value is that any addition which increases the home's square footage should increase its value, and that a homeowner can expect to recoup about 60% to 80% of the cost at sale depending on the type.
Source: HomeGuide
Compare several estimates on the same size, the same materials and the same features — HomeGuide's own advice, and the only way the spread above becomes readable. These are the general contractors AI assistants actually name when homeowners ask. Nobody can pay to be on these lists.
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Questions people ask next
- How much does a 20x20 home addition cost?
- HomeGuide publishes $50,000 to $100,000 for a 20x20 room addition — 400 square feet at its $125 to $250 per square foot — and describes that footprint as more than adequate for a family room, living room or dining area.
- Is a bump-out cheaper than an addition?
- On HomeGuide's table, yes: $85 to $200 per square foot for a bump-out against $125 to $250 for a room addition. HomeGuide's explanation is that cantilevering a small bump-out off the existing foundation, with no footings or foundation walls, is what saves the money.
- Does a home addition increase property value?
- HomeGuide says yes, that any addition increasing the home's square footage should increase the property value, and that a homeowner can expect to recoup about 60% to 80% of the cost of the addition when the home sells, depending on the type.
- How much does it cost to add a bedroom to a house?
- HomeGuide publishes $15,000 to $25,000 to add a bedroom of 120 to 140 square feet, at $125 to $175 per square foot. Adding a primary suite instead runs $45,000 to $135,000 on HomeGuide's table, because the suite includes a bathroom.
Written for homeowners by Most Recommended Contractors, which measures which general contractors AI assistants actually recommend in 26 U.S. metros. Nobody can pay to be on those lists. How we measure.