How much does a second story addition cost?
A second story addition costs $200 to $500 per square foot on HomeGuide's figures and $100 to $300 on HomeAdvisor's.
Both are current, both are national, and they are not describing different jobs. HomeGuide publishes $200 to $500 or more per square foot and puts a full second floor at $200,000 to $750,000 or more. HomeAdvisor publishes $100 to $300 per square foot, says premium materials can push it to $500, and puts the whole job at $80,000 to $600,000 with a normal range of $100,000 to $250,000 and an average of $175,000. HomeGuide's own average for a 500-square-foot second storey is also $175,000, with a range of $100,000 to $250,000 — so the two agree almost exactly on the typical job and disagree on the rate. Where they disagree, this page prints both.
Sources: HomeGuide, HomeAdvisor
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.
Second story addition cost by size
| Project | Average total cost |
|---|---|
| Partial second story, 300 sq ft | $60,000 – $150,000 |
| Partial second story, 500 sq ft | $100,000 – $250,000 |
| Partial second story, 700 sq ft | $140,000 – $350,000 |
| Full second floor, 1,000 sq ft | $200,000 – $500,000 |
| Full second floor, 1,500 sq ft | $300,000 – $750,000 |
| Full second floor, 2,000 sq ft | $400,000 – $1,000,000 |
| Full second floor, 2,500 sq ft | $500,000 – $1,250,000 |
Source: HomeGuide
HomeAdvisor's own by-size rows read lower on the same footprints — $80,000 to $240,000 at 800 square feet and $100,000 to $300,000 at 1,000 — and it puts a full addition to a standard 1,500-square-foot home at $150,000 to $450,000 with a partial addition averaging $300,000. Two published tables, one job, and a gap wide enough that a homeowner should treat either as a starting point rather than a budget.
Source: HomeAdvisor
Why a second story is the most expensive addition there is
Because the house has to be made to carry it. HomeGuide's reason for placing this at the top of its addition table is the structural work: the builder modifies the foundation, the walls and the roof, and adding stairs can raise the architect or engineer fees. HomeAdvisor is blunter — it says most single-storey homes were not built to carry another floor, that reinforcing, repairing or replacing the foundation comes before framing starts, and that reinforcement and repair start at $5,000. HomeGuide prices the same work at $250 to $800 for minor foundation cracks, $2,000 to $20,000 for major issues, $20,000 to $100,000 to lift a house and replace the foundation, and $100 to $400 per foot for a steel beam with the structural engineer's inspection.
Sources: HomeGuide, HomeAdvisor
Both guides say the same thing about living arrangements: the roof comes off. HomeGuide says the family may have to leave the space for safety; HomeAdvisor says homeowners tend to arrange temporary housing for two to twelve months.
The cheaper shapes of the same idea
| Alternative | Average cost | What it is |
|---|---|---|
| Bump-out or cantilever | $10,000 – $30,000 | Extends a room outward, sometimes by two feet, with less structural work |
| Dormer addition | $19,600 – $54,900 | Brings out a section of the existing roof and adds 25 to 250 square feet |
| Second story over the garage | $60,000 – $200,000+ | A bonus room at the low end, a full living space with a bathroom and kitchen at the high end |
Source: HomeGuide
The professional fees are their own line and both guides publish them. HomeAdvisor says an architect charges 8% to 20% of the total project cost rather than an hourly rate, puts blueprints at $1,740 and a structural engineer at $550, and says a construction manager charges 10% to 20% to run the design, budgeting, permits and subcontractors. HomeAdvisor's permit figure is $1,200 to $2,000 and it adds $300 to $700 for post-construction cleaning. HomeGuide's addition guide puts building permits at $500 to $2,000 and house plans at $1,200 to $5,000.
Sources: HomeAdvisor, HomeGuide
To read both published second-storey bands against your own square footage: the home addition cost calculator.
On a job where two national guides differ by a factor of two, three local written quotes are the only figure that means anything. 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 it cost to add a second story to a 1,500 sq ft house?
- HomeGuide publishes $300,000 to $750,000 for a full 1,500-square-foot second floor at its $200 to $500 per square foot. HomeAdvisor puts a full addition to a standard 1,500-square-foot home at $150,000 to $450,000. Both are printed here because both are published.
- Is a dormer cheaper than a second story?
- Much cheaper on HomeGuide's figures: $19,600 to $54,900 for a dormer that adds 25 to 250 square feet without changing the existing roofline, against $100,000 to $250,000 for a partial second storey of 500 square feet.
- Do I have to move out during a second story addition?
- HomeGuide says a second-floor addition is more disruptive than other additions and may require the family to leave the space during construction for safety. HomeAdvisor says homeowners tend to arrange temporary housing, for two to twelve months depending on the project's complexity.
- Will my foundation hold a second story?
- HomeAdvisor says single-storey homes tend not to be built to carry another floor and that a contractor will likely need to reinforce, repair or replace the foundation before framing, starting at $5,000. HomeGuide prices minor crack repair at $250 to $800 and major foundation issues at $2,000 to $20,000. Only a structural engineer looking at your house can answer it.
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