How much does it cost to add a second story?
$200 – $500 cost per square foot
$200,000 – $750,000+ cost to add a full second story
Cost to add a second story
The average cost to add a second story is $200 to $500 per square foot for materials and labor. A full second floor addition costs $200,000 to $750,000+, while a partial second story addition costs $100,000 to $250,000 on average. Adding a second story is a complex project requiring many different professionals.
|Project||Average total cost|
|Add a full second floor (1,000 SF)||$200,000 – $500,000|
|Add a full second floor (1,500 SF)||$300,000 – $750,000|
|Add a full second floor (2,000 SF)||$400,000 – $1,000,000|
|Partial second story addition (500 SF)||$100,000 – $250,000|
|Dormer addition||$19,600 – $54,900|
|Second story addition over garage||$60,000 – $200,000+|
Average cost to build a second story
The table below shows the average cost to build a 500-square-foot second story addition.
|National Average Cost||$175,000|
|Average Range||$100,000 to $250,000|
Second story addition cost calculator
The cost to add a second story depends on the square footage you're looking to add. Building a simple bonus room costs much less than doubling the home's square footage with a full second floor.
Full addition cost
A full second story addition costs $200,000 to $1,000,000+, depending on the square footage, features, and finishes. Adding a full second floor often requires major foundation and structural reinforcement to support the weight. Including a bathroom, kitchen, or laundry room increases the cost due to the added plumbing.
|Floor square feet||Average cost|
|1,000||$200,000 – $500,000|
|1,200||$240,000 – $600,000|
|1,500||$300,000 – $750,000|
|2,000||$400,000 – $1,000,000|
|2,500||$500,000 – $1,250,000|
Partial addition cost
A partial second story addition costs $60,000 to $250,000+, depending on the size and features. Partial additions involve removing part of the roof, adding a second floor to only part of the home, and re-roofing it. Partial additions often include a bedroom and bathroom to create a large primary suite.
|Square feet||Average total cost|
|300||$60,000 – $150,000|
|500||$100,000 – $250,000|
|700||$140,000 – $350,000|
The average cost to add a dormer is $19,600 to $54,900 and is worth considering if you only need a small amount of extra space. A dormer addition leaves the existing roofline, brings only a section of the roof out, and adds 25 to 250 square feet.
A bump-out or cantilever costs $10,000 to $30,000 on average. A bump-out expands a room by a small amount—sometimes just an extra 2 feet—and typically requires less structural work than other home additions.
Second story addition over garage cost
Building a second story addition over a garage costs $60,000 to $200,000+, depending on the features and finishes. Costs fall at the low end when adding a second-floor bonus room for extra office space or a play area and at the high end for a complete living space with a bathroom and kitchen.
Cost factors to add a second floor
Many factors affect the cost to add a second floor, including:
House age & type – Older homes may need additional reinforcements and repairs, or they may not be suitable at all to support a second story.
Remodel type – Adding a second floor with a bathroom, kitchen, or laundry room requires extending the plumbing lines, increasing the labor and material costs. The cost to add a bathroom alone is $18,000 to $47,000.
Custom vs. prefab – Modular additions cost less but offer fewer design options than a fully custom second-floor construction project.
Foundation – Many one-story homes do not have a strong enough foundation or footings for a second floor.
Structural support – Steel beam installation costs $100 to $400 per foot, including labor, materials, and the structural engineer's inspection. Your existing walls may need this added reinforcement to hold the weight of a second floor.
Extra outdoor features – Including a balcony or deck will increase the total project cost.
Relocation – A second floor addition requires contractors to partially or completely remove the roof. Don't forget to factor in the cost to rent a hotel or house during construction, as well as the cost to remove and store some or all the contents of the first floor.
Adding a second story is a complex project requiring a team of professionals. A general contractor charges $50 to $150 per hour or 10% to 20% of the total construction cost and typically hires and coordinates all the industry pros needed to complete the addition.
The table below shows the average hourly rates for the professionals you may need for your second-floor project.
|Professional||Average hourly rate|
|Planning & design|
|Soil technician cost||$40 – $110|
|Architect cost||$100 – $250|
|Structural engineer cost||$100 – $220|
|Interior designer cost||$50 – $200|
|Framing carpenter cost||$20 – $60|
|Electrician cost||$50 – $130|
|Plumber cost||$45 – $150|
|HVAC labor cost||$75 – $150|
A pre-construction geotechnical report costs $1,000 to $5,000 to confirm the land can handle the weight of a second story.
Structural engineering design plan fees range from $500 to $3,000+.
Blueprints cost $1,200 to $5,000 for a second story addition.
Construction permits cost $5 to $21 per $1,000 of the project cost or $0.16 to $0.74 per square foot to add a second story.
A second-floor addition requires the same interior structural components as any new build. The table below breaks down the typical interior costs:
|Framing cost||$11 – $30 per square foot|
|New electrical wiring cost||$4 – $9 per square foot|
|Insulation cost||$1 – $5 per square foot|
|Flooring installation cost||$6 – $10 per square foot|
|Interior painting cost||$1 – $3 per square foot|
|HVAC duct installation cost||$40 – $65 per linear foot|
|Window AC unit cost||$150 – $800 per unit*|
|Electrical outlet cost||$150 – $350 per outlet|
|Light fixture installation cost||$70 – $300 per fixture|
|New plumbing cost||$450 – $1,800 per fixture|
|Door installation cost||$155 – $688 per door|
In addition to the new second story construction, you'll need to make some first-floor modifications. At the very least, you need a staircase to access the new second floor. Some second story additions may include additional modifications, like replacing the windows to match the new story.
Building a staircase costs $1,000 to $5,000 for materials and labor.
Window replacement costs $450 to $1,500 per window installed.
Costs to complete the exterior construction for a second-floor addition include:
Is it cheaper to build up or build out?
Building up may be cheaper than building out if your home's existing foundation can already support a second floor. If your home needs structural reinforcement for the addition, building out may be more cost-effective. However, the lot size, soil type, and local laws may limit your options to one or the other.
|Project||Cost per square foot||Advantages||Disadvantages|
|Add 2nd story||$200 – $500||
|Home addition cost||$90 – $210||
|Attic conversion cost||$50 – $150||
Second story addition FAQs
Can I add a second story to my house?
You can possibly add a second story to your house. Your home's age, structure, and existing foundation, your property's soil makeup, and your area's building and zoning laws all impact whether adding a second story is possible or practical.
Contact a structural engineer or a contractor specializing in second-story additions to assess your home and determine your options.
How long does it take to build a second floor?
Building a second story takes 3 months to a year or more, depending on the size, features, and if the home needs structural reinforcement to hold the weight of the extra floor. Many other factors can also affect the timeline, including the permitting process, weather, material availability, and labor issues.
Is it worth adding a second story?
Whether it's worth adding a second story depends on the home and your specific circumstances. A second-floor addition is a huge project that takes months to complete and typically requires temporary relocation. You increase the home's square footage, but moving to a larger home instead may be more cost-effective.
Getting estimates from second floor addition contractors
Before hiring a home addition contractor for your second-story addition, be sure to:
Get 3 to 5 detailed second floor addition estimates to compare.
Hire a well-established company that is licensed, bonded, and insured.
Find a contractor or firm specializing in second floor additions.
Browse home addition contractor reviews on HomeGuide and Google.
Ask for local references and a portfolio of past similar projects.
Check local regulations, and your HOA if applicable, to confirm your addition complies with all building and zoning requirements.
Have a detailed contract and warranty in hand before the project starts.
Follow a payment plan instead of making a large payment upfront, and only make the final payment when the work is complete and has passed all necessary inspections.
Questions to ask
Building a second-story addition is a big undertaking with lots of moving parts. Asking the right questions can help ensure you hire the right contractor or design-build team for the job:
Are you licensed, bonded, and insured?
What experience do you have with second story additions?
What does the estimate include?
What additional costs could come up during the project?
Will my home's foundation need reinforcement?
Will you test the soil to confirm my land can handle the extra weight of a second floor?
How long will the project take?
Do I need to move out of the house during construction?
What permits do I need for this project, and do you handle the permitting process?