The national average cost of a room addition ranges from $10,000-$80,000. Your room addition project cost will depend on the number of square feet, material and construction costs, and repair work required on the existing structure to complete the add-on.
A room addition is a great option for homeowners who want a larger house, without buying a new home. Instead, the add-on expands the footprint of a home by building onto the existing floor plan or converting unused space. Adding a second story or converting a garage are two common examples.
Room additions also typically take less time, money, and work than a complete home remodel. Common add-ons include a home office, family room, expanded master bedroom suite, additional bathroom, walk-in closet, or guest room. Building an add-on not only boosts your home's resale value, it's also a smart move for growing families or those accommodating an aging relative.
If you're ready for more room in your house, this guide will help you estimate your bottom line on your new addition costs.
What's in this cost guide?
- What affects the cost of a room addition?
- Example room addition costs
- Tips for hiring a general contractor
The size of your addition, types of materials you use, prep work, and extra features (like built-in shelves) will all impact the total cost of your room addition. On top of labor and materials, you'll also need to pay for architectural plans and building permits.
Most contractors will estimate the total cost based on a price per square foot, which they calculate based on project scope, estimated labor costs, and materials. Here's a deeper dive into what affects the cost of a room addition.
The cost per square foot for new space can range from under $50 per square foot to $250 per square foot and higher. Most contractors offer an approximate price per square foot when bidding a house addition project. They base their estimate on:
- How large the project is
- What foundation work will need to take place (especially relevant for first floor home additions)
- What type of frame needs to be built
- Whether the project requires extensive plumbing and electrical wiring
- How complex the job is
The cost per square foot typically includes labor and material costs.
Labor costs can also be impacted by the cost of living in your area, since contractors also have to consider business overhead and other area costs. Room additions in expensive cities such as Manhattan or San Francisco cost more because of higher labor costs and costs of doing business than smaller areas or cities with a lower cost of living.
The materials used to build a home vary state by state. As an example, homes in Florida are often built from concrete block while homes in Georgia are built on a concrete foundation with wood framing. Because of these regional material differences, the cost for just for the frame, or shell, of a room addition can be $10–$20+ per square foot.
Material choices can also impact labor costs, since different materials require different types of skilled laborers. For example, stonework will require a mason and woodwork requires a carpenter.
Finishes are the final touches on your new living space. Finishes are the type of carpet or floor you have installed, the trim you choose, and the type of tiles you want—be it high-end marble or affordable ceramic. The more luxurious the finishes, the higher your home addition cost will be.
Some home additions require architectural drawings to properly equip contractors with building plans and to meet local building codes—and your vision. If you want a second or third story addition, an architect may be required.
Architects will either charge a percentage of the total construction costs for plans, a flat rate, or hourly rate. Average costs to hire an architect range between $875-$2,500, but can be higher depending on project scope.
Each home addition project is different. Everything from what general contractor you hire and how many windows you want, to the type of shingles you choose for your roofing can impact your addition cost. To help you better estimate and budget for this large home improvement project, here are some examples of construction costs of various different home addition projects:
200-square-foot room addition: $10,000
A Thumbtack pro based in Slidell, Louisiana charges an average of $50 per square foot for a standard room addition with contractor grade finishes. With the average room addition in Slidell, Louisiana being 10x19 that puts the total cost estimate at $9,500 before any additional finishes. Additional finishes can raise the cost another $8,000 - $15,000 or more.
The price per square foot includes the foundation, framing, drywall, interior and exterior paint, and standard flooring such as bedroom carpet. This also assumes that the homeowner provides any necessary fixtures for their new living space.
300-square-foot, upscale master bedroom expansion: $78,000
At $260 per square foot, this project by a Thumbtack pro based in San Jose, CA is a more expensive home add-on example. This was to build a master bedroom and bath expansion in Fremont, California.
The price per square foot included foundation work, framing, drywall, stucco, interior and exterior paint, and flooring. They also extended existing plumbing to the new bathroom. The project took approximately five weeks.
The customer paid an additional $5,000 for bathroom fixtures and flooring materials, bringing their complete costs to $83,000 to add a new bedroom with a spa-like master bath to their home.
300-square-foot luxury kitchen addition: $81,000
The same Thumbtack pro also completed a kitchen addition for a client at $270 per square foot. This project expanded the existing kitchen by 300 square feet. The price per square foot included foundation work, framing, drywall, exterior finish, interior and exterior paint, and extending the plumbing and electrical system. It also included the labor to install upgraded finishes, like high-end wood cabinets, white marble countertops, and top-tier appliances.
In addition to the $81,000 that the client paid the pro, they also paid for these additional finishes. For example, the material for the floors cost an additional $20,000 and their upgraded refrigerator was an additional $7,500. This brought the total costs up to $108,500.
The total project time was less than six weeks. One week was spent preparing for and pouring the foundation, one and a half weeks were spent framing, and two and a half weeks were spent finishing.
Unless you're acting as project manager, hire a general contractor who will oversee all parts of the project, making sure there is an electrician, a drywall contractor, a flooring professional, painters, and all other necessary specialists to complete your home addition. Whether you're adding on a family room or a garage, remodel costs aren't cheap. Make sure you spend right and find a qualified pro you trust.
It's also challenging to change contractors once you've signed a contract and paid a deposit, so doing your homework upfront pays off in the long run. Before you sign a contract you should:
- Verify your contractor's license. Most states require general contractors be licensed. As an example, the Washington State Department of Labor & Industries has an online license look up portal so you can verify your contractor and ensure they don't have any complaints lodged against them. For more information on smart hiring, check out our safety tips.
- Ask for references and read reviews. A great website and friendly face shouldn't be the sole reasons you hire a general contractor. Ask for references and read online reviews. Past experiences are important and can help you decide if this person or construction company are the right fit for you.
- Get clear on cash. After your free estimate, talk clearly about total project costs, what might cause the price to go up (unforeseen repairs, change orders mid-way through, etc.), and create a payment plan you both agree on. Never pay entirely upfront and be very wary of someone who asks for major money before completing work milestones.
- Sign a contract. Outline money, scope of work, timeline, and materials that will be used. The clearer the contract, the fewer problems down the line.
- Stay in the loop. Hire a general contractor who communicates with you frequently and makes sure you understand what is taking place throughout all stages of the home addition.
Whether you want to raise the roof of your house to transform your attic into a second-story living space, or expand the footprint of your cramped and cluttered kitchen, an experienced professional can help you build the home addition you've been daydreaming of. Find a general contractor in your zip code, as well as any other specialists you need, on Thumbtack.