How Much Does it Cost to Build an Addition?

Build an Addition Costs
Average reported costs
based on 2,680 cost profiles
Most homeowners
spent between
$21,698 - $62,923
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Updated: August 22, 2015
The average national cost of adding a room or building an addition is $40,917, with most homeowners spending between $21,683 and $62,948. This data is based on actual project costs as reported by HomeAdvisor members.

Many homeowners eventually come to that daunting dilemma: whether to buy their dream house or transform their current home into that dream house. Once you make the commitment to add an addition, you've probably decided to go down the latter road. This decision might be something you've long considered, or it may have been thrust upon you by an expanding family. In either case, recognize that this will be a profound investment in time and money, but one that, if done properly, will enhance the value of your most important investment: your home.

Are Architects Needed for Additions?

It depends on the complexity of the addition. Are you adding a simple family room onto your home with one door into the rest of the house and one to the outside? A contractor should be able to handle it without the help of an architect. But if you're moving walls, redesigning the way one room flows into another adding a half loft and a spiral staircase or countless other complicated or intricate changes to your existing home, you may want to consider bringing an architect on board.
An architect will certainly add to your upfront costs on the project, but consider that a professional visual engineer can take your ideas and build them into something even more amazing. Also, by adding more clarity to your vision before construction starts, cost estimates will hit closer to the mark. When the project is done in partnership with an architect, you're also more likely to wind up with something that boosts your home values.

Will the Addition Add Value to Your Home?

Even if you have no plans to sell anytime soon, consider the resale value of your project. You might not always turn a profit on your home-expansion investment, but you should go into the job with realistic expectations about at least some kind of payback.
Because they're among the most expensive home projects, additions sometimes return less on your investment than remodels. But if you're significantly adding to the square footage of your home or adding important types of rooms, such as bedrooms and bathrooms, your investment may pay off considerably.

Size of the Addition

The size of your addition is the single largest factor in determining the cost of both labor and materials. The larger your addition, the more you will pay for wood, drywall, roofing, concrete, not to mention any interior touches you add in terms of wall, floor and window coverings. But don't let costs scare you into building a smaller addition than you really want or need. You can shave costs by using reclaimed or reused building materials, and the labor on a larger addition might not be significantly more than a smaller one. Talk over your options with your contractor to find ways to maximize size without blowing your budget.

Agree on Price and Payment Schedules at the Start

Get everything in writing. First, agree on a total amount.
It's reasonable for contractors to expect some money in advance, and then after specific milestones in the project. Be aware that shelling out too much money could put you at risk and giving too little could put your contractor at risk. It's a delicate dance, but one that should be precisely choreographed before anybody fires up the power tools.
Still, no matter how detailed your plan, remember that things happen. Find out about your contractor's change-order policy. Once you see your addition come to life, you may change your mind about the colors, fixtures, even the layout of the room. You may find that the contractor didn't understand your plan and made some decisions that didn't square with what you'd intended. Or the addition may run into problems neither of you could have foreseen. Each of these could have enormous effects on the cost of the project, and each can cause friction with your contractor. Minimize the conflicts by spelling out, as clearly as possible on the front end, how each of these contingencies would be handled.


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Mitch Wilson 16 days ago
Upstairs additions don't require a foundation or slab which reduces cost. Upstairs addiitons require more tear down, unless the house has a flat roof, which costs more. It really depends on how nice you make them...marble floors cost more than vinyl tile....but most places you can get additions done between 120-150 sq ft, custom houses 200-250 square foot. Be sure you balance what it costs to how much you can get out of it. Don't over build. Be careful not to pull down the value of a custom house by doing an addition that is lower quality than main house. Balance is the key.
Mitch Wilson 16 days ago
I just gave a homeowner an estimate for 21x33 family room addition plus a covered patio that will be 21x20. That's an additional 1100 square feet under the roof. My bid was $85k. It works out to $121 a square foot for the indoor living space and a free covered patio. Remodel is for Murfreesboro, TN.
hamid rezaei 7 months ago
Room addition cost about $210 per sq.foot and if there is a bathroom in addition you should add $5,000 in average and if there is a kitchen in addition you should add $10,000 in average to total price of $210 per sq.foot x sq. footage
joseph Hendri 5 months ago
thats fine my cost just off top of my head 80.000$ now i am not contractor just guess? give or take?
Richard Walworth 3 months ago
Just out of curiosity, what part of the country are you from? $210 seems high to me, but maybe not.
Brian D Kirkpatrick 4 days ago
Great information and very fast
linda haynes 14 days ago
Terry Ratliff 15 days ago
I just want a 16 x 22 family room addition to a mobile home. It will be added at the end to the house to follow the same roof line. Probably 2 large windows and a sliding glass door. Pergo flooring, cathedral ceiling, dry wall and paint. I'll take it from there
ALVIN JONES 3 months ago
looking to add second floor - how much should i budget for?
joseph Hendri 5 months ago
my neighbor just add this floor to his home? houses built 1923 so i have original molding floors i do not want the home to lose the integrity some modern but keep molding floors ect...
joseph Hendri 5 months ago
i was kind of expecting 80.00$ give or take? stairs thinking put spiral staircase in middle room? do not want large stepping to take up space? probably would use middle bedroom on second floor its small however back bedroom might work ?
joseph Hendri 5 months ago
have beautiful home big however we have very little closet space? the home i looked at before this home was smaller but the design was wonderful! they had 2 bedrooms on second floor? what made the house was third floor master bed and bath deck front and back of floor with large walk in closet? this house is about double the size! i would like to do the same only i want to have 2 bed bath decks with as much closet space i can get.
joseph Hendri 5 months ago
just bed bath closet x2decks as home is stone however second floor some siding some stucco? id prefer stucco? but i would like to see if contractor could build deck as he would build walls outside 3-4 foot higher as not to use trek board? more sturdy i like the look.
Ellen G Ericson 4 months ago
Looking to add a room where existing deck sits to be an extension of the house. Approx 15w x 13d. We want one exterior door, vaulted ceiling with 2 skylights. Windows flank centered door on side, Paladian-type window on rear peaked wall, one window on other side wall. Hardwood flooring. Does anyone have an estimate for what this type of project would run?