How Much Does it Cost to Build an Addition?

Build an Addition Costs
Average reported costs
based on 2,632 cost profiles
Most homeowners
spent between
$21,674 - $62,925
Low cost
High cost

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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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