Putting an addition on your house is expensive, but generally adds value when you get ready to sell it. Addition costs vary widely by region and by the size and type of an addition. It is cheaper to build up than to build out, so adding a room with a foundation is more costly than expanding an attic into a second story. Get specific estimates before you start a project.
Costs Vary Widely
Nationally, estimates of room addition costs vary from $80 to $250 a square foot. A simple room addition with a basic foundation and no plumbing generally costs at least $100 a square foot with typical internal finishing, no expansion of a heating/cooling unit, and minimal structural changes. The cost per square foot decreases as the size of the addition increases.
Basic Framing Expense
Framing an addition averages $6 to $8 a square foot nationally. That's the cost of building walls and adding or extending a roof with rafters or trusses. It does not include drywall, doors or windows, insulation, finishing trim or utilities. A 10-by-15-foot bedroom addition, for instance, might cost $900 to $1,200 just for framing.
Additions with Plumbing
An addition that includes a kitchen will require plumbing and boost costs. An addition with a kitchen can run $250 to $300 a square foot, not counting finishing details like appliances and countertops. An addition with a bathroom can cost $125 to $200 a square foot, again with a number of cost variables including type of flooring, shower and tub, plumbing appliances or custom lighting.
Have a Good Plan
Decide how much you can afford and adjust your addition to your budget, then get a good plan. Spending money up front on an architect to draw a detailed plan may save you some construction expense. Once you've decided on a size and type of addition, get estimates from at least three contractors, broken down by item (such as foundation, flooring, and drywall).
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