Subtracting as You Add: The Costs of Building an Addition

Is your family outgrowing your space? Or is there a room you’ve dreamed of that’s not a part of your current floor plan? Whatever your reason, building an addition to your home can be a great way of making your livable space fit your lifestyle.

The big question—and we hear this one a lot—is, “How much will adding a room cost me?”

Good question, with a complicated answer. Building an addition, after all, is complicated; and without the right research and experience it’s hard to know what to expect—or how much you can afford.

For building a basic addition, we generally estimate between $250 and $325 per square foot. But before you start sketching blueprints, let’s dig a little deeper into what that price range entails.

First off, let me clarify that this estimate is based on a fairly simple project without excessive structural work or plumbing. But there are plenty of factors that can drive your cost up significantly. Before you start planning your addition, take the following points into consideration:

· Placement of the addition. Will you need to remove a significant portion of exterior wall? Or will removing a sliding glass door make the entrance to your addition less labor-intensive?

· Matching existing interiors. If you want your addition to blend in with your current flooring, for example, you’ll need to strip and refinish the old floor as you finish the new section for a seamless look. If this seems too intrusive into your current space, you might want to consider different flooring styles.

· Current utilities. There’s always a chance that your HVAC system or wiring won’t adequately cover your increased square footage. You may need to replace your HVAC unit, or upgrade your ductwork or electrical service. Depending on the specifics—size of your HVAC unit, required ductwork, etc.—this can bump your price up more than ten thousands dollars—without giving you an additional square foot of space. This can be an issue in older homes in particular, where these systems might be pushed to their limit as is.

· Matching exterior finishes. If your siding or brick has faded, it might not be possible to perfectly match your existing finish. Often brick that isn’t quite a match can be stained to more closely resemble older existing brick. If you’re looking to reduce expense, keep in mind that certain architecture styles might lend themselves to multiple types of exteriors. Find a builder who can think creatively about the look of your home.

· Complex roofing. Tying in your addition’s roofing can sometimes impact existing windows. They might need to be made smaller, be moved, or be removed altogether. This may not only impact the labor needed on the exterior of your home, but also the on the interior walls around those windows.

Keep in mind that there are other drivers of cost and some of them won’t reveal themselves until you’re fairly far along in the planning process. Consider also that the price range we listed above is for a basic single room (like a family room—nothing that requires plumbing). If you’re looking at higher end finishes or flooring, multiple stories, or substantial structural tie-ins, your cost will reflect these upgrades, potentially to the tune of $350 or more per square foot.

The best way to mitigate extra expense is to carefully plan how best to add extra livable space to your current floor plan within your budget. Talk to an expert and make sure they understand your needs and your price range. With some creative thinking and careful use of existing space and utilities, your new addition will add up to exactly what you want.