What’s the average cost to add a room?

You want to add a little more space to your house. But, you want to do it economically, without too many surprises. So, what’s the best way to figure out the average cost to add a room?

How big does the room need to be?

Maybe you are dreaming of a large sun lounge that spans the length of your house, but realize you could achieve your goals with one half its size? It’s a good first step to think through the room’s purpose and the size it needs to be to achieve it.

What is going in the room?

Depending on the purpose of the room, figure out what will be going into the room. If the room is a bathroom, it will have fixtures and sink, toilet, etc. If it is a den, it might have a closet, for example, or built in bookshelves. This will all be important detail when figuring out the cost. Other questions to consider are, what kind of finishes does it need? Does it need a tile floor, wood floor, carpeting or laminate?

How does the room connect into the house and the outside?

Does the room have doors to the outside? Windows? Is it connected to central A/C and heating? Does it have a separate energy system? What kind of foundation does it need? Thinking through the details of how it connects to the house and the outside will be necessary when figuring out costs.

Do you need to hire an architect?

If the project requires any sort of complexity, or, if you want to maintain continuity with your current design, it may be a good idea to hire an architect. An architect also communicates with the builder, makes sure that the room is being built to the correct specifications and manages construction and permitting issues. Learn why you might consider hiring an architect.

Are you legally allowed to build it?

You’ll want to figure out early on whether you are legally allowed to build what you have in mind. Also, what kind of permits do you need and what is the process with filings and approvals your area?

To find out whether you are legally allowed to build the room you desire, contact your town hall or department of buildings. Whether you can build the structure you want depends on local building rules. You’ll want to get a sense of what the process is up front so that you know how long the different approval steps may take.

If you plan to hire an architect, they will do this part for you.

Ask around for cost data, in order to find the average cost to add a room

Once you have all the details of the room you wish to build, a good idea of what’s going into it and whether you’ll hire an architect, it’s time to get cost data.

To do this, interview a number of builders. These can be casual conversations, as the costs you find may inform the scope of what you wish to build.

Just ask, for the room you are looking to build, what are some cost estimates? Try to find at least three builders to ask. This is the best way to figure out the average cost to add a room.

Because building costs change with the economic environment, it’s best to get recent estimates, so if you ask a friend who did a similar project, make sure that it was in the last year or so, and in the same region that you are in. Construction costs vary greatly depending on location.

Why you shouldn’t rely on “cost per square foot” estimates

Often I see in homeowner forums folks asking for the average cost to add a room, and people will quote a cost per square foot number. Such as, $200 per square foot. It might be tempting to take the square footage of your room and add a multiplier, but it’s really not a good way to get an accurate estimate.

The reason this is a bad idea is that there’s no real way to add it up on your own. Did you talk to an electrician or a plumber? All the different labor involved in your particular room make it unique, as well as finishes and components required.

It’s just not going to be a responsible estimate. And, most likely cost is the most important thing in determining if you want to go ahead and how. For most people, at least. If your room is 400 square feet and you estimate $200 per square foot and it ends up being $300 per square foot, well you’ve underestimated your budget by $40,000. That’s quite an overrun. You don’t want to make that mistake.

How to get estimates from builders

Get recommendations from friends, the local hardware store or just Google for builders in your area. Make sure that they have expertise in the type of project you are doing. I’d recommend talking to three different builders. Describe your project, with all of the pieces we’ve gone through above in this article. Get your estimates!

It’s free, and much more accurate that searching for data on price per square footage which probably won’t be relevant to your specific project anyway.

And, you’ll have a great baseline to decide if you want to move ahead with this project, scale down or scale up!