How Much Does a Major Home Addition Cost?

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You bought your home because you fell in love with it. But families grow, desires change, and you might decide you want a little more space after some time. Maybe you’re thinking about selling and want to add some value to your house before putting it on the market.

You may have excellent reasons for wanting to make an addition to your home, but how practical is that idea? Unsurprisingly, it’s not cheap to make a major home addition. Every home addition varies by homeowner and home, but if you’re considering adding on to your house, you have to think about the costs and potential benefits.

Most of the time, adding a room or expanding a bathroom, kitchen, or living space is a good investment, but there’s a lot to consider before taking action. Here, we’ll help you understand what you’re getting into before you make an addition to your home and how to estimate if it really will add value to your home.

How much does a home addition cost?

HomeGuide estimates that the average room or house addition costs $86 to $208 per square foot. Most homeowners ultimately pay between $22,500 and $74,000 to add a room. HomeAdvisor estimates $80 to $300 per square foot and $21,075 to $69,887 for an addition. 

While those numbers are similar, there is a vast range depending on the type of project. Every home addition cost varies between homeowner and house and depends on a number of factors.

HomeAdvisor and HomeGuide break down the average costs like so:

Addition SizeHomeAdvisorHomeGuide
Average cost (all sizes)$21,075 – $69,887$22,500 – $74,000
Average cost per sq. ft.$80 – $300$86 – $208
12 x 12 (144 sq. ft. )$11,520 – $28,800$12,400 – $22,300
15 x 15 (225 sq. ft. )N/A$21,000 – $52,000
20 x 20 (400 sq. ft.)$32,000 – $80,000$34,400 – $83,200
600 sq. ft. $48,000 – $120,000$51,600 – $124,800
800 sq. ft. N/A$68,800 – $166,400
1,000 sq. ft. $80,000 – $200,000$86,000 – $208,000

Generally, more significant additions cost more since you’re adding more space and using more materials. That said, the final price tag depends on the type of space you’re building, the use of premium or more common materials, and where you want to add the addition, among other factors.

General costs for a home addition

Before we dig into specific types of home additions, there are some costs you can generally count on regardless of your exact project. According to HomeAdvisor, these are some of the basic expenses to budget for if you’re adding a room:

  • Design: An architect can help you design the addition to make sure it matches the existing home, meets local code, and looks great. An architect can cost anywhere from $2,000 to $10,000.
  • Permits: Many municipalities require permits for adding to your home. These can cost $400 to $2,000.
  • Excavation and site preparation: You will likely have to excavate and add a new foundation if you're expanding the first floor. Excavation could run anywhere from $1,500 to $5,000. Adding a new foundation costs $4 to $25 per square foot.
  • Roof: Unless your addition fills in an overhanging second floor, you’ll have to budget $75 to $600 per square foot for roofing.
  • Fixtures: Interior doors cost $250 to $1,150 each, windows are $250 to $1,000, drywall is $1 to $3 per square foot, insulation is $2 per square foot, siding and trim are $1 to $30 per square foot. Some additions may require extra budgeting for electrical work, plumbing, and purchasing and installing applications, too.
  • Flooring: Depending on the space, flooring could cost anywhere from $0.50 to $15 per square foot.

How much do different types of home additions cost?

Now that you have a general idea of what costs to consider in a home addition project, let’s look at some common types of additions and estimates from HomeAdvisor.

Again, project costs vary depending on placement, materials used, individual contractors, and more so remember you have some control over what you’ll pay for each.

Attic or basement

Converting an attic or basement into livable space can be a great move for your family. You might even be able to turn it into a rentable space to get some help with the mortgage. That said, it’s also one of the most expensive renovations you can do without physically adding space to your home. Converting an attic or basement into a livable space costs about $40,000 to $50,000, most often due to high costs to install insulation and ventilation.

Bathroom

Adding a bathroom is one of the best additions you can make in terms of ROI. (HomeAdvisor estimates a 53% ROI.) Bathrooms tend to be more expensive because of plumbing requirements and expensive fixtures like showers, sinks, and toilets. A 50 square foot bathroom will cost about $25,000 while a 100 square foot bathroom may range up to $75,000.

Bedroom

A bedroom addition costs around $50,000 and can range up to $100,000. However, HomeAdvisor estimates that a master bedroom and en suite bathroom addition carries a 63% ROI so it can be a smart investment.

Dining room

The standard dining room is 14” x 16” feet, ranging in cost from $20,000 to $45,000.

Kitchen

Kitchens are one of the most expensive additions since they require electrical work, plumbing, and appliances. For 200 square feet, expect to spend $50,000 to $100,000.

Living room

Adding a 12” x 18” living or family room costs about $20,000 to $45,000. Of course, the cost will go up as you add entertainment features and furniture to make it as comfortable and as fun an area as possible.

Mudrooms and sunrooms

For people who want to add storage space and organization, mudrooms and sunrooms offer great ROI at reasonable costs. They cost about $8,000 to $12,000 to add and carry a 49% ROI. As with any addition, the costs range just depending on how comfortable and climate-controlled you want each room and how fancy you’d like the fixtures.

Above the garage room addition

The space above a garage may seem like a wasted opportunity. Adding a guest room up there will cost about $115 per square foot, plus about $1,000 to add a staircase or pathway to connect the garage, upper room, and the rest of the house.

Garage

If you don’t have a garage in the first place, adding one to protect your car, give you additional storage, or have a workspace can be a great way to make your home feel a little more user-friendly. A garage addition typically costs $25,000 to $50,000 depending on HVAC and electricity desires.

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How to keep home addition costs in check

As is the case with anything in real estate, the more specific you can be about your wants and needs, the better you can plan your home addition budget. Before you begin any project, ask a few contractors to prepare bids for the project. Remember that the cheapest option isn’t necessarily the best. Contractors may try to save money by using lower-quality materials or underestimating the time it takes to do a particular task

Before hiring a contractor, go through the bid details with a fine-tooth comb and get all expectations in writing. If there are unexpected costs or an estimate is significantly lower than another contractor’s estimate, discuss the disparate numbers with each contractor. Eventually, you’ll have to trust your gut when choosing a contractor, but being thorough may help you suss out fishy contractors.

Additionally, these steps can help you save money throughout your addition:

  • Check with your homeowners insurer and state tax revenue office to see if your insurance or tax bill will rise as the square footage of the home increases. If you’re not sure how large an addition you want, these savings may help you decide.
  • Ask if a contractor has project management software. This type of software allows you to follow the project and budget. Transparency is key.
  • Explore companies like Renovation Angel which salvage appliances, cabinetry, countertops, and other pieces from luxury homes. You could get some luxury finishes and fixtures for a fraction of the original price.
  • Build a contingency budget in case things go wrong or you’d like to make changes. Setting aside 10% to 20% of the entire project cost estimate can help you avoid expensive, stressful headaches.

Keep in mind that, generally speaking, more significant additions carry a smaller price per square foot and may have a larger ROI than smaller projects. That doesn’t mean adding a comically large extra bedroom, but if you’re deciding between a 15” x 15” addition and a 20” x 20” addition, you may want to jump for the larger room if that makes sense for you.

Major home additions aren’t cheap. That said, some additions can add value to your home and most will add value to your life. After all, you wanted an addition to improve your home life in the first place. You can’t be guaranteed to recoup the full cost of any home addition project when you sell, but the enjoyment you’ll get from an improved home is priceless.

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