Room Addition Cost Factors
When budgeting for a room addition, there are many potential costs to consider, including expenses for architectural services, foundation materials, and flooring.
Architectural Services
If you want your addition to match the rest of your house, then you might need to hire a local architect, which typically costs $2,000 to $8,400.
Demolition and Site Prep
It usually costs around $1,300 to $5,100 to excavate, demolish, and prepare a construction site to build on.
Foundation Materials
Building a first-story addition requires laying a new foundation, which can cost you around $4,200 to $13,200.
Roofing
It usually costs around $80 to $100 per square foot to lay a new roof, so the bigger your addition, the higher your roofing costs.
Support Beams
Your walls need support beams to remain structurally sound, and these beams usually cost around $1,150 to $4,600 to install.
“Doorways from the existing house to the new space will need structural enhancement, as most external walls are load-bearing walls,” says Bob Tschudi, an Expert Review Board Member and general contractor. “As with any such change, it’s always good to consult with a structural engineer.”
Drywall
For walls to look like, well, walls, they need drywall, which costs around $1 to $3 per square foot.
Door and Window Installation
Doors typically cost around $1,000 to purchase and install, while windows range from $235 to $2,500, depending on the style and any customization.
Flooring
The cost of adding flooring to a room varies quite a bit by type and material, but it usually ranges from $1,500 to $4,500. Wood flooring typically costs the most, while vinyl and linoleum floors typically cost the least.
HVAC Installation
If you want to regulate the temperature of your addition, then you'll need to extend your existing HVAC system, which costs about $1,150, on average. “Your HVAC contractor can tell you if your existing HVAC system can condition the new space,” says Tschudi. “If not, you would need a larger HVAC unit or install a separate HVAC or a heating and cooling mini-split system in the new room.”
Electrical
Part of nearly any home addition cost is electrical installation. Expect to spend between $2 and $4 per square foot for wiring outlets and lighting. If reworking the home's existing electrical system, such as replacing an outdated service panel, is necessary to meet building code for the new room, expect an average additional cost of $1,150.
Plumbing
If your room addition also must include the cost to add a bathroom in the new space, expect plumbing installation prices to vary widely depending on the complexity of the addition and how it ties into the home's existing system. Plumbing costs will range from $1,000 to $10,000 to add a bathroom.
Painting
Your new home addition will likely require painting many or most surfaces, including walls, ceiling, and trim work. If that's the case with your addition, expect professional painting costs to range from $2 to $6 per square foot of finished space.
Framing
Even a small room addition will have a home renovation contract that includes the cost of framing the new space. Framing costs vary by project complexity and how the new structure will tie into the old one. Expect an average price of between $6 and $10 per square foot of the addition for framing.
Permits
Unless you're building your house addition yourself, your contractor will be responsible for obtaining and meeting the requirements for the permits necessary for your addition, and its cost will be part of your contract. The cost of building permits varies by location and project size and ranges between $150 to $2,000 in most situations.
How Much Does It Cost to Add on a Room by Size?
Your new room's size is one of the biggest factors that affect the overall cost. Basically, the bigger the room you want to add on, the more you can expect to pay for the project. Here's a breakdown of average prices by square foot.
| Room Size | Average Prices |
|---|---|
| 20’x20’ | $32,000 – $80,000 |
| 12’x12’ | $11,520 – $28,800 |
| 10’x12’ | $9,600 – $24,000 |
| 400 sq. ft. | $32,000 – $80,000 |
| 500 sq. ft. | $40,000 – $100,000 |
| 600 sq. ft. | $48,000 – $120,000 |
| 1,000 sq. ft. | $80,000 – $200,000 |
How Much Does It Cost to Add on a Room by Type?
Photo: Comstock / Stockbyte / Getty Images
Different rooms have different installation requirements, which can tack onto the cost of your addition. For example, if you're adding a primary suite with an attached bathroom, you'll need to pay extra for things like bathroom plumbing, which typically costs around $1,500 to $4,000.
Here's what you can expect to pay, depending on the type of room you want to add.
Cost to Add a Bedroom
Adding a bedroom to your home costs an average of $50,000, though it can vary greatly depending on whether you are repurposing a space or constructing a new room from scratch. Costs to build a new bedroom typically range from $30,000 to $100,000, but it can cost as high as $200,000 if for a large primary bedroom with special features like walk-in closets and a balcony.
Cost to Add a Bathroom
If you're looking to add a new bathroom, then you'll likely pay anywhere from $20,000 to $90,000, with the average cost of a 100-square-foot bathroom being about $75,000.
Even though bathroom additions cost more than some other types of rooms due to plumbing and fixture costs, they can also significantly increase the value of your home. In fact, depending on where you live, you can expect a 47% to 67% return on your bathroom addition investment.
Cost to Build a Primary Suite: Bedroom and Bathroom
Primary suites include a bedroom and a bathroom, so they're among the most expensive types of room additions. Costs for this project typically range from $30,000 to $100,000, but they can vary quite a bit depending on the details. For example, if you add a particularly large suite or high-end features, like custom cabinetry and marble countertops, the project can easily cost over $100,000.
Cost to Add a Kitchen
Like bathrooms, new kitchens require plumbing work, which adds costs. You'll also have to pay to install appliances, like your refrigerator and oven, unless you plan to take care of that yourself. Depending on your appliances, plumbing needs, kitchen size, and materials, the average cost of a 200-square-foot kitchen ranges from $48,000 to $95,000.
Cost to Add a Living Room or Dining Room
Because living room and dining room additions don't typically have plumbing or appliance needs, they tend to cost less to build than kitchens and bathrooms. The average cost of an 18’ x 12’ living or dining room ranges from $17,300 to $43,200. Adding elements like built-in furniture and high-end finishes will take you closer to the top of this range.
Cost to Add a Room Above the Garage
Adding a bonus room above the garage usually costs around $115 per square foot, with the average cost amounting to about $45,000. However, the cost of this particular project varies quite a bit based on factors like whether or not you need to build a staircase or change the structure of your existing garage. Significant structural changes can add $10,000 to $40,000 or more to the overall cost.
Cost to Add a Laundry Room
Because laundry rooms tend to be among the smallest rooms in the house, they're also some of the least expensive additions. Most people pay between $5,000 and $7,000 to add a laundry room to their home. However, if you decide to upgrade your appliances, replace or install a sink, or install more shelving, the cost can reach as high as $10,000 or more.
Cost to Add a Mudroom
Thanks to their typically small size and nonexistent plumbing requirements, mudrooms are usually the cheapest rooms to add on. A 36-square-foot mudroom addition typically costs around $3,600 to $7,200, depending on the type of flooring and storage you add.
Cost to Add a Sunroom
Sunrooms can be very basic, only designed for use during two or three seasons, or they can have extensive electrical, heating, and cooling needs. This wide variation means that the costs also vary considerably. Installing a basic, 200-square-foot three-season sunroom usually costs around $25,000, while a more extensive, all-season sunroom of the same size can cost $80,000 or more.
Cost to Add In-Law Suite
Adding an in-law room or rooms to your home can require numerous special considerations, including privacy and access concerns that could increase the project's cost. Expect a range of between $44,000 and $100,000, depending on the size and complexity of the in-law suite addition.
Cost to Add a Room to a House: DIY vs. Hiring a Pro
Typically, labor costs for a room addition amount to 30% to 50% of the project's overall cost. Hiring a contractor to add a room to your home typically costs between $50 and $100 per hour.
Pros of DIY Building a Room
The biggest perk of building a room yourself, without the help of a contractor, is cost savings. You can reduce or eliminate these costs by building part or all of the room yourself. For instance, if you decide to do the demolition yourself, you can potentially save $500 or more in labor charges.
Another significant benefit to doing the work yourself is that you can create the space exactly as you envision it—with all the personal touches and details.
Cons of DIY Building a Room
One con of doing this project yourself is that it is time- and work-intensive. Constructing a room also requires specific skills and tools, so you should weigh labor costs against just how much time you're willing to spend on the project and whether you have the ability to complete it to your standards. You're the one who'll be seeing it every day, after all.
Ways to Save Money on Room Addition Costs
Building a room addition, or hiring a home-addition contractor near you, can be a significant investment in both time and money. However, there are several ways to save cash on building your addition to help meet a project budget.
If possible, save up for the project to pay at least some of the costs without financing to avoid long-term interest charges.
Perform some of the demolition and finishing work yourself, such as painting and trim.
Stick to your pre-determined budget for fixtures and features.Obtain at least three price quotes from various contractors and avoid extremely low bids, as they're seldom as good of a deal as they appear.
Reuse items from your existing home if demolition is part of the plan, or get second-hand fixtures and features from re-use outlets at bargain prices.
If you're supplying some of the project's materials, shop around for sales and discounts at multiple retailers.
