How much to add extra room to house

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Adding a new room not only gives you and your family more space to live in, but it can also increase your home's value. However, room additions can get pretty pricey, so it's helpful to create a realistic budget before taking on this project. This guide outlines how much it costs to add a room to a house based on factors like where you live and what type and size of room you're building.

How Much Does It Cost to Add a Room to a House?

It typically costs between $20,900 and $72,600 to add on a room, but the cost can reach as high as $125,000 or go as low as $5,600, depending on things like materials, labor, and room type. The cost can also vary by location and whether or not you choose to do it yourself.

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. 

How Much Does It Cost to Add on a Room by Type?

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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 cost 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 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.

Room Addition Cost Breakdown

From installing plumbing and laying flooring to getting building permits, adding on a room requires many steps, and many of these components cost money. If you're curious about where you can save money through a DIY approach or you simply wonder where all of your money will go, here's a simple cost breakdown for an average-sized room.

• Bathroom plumbing installation: $1,500–$4,000

• Electrical: $320

• Wood flooring: $800–$1,000

• Carpet: $350

• Drywall: $400–$600

• Permitting: $400–$1,850

• Non-load-bearing wall demolition: $300–$1,000

• Load-bearing wall demolition: $1,200–$10,000

• Roof materials: $500–$5,000

• Roof framing: $700–$900

• Foundation installation: $4,000–$12,000

• Foundation materials: $400–$700

What Factors Influence the Cost of a Room Addition?

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.”

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. 

Frequently Asked Questions

Some people start the process before finding out if the addition is allowed by the municipality or other governing authority, such as a homeowners’ association. Tschudi advises that even if you have the land to extend your house, there can be restrictions, like easements, flood zones, HOA rules, historical preservation, and septic system tank sizes. Many homeowners start the planning process by having the property surveyed, which costs from $300 to $600.

The short answer is yes. Room additions almost always increase a home's value. But just how much they increase it varies by the materials you choose, the type of room you build, and other factors. For instance, adding a sunroom will yield you a 49% return on your investment, while adding a primary suite results in a 63% return on your investment.

First and foremost, you should consider whether you have the time and money to add a room to your home. Additions can be costly, especially if you hire a general contractor, so it helps to make a realistic budget.

If you decide to tackle the project yourself, just make sure you have the time and resources to finish it. Other factors for consideration include the type of room you want to add, how much that room will contribute to your home's resale value, and how much you're willing to spend on details like various finishes and materials.

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