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Adding a Home Office, Bedroom or Theater Room? How Much Does a Room Addition Cost?

At HomeLight, our vision is a world where every real estate transaction is simple, certain, and satisfying. Therefore, we promote strict editorial integrity in each of our posts.

You love your space, but honestly, you could use a little more space. If you add a home office, an ensuite, or just a few more feet to your kitchen, you could transform your house into a forever home. So around how much would a room addition cost? According to HomeAdvisor, homeowners spent on average $20,803 to $72,585 to add onto their homes. That’s a helpful start, but that’s a pretty big range.

To zero in on the most current average costs and how much of the cost you can hope to recoup when you sell, we spoke with several experts:

  • Allison Harris, a top real estate agent with Keller Williams in Savannah, Georgia, who has over 251 real estate transactions under her belt
  • Jerome Leyba, a top real estate agent for Keller Williams in Santa Fe, New Mexico, who specializes in new construction
  • Mark Poulton, a project manager at TraVek Inc. with 36 years of building an home remodeling experience
  • Jim Pitzen, a licensed architect and design consultant at the S.J. Janis Company

We break down room additions by the project to help you craft a custom estimate. Our comprehensive guide to room addition costs covers:

A notepad used to figure out the cost of a room addition.
Source: (Kelly Sikkema / Unsplash)

Room addition cost overview

Depending on the function of the room and the type of addition (ie, bathroom or home office, bump out or full addition), the size and cost of your addition will vary. Below is a list of the most common room additions and their costs. We’ll take a closer look at each project in the next section.

Home office: $18,000 – $35,000
Bump out: $1,700 – $18,900
Dormer: $43,801 – $75,563
Balcony: $600 – $2,400
Laundry room: $5,000 – $8,000
Mudroom: $10,000 – $14,000
Porch: $4,600 – $22,000
Sunroom: $10,000 – $80,000
Cantilever: $15,000 – $25,000
Garage: $22,000 – $43,000
Bathroom: $20,000 – $60,000
Kitchen: $13,300 – $37,500
Master suite: $25,000 – $100,000
In-law suite: $40,000 – $125,000
Theater: $70,000 – $90,000

Methodology

Angi analyzes homeowner surveys to determine average spending of completed home improvement projects.

HomeAdvisor gathers millions of real project costs from real homeowners in more than 10,000 U.S. cities and towns.

Fixr reviews cost information with experts in different fields of home improvement or design. They also check specialized publications, cost studies, and U.S. government reports.

Remodeling Calculator uses prices that are an aggregate of input from hundreds of pros across the U.S. as well as rigorous pricing research that is regularly updated.

In Santa Fe, it’s a huge bonus to homebuyers if the homeowner builds an additional bedroom or finishes out an unfinished space, adding heated square footage that can be used as an office space.
  • Jerome Leyba
    Jerome Leyba Real Estate Agent
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    Jerome Leyba
    Jerome Leyba Real Estate Agent at Keller Williams
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    Currently accepting new clients
    • Years of Experience 3
    • Transactions 125
    • Average Price Point $370k
    • Single Family Homes 106

Room addition cost by project

With the help of our experts, we determined the most asked-for room additions and calculated the costs and return on investment (ROI), when available. They include:

Home office

A home office is currently one the most commonly sought-after features of a home, according to Leyba. While there is increased demand for home offices, according to the Chicago Tribune, the added market value may not be what you’re expecting. However, a home office addition could be tax deductible if you’re self-employed.

If you must have the additional space, one of the best ways to save on the cost of a home office is to bump out a wall (see below for bump out costs). However, if you need to increase square footage with an entire room addition, you can increase the value of the addition if it can also serve as a bedroom — this means including a minimum of 70 square feet, a window, and closet in your home office.

Leyba explains, “In Santa Fe, it’s a huge bonus to homebuyers if the homeowner builds an additional bedroom or finishes out an unfinished space, adding heated square footage that can be used as an office space.”

  • Average ROI of home office: 53 – 75% if it qualifies as a bedroom
  • Average home office size: 50 – 150 square feet
  • Average home office cost: $100 – $200 per square foot

Bump out

Bumping out a wall is one of the most common ways to extend your living space. A bump out (also known as a micro addition) is also an economical way to increase living space without the need for additional supports or foundation. The cost to bump out a wall depends on the length and depth of the build. It’s difficult to determine the ROI of a bump out, however, there is added value in increasing the square footage of your home.

  • Average bump out size: 2 – 15 feet deep
  • Average bump out cost: $85 – $210 per square foot

Dormer

A dormer is a second story addition that is typically incorporated into an attic remodel. Built out from the slope of the roof, a dormer adds light, ventilation, space, and a fire escape to an attic or loft space. They also increase visual appeal and value of a home. A dormer will cost more per square foot if it’s a bathroom addition. While dormers have a low ROI, they have an added lifetime value of reducing electric bills.

  • Average ROI of dormer: 40%
  • Average dormer size: 240 square feet
  • Average dormer cost: $140 – 160 per square foot
  • Average dormer bathroom price: $160 – $170 per square foot

Balcony

Add value, appeal and outdoor living space to your home with a second story (or higher) balcony addition. The cost of a balcony addition depends on several factors, including: design, size, materials, type of balustrade or railing, and the contractor you hire.

  • Average balcony size: 40 square feet
  • Average balcony cost: $20 – $90 per square foot ($35 per square foot average cost)

Laundry room

If your laundry room is situated in a place that requires you to run up and down the stairs with a basket full of clothes, or if your washer and dryer are in a small closet off the kitchen or bathroom, you may be considering adding a laundry room to your home. Good thinking! A laundry room addition will add visual appeal and convenience and increase your home value.

Mudroom

A mudroom is an informal entrance/exit to your home, typically added to a side or rear entrance. A mudroom is used to receive muddy visitors, store coats, boots, and pet supplies. The cost to build a mudroom increases if the mudroom has a utility sink, washer and dryer, or if the space is heated.

  • Average mudroom size: 50 square feet
  • Average mudroom cost: $12,000
A deck that was added to a house.
Source: (S.J. Janis Company, Inc.)

Porch

With a typical ROI of 84%, a front porch addition is a great way to add outdoor living space, curb appeal, and value to your home. Some factors that will increase the cost of a porch addition include the addition of stairs and screens.

Sunroom

A sunroom is a great place to enjoy your morning coffee, nurture your plants, read a book, or kick back and relax. But the cost to add a sunroom to your home isn’t cheap. It’s the price of the windows that make a three-season sunroom costly. A four-season sunroom is even more costly, with the addition of insulation, heat and A/C, and sometimes plumbing.

Cantilever

Meant to add space to the home without encroaching on the yard space, a cantilever addition is a second story bump out that is supported by angled beams (cantilevers). Most cantilever additions can be constructed without major excavation for added cost savings. Cantilevers are typically meant to add space to an existing room, not to support an entire room, however sunrooms, laundry rooms, and balconies are common cantilever additions.

  • Average cantilever size: 2 – 15 feet deep
  • Average cantilever cost: $15,000 – $25,000

Garage

If your garage is too small or if your home was built without one, a garage addition may be just the answer. Some factors that increase the cost of a garage construction include the addition of heat, insulation, plumbing, storage, and finished walls. In the southwestern states, where carports are more common than garages, a homeowner can save on the cost of a garage addition by converting a carport, which already has a foundation and a roof.

Bathroom

A home with too few bathrooms can quickly become a battleground. When you add a bathroom, everyone in the home benefits from the added convenience and privacy. And as homeowners, you’ll benefit from the added value when you sell. But Poulton warns it’s common for bathroom additions to get expensive fast. “The bathroom is where homeowners tend to make the most changes mid-build, which increases the cost of labor, materials, and permitting.”

Kitchen

The cost of a kitchen addition or remodel depends on the design and the extent of the build – whether you’re starting from scratch or using the existing electricity and plumbing. The cost of tearing out a kitchen includes the cost for demolition and removal. You’ll also pay more for a custom kitchen. Keep in mind that when you remodel a kitchen, how much of the cost you’ll recoup when you sell depends on the price point and condition of your home.

  • Average ROI of kitchen remodel: 83%
  • Average kitchen size: 161 square feet
  • Kitchen cost: $75 – $250 per square foot (full remodel), $100 – $300 (new build) per square foot,  $125,000+ (custom build)
A bedroom that is a room addition.
Source: (S.J. Janis Company, Inc.)

Master suite

A master suite or ensuite adds significant space, functionality, comfort, and privacy to the home and may increase the value as well. Most master suites include a closet and a full bathroom. How much value an ensuite adds to a home depends on the size of the home and what’s typical of the market. If the addition is an over improvement, it would likely not add enough value to pay for the cost.

In-law suite

An in-law suite or accessory dwelling unit (ADU) typically features a bedroom, a bathroom, a kitchen, and a small sitting room. It is a small apartment, and may be attached or detached, usually with its own outside entrance. An ADU is a convenient space for homeowners to put up guests, adult children, or elderly parents.

Poulton estimates that the cost for an ensuite starts at $300 per square foot and goes up from there. “It’s the bathroom where things start to get expensive,” he says. “Anytime plumbing is involved costs go up, because the exact location of the existing plumbing in the wall isn’t always clear.”

And as Poulton explained above, bathrooms are where homeowners often make costly changes mid-build. According to Leyba, one floor plan that’s consistently used in Santa Fe’s new builds includes a casita (which is external and attached or detached) that is used as a mother-in-law suite or a home office. While the ROI of an ADU is entirely dependent on what’s typical of your local real estate market, it may be possible to recoup some of the construction cost by renting out the additional space while you are living in your home.

Theater room (media or game room)

A theater room is a great place to kick back and relax with family and friends. A home theater must be built correctly for the best acoustics, so you’ll pay extra for a designer and an architect. Our estimate below also factors in the cost of purchasing and installing the theater projector and sound system, which averages $17,500.

A sunroom that was added to a house.
Source: (S.J. Janis Company, Inc.)

Labor cost breakdown

The total cost for your project will depend on the size, location, complexity and quality of the addition as well as the typical cost for materials and labor in your area. Remember that your builder isn’t the only contractor involved in the project — you’ll also pay for subcontractors. For a more detailed picture, let’s dive into the average cost for labor:

Questions to ask contractor

When considering contractors for your project, you’ll get a better idea about the costs if you ask the following questions:

  • How do you calculate the cost of this project?
  • Is this a fixed-price contract with a detailed scope of work?
  • Will I pay more if the cost for materials goes up mid-build?
  • Do you pay the architect, subcontractors, and permitting?
  • What is the payment schedule?
  • How might I save costs in this build?
  • Do you have extra materials available for a discount?
  • What warranties or guarantees do you offer?
  • What might you run into that would increase the cost of the project?
  • What happens if I have changes after the build has begun?
  • How much value will this project add to my home?
A laptop and a phone used to ask questions to a contractor about room addition cost.
Source: (Anthony Choren / Unsplash)

Frequently asked questions about room addition costs

You have questions. Our experts have answers.

How can I save money on my home addition project?

There are ways to cut costs on your home addition, including:

  • Remodel an existing room
  • Convert an attic, basement, dining room, garage, carport, sunroom, porch, or patio into living space
  • Bump out an entry-level wall or adding depth to a second-story room with a cantilever or dormer
  • Utilize an existing door or window opening for the new doorway so structural changes don’t have to be made to external walls
  • Hire a design builder to manage all aspects of the project
  • Plan 90% of your budget toward the cost of labor and material – saving 10% of your budget for unexpected costs
  • Look into tax incentives and credits
  • Consider prefabricated options
  • Stick to the plan to avoid change order costs

Can I cut costs with a smaller addition?

Large home additions don’t always cost significantly more than smaller plans. Poulton elaborates.

“Homeowners are surprised to learn that they can’t save by building a smaller addition. While they’re using less in the way of materials, it’s still the same or similar amount of work for the builder. So, the cost per square foot goes down as the size goes up. Most homeowners opt for the larger addition at a lower price per square foot.”

Homeowners expend a large portion of their budget on the first stages of the build such as drawings, permits, wall removal, excavation, and foundation (if necessary). So doubling the size of your addition may only increase the overall price of the addition by a third.

Additionally, Pitzen points out that all professionals involved in the project will typically require a base payment for their services. For instance, an electrician may charge the same amount for wiring a 12 x 12 addition as they would a 15 x 15.

Is it cheaper to build up or build out?

It’s typically more cost-effective to build out rather than building up. When building up, your home structure must be reinforced to support the weight of the new addition and the roof must be replaced. If you’ve decided to build up, consider having the roof lifted to reduce the cost of building a new roof. Another way to save the cost of building up would be to convert an unfinished attic into living space, with a dormer or cantilever for additional space.

What does return on investment (ROI) mean?

Return on investment (ROI) is a tricky concept for homeowners. Simply put, ROI is the percentage of your cost you can hope to recoup at home sale. Very rarely will a homeowner recoup the entire cost of an addition or remodel. How much of the cost you’ll actually recoup depends on the amount you invest in the addition and what’s typical in your market when you sell. There are sometimes cases of extreme ROI exceptions. Leyba says he recently had a client who turned a $200K house into a $450K house by extending the garage and adding space to the back.

Estimate room addition costs and value in your market

Now that you have the average cost for your room addition, you can narrow in on a project estimate based on material and labor costs specific to your market. HomeAdvisor offers project cost calculators that factor in your location, addition size, and function (i.e. kitchen, bathroom, bedroom, etc.).

Leyba advises that when planning an addition to get the best ROI, a multipurpose room is typically going to add the most value, which means it must be heated, have a closet and an egress (window). In fact, not adding a closet or heating are two of the biggest mistakes a homeowner can make when adding on, which makes the addition a bonus room. Another mistake homeowners can make is not keeping the design and layout consistent with the rest of the home.

“If you’re using the cheapest materials you can find to cut costs and it doesn’t look like the rest of the home, you’re going to lose out on the value when you sell,” states Leyba.

If you’re looking for current, hyper-local intel into cost and value, it’s a good practice to meet with a top real estate agent experienced in additions and remodels in your area.

“What I specialize in is the impact of a renovation on the value of a home,” shares Harris, “I make spreadsheets and cost-benefit analysis to figure out exactly what kind of value you’re adding.”

A scale used to represent the cost of a room addition.
Source: (Fidel Fernando / Unsplash)

Weigh the cost of a room addition with the reward

Looking at the numbers, a room addition will set you back a pretty penny — so how can you decide if your efforts will be worth it?

“I think that anytime you do a major home improvement project, you have to look at it from two different lenses: the cost-benefit, meaning how much it’s going to cost and how much it’s going to increase the value of your home, but then also how much you’re gonna enjoy that space,” shares Harris.

For some objective expertise, reach out to a top real estate agent who can help you crunch your project’s return on investment. Equipped with a market-specific ROI estimate, you can determine whether it’s smarter to renovate or to sell and upgrade to a more spacious home.

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Header Image Source: (S.J. Janis Company, Inc.)