Home Addition Cost Breakdown

Home Addition Cost Estimates

The average cost for a home addition ranges from $20,807 and $72,535. The type of home you’re adding onto can vastly impact your final cost.

Cost to Add on to a Ranch House

Expect to pay from $80 to $200 per square foot to add a room to your ranch house. You typically have two options for this project: build out or build up.

Build out

• More expensive.
• Involves adding a room at ground level and extending the home’s perimeter outward.
• You’ll need to pour a new foundation.
• You will lose yard and property space
• You may have to get a zoning variance to complete the project.

Build up

• Less expensive.
• Includes adding a room to the second story – or adding an entire second story to a one-story home.
• You’ll need to pay to add a staircase to your home
• Your contractor may need to strengthen the existing foundation to support the extra weight.
• Always check to see if your town has rules regarding the height of your home.

Cost to Build a Second-Story Addition

Building a second-story addition usually runs between $100 and $300 per square foot. It can cost as much as $500 per square foot depending on the quality of materials and complexity of the project. A second-story addition often involves adding an entire level to your home, rather than just an extra room.

Prefab or Modular Addition Cost Per Square Foot

Adding a deck to a modular home costs around $25 per square foot. Doing this project yourself will help save on labor costs. But adding on to a prefab home can be tricky, so hiring a contractor is usually the best way to go.

Adding a whole room to a modular home is usually not recommended, as the prefab home may not be able to support it. Consult a pro to see if a room addition is an option for your space.

Cost to Add a Room to a House

Adding an average-sized, 20 foot by 20 foot room to your home costs between $32,000 and $80,000. That price increases if you choose to include any high-end fixtures or appliances. 

Cost to Add a Bedroom to a House

It costs between $80 and $200 per square foot to add an additional bedroom to a house.

Cost of Extension for a Bathroom

Adding a bathroom costs anywhere from $20,000 to $90,000. The average for a 100 square foot, spa-like bathroom is about $75,000. A bathroom addition includes a new roof, flooring, plumbing and fixtures. A spa-like bathroom may include amenities like freestanding tubs, rain shower heads and smart devices. Expect to pay more for these high-end additions.

A bathroom remodel costs between $6,600 and $16,500. It’s significantly less expensive than a bathroom addition since contractors are working with existing space.

A new bathroom adds value to any home, especially when you only have one or two in your home. The amount you’ll recoup depends on where you live. In the West, you can expect an ROI of roughly 67%. In most eastern states, expect an ROI around 47%.

Cost to Build a Master Suite: Bedroom and Bath

Building a master suite costs average $25,000 to $100,000 depending on the extent of the addition. Some upscale work – like custom cabinetry, marble countertops and radiant-heat flooring - can easily take you over $100,000. The size of the addition also increases the cost.

Kitchen Addition Cost

Adding 200 square feet of space onto a kitchen could cost anywhere from $48,000 to $95,000. Kitchen additions may cost more than other room expansions due to the need for plumbing, electrical work and new appliance installation.

Family Room or Living Room Addition

You’ll pay between $17,300 and $43,200 for an 18-foot by 12-foot living room addition. Larger rooms will cost more. Extensive cabinetry, expensive fixtures and premium finishes will add to the price. Consult a professional to get the most accurate estimate for your space.

Bonus Room Over Garage Cost

Adding a bonus room over your garage runs around $115 per square foot. Overall, you can expect to pay about $45,000 on average for this project. You may need to make structural changes to the existing garage to support the bonus room, which will also increase the price.

Other factors that could impact price include:

• A staircase leading up to the second floor
• Premium paint job
• Crown molding
• Cabinetry installation

Laundry Room Addition

A laundry room addition ranges anywhere from $2,000 to $10,000 or more. Most pay between $5,000 and $7,000. Upgrading your appliances, adding a sink and improving storage all add to the final price.

Dining Room

Adding a standard 14 foot by 16 foot dining room costs between $17,920 and $44,800. As the size of the dining room grows, the project cost increases. You’ll pay more for extras like a wet bar, pricey finishes like ebony or sandalwood, and built-in cabinets.

Mudroom Addition Cost

A small, 36 square foot mudroom costs from about $3,600 and $7,200. Mudrooms typically include an easy-to-clean flooring material like tile, as well as plenty of storage options for boots, coats and bags. Some mudrooms double as laundry rooms, but these are typically larger and more expensive.

Cost of a Studio or Apartment Extension

The average cost to add an entire apartment is about $185,500. An apartment addition includes the cost of a kitchen, bathroom and living space. Larger apartments will be more expensive to build. High-end finishes like wood flooring and custom cabinetry will increase the cost.

In-Law Suite Addition Costs

In-law suites are what you make of them, ranging from a simple bedroom to a full detached structure in your yard. It’s important to check with your local municipality, since accessory dwelling units, the technical term for in-law suites, are forbidden in many communities.

• A simple bedroom addition: $44,000
• Full, detached suite: $100,000+

Cost to Build an Apartment Over a Garage

You can expect to pay around $300 or more per square foot to build an apartment over a garage. For an apartment above a 24 by 24 foot two-car garage, you can expect to pay about $175,000 or more. Your choice of fixtures can greatly affect the cost. For example, wood floors will cost more than carpeted floors. The size of the room will also change the price, as larger spaces are more expensive to build.

Detached Additions: Garages and Sheds

• Simple shed-like rooms: $15,000 without electricity or heat.
• Price of a detached garage addition
• Simple units average $9,000-$12,000 with no plumbing, electrical or HVAC..
• Complete units average $18,000 to $20,000 for living space and extra amenities.

Sunrooms, Three- or Four-Season Rooms and Florida Rooms

Average sunrooms cost anywhere from $8,000 to $80,000 or more for a 200-square-foot addition with footings and a slab foundation. The cost of this project depends on the amount of space it adds, the location of the sunroom, extras such as electrical wiring and whether the room needs heat (four-season room) or no heat (three-season room).

Buying a prefabricated sunroom runs around $11,000 per 150 square feet. Once you factor in adding heat, electricity and all the construction costs, it's not unusual to pay between $300 and $400 per square foot for the finished product. If you want to keep the costs low, consider adding the sunroom as a three-season room without heating.

Cost Factors To Expanding Your House

When you’re planning your budget for this project, you need to consider many different factors, including the square footage and the size of the addition. The larger you go, the more expensive the project will be. There are several other necessary services that could impact the cost of your project, including:

• Architectural services: runs between $2,020-$8,390. Ensures that your new addition matches the current style of your home.
• Excavation, demolition and site-preparation: Prepping a construction site costs between $1,300-$5,000. Prices vary depending on the amount of work required.
• Foundation for addition: Expect to pay between $4,200-$13,200 for the job. The cost to build a foundation changes depending on the size of the project and materials used.
• Support beams and roof trusses: Roof trusses cost anywhere from $30-$600 per truss, depending on the material. Support beams cost $1,150-$4,600 to install. Pros can integrate new beams and trusses with the rest of the home’s structure.
• Roofing: Expect to pay $80-$100 per square foot for asphalt shingles and galvanized metal flashing on your addition. Steel roofing costs more, between $75-$350 per square. Slate shingles are between $200-$600 per square.
• Install vinyl siding and trim: Vinyl siding costs about $4 per square foot, and vinyl trim costs between $2-$5 per square foot. These elements give your addition a finished look.
• Drywall ceiling and walls: The cost to install drywall ranges from $1-$3 per square foot.
• Insulation costs about $2 per square foot to install.
• Door installation: The average cost to purchase and install a door is $1,000. Hollow core interior doors are less expensive than heavy exterior doors.
• Adding windows: New windows add light and ventilation to your space and cost at least $235 each. The cost to install windows varies depending on the style, with custom options reaching $2,500 or more.
• Molding for ceilings: The cost to install crown molding runs from $4-$16 per linear foot.
• Electrical wiring: You’ll pay anywhere from $40-$100 per hour to wire your home. Hiring a licensed electrician can help ensure your system is up to code.
• Flooring options: The cost to install flooring is between $1,500-$4,600 depending on the material you choose. Generally, vinyl or linoleum floors are less expensive, while wood flooring costs more.
• HVAC installation: Pros will tie new ducts into your existing HVAC system. The average price for installing ducts and vents is $1,200.

If you're renovating multiple rooms within your current floorplan to make the addition flow more naturally into the rest of the space, visit our home remodel cost calculator to plan your budget.

Will the Addition Add Value to Your Home?

When choosing a home addition, you will want to consider the project’s return on investment. Here are some common improvements and their usual ROI at resale: 

• Sunrooms: 49%
• Bathrooms: 53%
• Master Suites: 63%
• Two-story Addition with upstairs master suite and a downstairs living area: 65%

DIY Room Addition Cost vs. Hiring Contractors

Labor costs make up 30% to 50% of your total budget, depending on the contractor. If you choose to DIY parts of a room addition, you could save quite a bit. Doing your own demolition, for example, can save you more than $500 in labor charges. A handy homeowner may also be able to accomplish projects like laying flooring, painting the walls or installing a new vanity.

However, going it alone means that you’d have to serve as your own manager and subcontract out for plumbing and electrical work. Hiring a pro means having expert knowledge at your fingertips so you can avoid making expensive mistakes.

What to Look for in a Contractor, Construction Manager or Remodeler

Choosing the right contractor is an important step in the process to build an addition. Here are some tips to make sure you hire the best pro for the job:

• Verify that the pros are licensed and insured.
• Check references and ask for pictures of their prior work.
• Ask the pros how long they've been in business and how they screen subcontractors.
• Find out how long they expect the project to take.
• Get estimates from at least two or three contractors to get the most competitive prices.

Agree on Price and Payment Schedules at the Start

Get everything in writing. Agree on a total amount before discussing anything further.

Be prepared for contractors to expect some money in advance, and then again after specific milestones during the course of the project. However, paying too much or too little upfront could put you or your contractor at risk.

No matter how detailed your plan is, remember that things happen. Find out about your contractor's change-order policy in case you change your mind on the colors, fixtures or layout of the room. This is also useful if your contractor runs into problems during construction that require quick decision-making.

Cost of Extension on a Budget

Adding onto a house is an expensive project, but there are ways to shave money off your budget.

1. Remodeling: In some cases you may be able to remodel instead of adding on. Consider finishing the basement (for as little as $11,000) to provide an extra bedroom with a bathroom or a living space. Or improve your existing storage for maximum efficiency. Small adjustments could make an expansion unnecessary.
2. Detached Additions: Other money-saving options include using detached additions instead of attached ones. A prefabricated detached structure could cost less than $20,000, and you could use it as a guesthouse or an office to provide the extra space that you want.
3. Building up also saves money by avoiding excavation costs and the need to pour a new foundation.

Bump-Out Addition Costs

Bump-out prices vary depending on the type and location on the home. It’s smaller and often cheaper addition option. Overall, a bump-out is less expensive than adding a full-sized room, though the cost per square foot is often pricier than that of a larger addition.

FAQs

How much does a mobile home addition cost?

The price of a mobile home addition can vary widely depending on what it added. Additions should not be attached to the home but rather kept completely separate. Examples of common additions include:

• Metal carport costs: $2,100-$4,600
• Storage shed costs: $300-$15,000
• Average cost of a deck: $4,100-$11,500
• Detached garage costs: $17,000-$39,000
• Porch prices: $4,600-$22,000

Always talk to a mobile home contractor before starting any work. There are some special considerations you may need to think about before building. For example, any addition should be able to support its own weight and should not put strain on the existing structure.

Does a Cape Cod addition cost more than other home styles?

Trying to mimic the style of a Cape Cod home can add to the price of your addition, especially if you want it to look authentic. A professional will know the best-looking and most cost-effective way to craft this addition.

Are architects or draftsmen needed for additions?

The cost to hire a draftsperson is between $825 and $2,700. Hiring an architect runs between $2,020 and $8,400. If you’re adding a simple family room onto your home with one door into the rest of the house and one to the outside, a contractor should be able to handle it without the help of an architect. However, if you're moving walls, redesigning the way one room flows into another, or planning other complicated changes to your existing home, you may want to consider bringing an architect on board.

Will an addition look like it was tacked on?

Without the services of a designer or an architect, your addition could like an afterthought or an obvious add-on feature. Skilled designers can create the space you want and deftly tie it into the existing structure so that it looks like it was always there.

Do I need to worry about restrictions?

Always check with your local government to research zoning restrictions. In some areas, you may not be able to build within a certain number of feet of the front, sides or rear of the property lines. Other areas have rules about how much space on your property can be covered with buildings, how close you can get to protected spaces such as wetlands or how high you can build up.

What should my first step be?

Create a plan for your new room, find a contractor to do the work and get all the necessary permits. This kind of a major project requires local permits to make sure everything is in-line with building codes.