How Much Does a Home Addition Cost?

If you feel like you do not have enough space in your current home but love everything else about it, adding an addition makes your property exactly what you want. Additions come in many shapes and sizes, from tiny bump-outs to full second stories.

For this reason, there is a large range of costs associated with building an addition. The national range is $20,000 - $100,000 with most people spending around $55,000 on a 240 sq.ft. addition on the first floor.

Home Addition Costs

Cost to Design a Home Addition

Do not overlook the designing aspect of the addition because it is an important step. Your addition must match the details of your home inside and out to be seamless and to get the most value. Designing also makes the most of the space, so more is done with less square footage.

The general rule of thumb when it comes to the cost of designing a home addition is for the designs to cost between 10% and 17% of the final costs. So, for a 240 sq.ft addition costing $55,000, you pay between $5,500 and $9,350. This varies, depending on the designer and detail of the plans.

Home Addition Cost per Square Foot

There is a range of associated costs per square foot ¹ for a home addition, depending on the room’s use, how much existing space is used, and where the addition is built. In general, expect to pay roughly $200 a square foot for a finished addition. Some complex projects may cost more, while very simple ones may cost less. Based on this figure, the following spaces have these costs:

Room Addition Costs by Size

The size of the room you add has an impact on its total cost, with larger spaces costing more than smaller ones. Keep in mind different types of rooms have varying costs regardless of size. The following room sizes have these costs on average:

Home Extension Cost by Type of Room

The room type you add impacts the total project cost as well. Closets, cabinets, plumbing, flooring, and other details make the space more or less expensive than the average cost. Below are some of the average prices for building different rooms based on the most common sizes for each space.

Laundry Room Addition Cost

The average laundry room is only around 35 square feet, making this more of a bump out than a full addition. Laundry rooms need to be waterproof and usually include cabinetry or storage along with the appliances. This means the costs stay relatively low at around $7,000.

Mudroom Addition Cost

A mudroom addition is usually around 50 square feet, so even with the included cubbies and organizational material needed, it costs around $12,000. The average mudroom includes cabinets, storage, and a durable flooring, such as porcelain or slate ², in the price.

Sunroom Addition Cost

The sunroom takes on several different forms and building styles. Sunrooms have windows or screens or full walls, depending on your goals. They cost an average of $45,000 for a three-season room.

Attic Addition Cost

While it is called an attic addition, this is an attic conversion. It is still a relatively large project with an average cost of $47,000. This includes making sure there is an egress like stairs and working with the lower ceilings, so you may have less space than you imagine with this type of addition.

Bathroom Addition Cost

A full bathroom addition of 48 square feet in a new space costs around $47,000. While this is a small space, it has extra needs for plumbing, raising the costs. Bathroom additions include everything from the shower to the sink and toilet, along with tile and accessories.

Family Room Addition Cost

The family room comes in many shapes and sizes and is finished in numerous ways. Family rooms are usually informal and made for the family, so they include storage, entertainment areas, and space to spread out. They have an average cost of around $54,000.

Living Room Addition Cost

The living room is often smaller but more formal than the family room. So while there is less space, it is more likely to have higher-end materials like exotic hardwood ³ or marble floors and nicer features and moldings. Living room additions cost around $54,000.

Bedroom Addition Cost

Bedroom additions may be slightly smaller, but they have additional needs for closets, which raise the cost slightly. Closets, storage, and the necessary lighting drive up the costs closer to an average of $57,000, despite the smaller size.

Kitchen Addition Cost

Kitchen additions often have added costs for cabinetry and plumbing, so while the average size of the kitchen falls between 100 and 200 square feet, the cost averages around $60,000. The average kitchen addition includes flooring, cabinets, counters, appliances, and framing and finishing, driving most of the total cost.

Home Theater Addition Cost

Adding a home theater brings fun and entertainment to your home. They may be added to basements or existing spaces or built onto your home if you do not have the space. Because of the need for acoustic materials and equipment costs, it averages $87,000.

Home Extension Cost by Type

There are many other ways to add to your home to expand your living space, and not all create complete rooms. Each has an associated cost:

Bump Out Addition Cost

A bump out is a small extension of an existing room. It adds square footage but at a much lower cost. Because this is not a full room, the costs are considerably lower at around $5,000.

Dormer Addition Cost

A dormer is a roof extension with a window. It adds extra space to a low-ceilinged room like an attic space. Adding a dormer costs around $5,000.

Balcony Addition Cost

A balcony is a small deck suspended off the side of the home. This is usually a short and simple project costing around $5,000 on average.

Greenhouse Addition Cost

If you do a lot of gardening, add a greenhouse to your property. This project has an average cost of around $16,500.

Cantilever Addition Cost

If you want to add a room to the second floor of a home, extend the space by cantilevering it out over the lower floor. These spaces are not big, but the added support increases costs, averaging around $20,000.

Porch Addition Cost

Adding a porch boosts your home’s curb appeal and value while adding outdoor living space. The average cost to add a porch is $21,440.

Modular Room Addition Cost

Modular building is less expensive than traditional because the room is factory-built, delivered, and added onto your existing home. The cost per square foot is lower, and the timeline is faster. Modular room additions cost $25,000 on average.

Garage Addition Cost

Having an attached garage improves your home’s value and improves overall function as well. The average cost to add a garage is around $35,000.

In-Law Addition Cost

An in-law is a fully fitted small building or apartment that is either attached or detached from the rest of your home. Because they often contain kitchens and baths, their costs are higher at around $80,000 on average.

Cost to Add a Second Story

Second story additions have much higher costs than adding a room on the ground level ⁴ of your home. They involve removing your roof and attic, adding a new floor, walls, and roof for several rooms. This often makes the cost per square foot between $300 and $500, and it is common for the total addition cost to reach $150,000 to $200,000 for homes that are 1,000 sq.ft. or larger. For smaller homes, it costs $90,000 to $120,000.

Cost of Adding a Basement to an Existing Home

To add a basement to an existing home, you must give it a new foundation, which means lifting your home, excavating the area, and pouring a new foundation. This has a range of costs, depending on how high the house needs to be lifted and how big the basement is. Expect costs to be at least $50,000 for this project. They may be much higher, depending on factors like your location, soil, and house size.

Home Addition Cost Breakdown

While every project is different, most have several factors in common that give an idea of where your costs are going during an addition.

Keep in mind that this is a general range that nearly all additions include. Specialty rooms like kitchens have additional costs.

Labor Costs to Build an Addition

The labor portion of your project is dictated largely by which professionals you use and in what capacities. In many cases, you hire a builder or general contractor, and they subcontract out the various specialties, so you are not paying each pro directly. Expect to pay the following rates:

Architect - $150 - $400/hour

Electrician - $65 - $85/hour

Roofer - $2 - $3/sq.ft.

Siding Contractor - $40 - $50/hour

Carpenter - $70/hour

HVAC technician - $50 - $100/hour

Framing professionals - $4 - $10/sq.ft.

Painters - $50/hour

Flooring installers - $1 - $5/sq.ft.

Drywall installers - $1 - $3/sq.ft.

General contractor - $150/hour

You may also need a plumber at $45 - $200/hour if your addition is a kitchen or bathroom.

Factors that Affect the Cost of Expanding Your House

Every project is different, and many factors impact the cost of your addition. These include the materials used, finishing choices, labor costs in your area, addition size and placement, how you heat and cool the addition, amount of design, and prep work entailed. Any special extras like built-in ⁵ cabinets or shelves all impact the final addition cost.

Cost to Draft a Home Addition

Most home additions need a set of blueprints, just like any other major build. A draftsperson works with an architect or builder to produce these. They have an average cost of around $1,200.

Cost of Framing an Addition

Your addition is framed in the same manner and materials as the rest of your home. This provides structure for the space and is integral to the project. Framing has an average cost of around $2,500 for a new addition.

Enhancement and Improvement Costs

HVAC

In some cases, you may extend things like ducts into your new addition, but in other cases, this stresses your current system too much. It may be a better choice to heat and cool your addition separately. Things like ductless heat pumps are good for additions because they do not tie into your existing system. The cost for a single-zone system is just over $2,000.

Post-Construction Cleaning

Additions are very messy both in the new area and in your existing space. Post-construction cleaning makes your space livable faster. This has an average cost of around $550.

Interior Designer

An interior designer is often helpful when adding a new space because they help you see the possibilities and help furnish it. The average cost of hiring an interior designer for one room in the home is around $5,500.

Additional Considerations and Costs

• Additions add value to your home, but keep in mind that this value is likely not equal to the cost. Additions add the most value when they keep the design of the rest of the home.
• Make sure you get your contract in writing, including the total amount and the breakdown of materials and details. Include a lien release in the contract for protection.
• Sometimes, remodeling instead of adding on gains space. For example, you may remodel a basement to gain extra space often for less.
• Mobile homes also have additions, but these must be considered separate structures from the rest of the building and have its own foundation. This costs around $150 - $300 a square foot.
• Have your contractor obtain the permits needed for the addition. They often know tricks that help speed the process.
• Make sure the area you are building onto is accessible both inside and out. This means removing landscaping and moving furniture and window coverings in most cases.
• You may do your own demolition, tearing down the walls and hauling away the debris, to save money.
• The average timeline to build a new home addition is between 2 and 3 months from start to finish.
• Before ordering new material, check with your contractor to see if they have any leftover material used. This may save you money. Using stock sizes instead of custom also helps reduce costs.
• You will likely need to compromise on this project in some way, whether on the size, materials, or timeline to meet your budget. It is fine to start with your ideal project, but then try to cut back.
• Keep resale in mind when you add to your home. Make sure the addition fits the rest of your home and neighborhood to ensure it appeals to buyers.

Remodeling Terms Cheat Sheet

¹ Foot: A support for the foundation of a house that also helps prevent settling. It is typically made of concrete reinforced with rebar, but can also be made of masonry or brick. It is usually built under a heavier part of the house like a wall or column, to distribute the weight of the house over a larger area.

² Slate: A fine-grained rock, typically bluish-gray in color, that can easily be split into thin layers and is commonly used as a roofing material

³ Exotic hardwood: Timber from deciduous, flowering, seed-bearing trees that grow in tropical rainforests

⁵ Built-in: An item of furniture, such as a bookcase or set of cabinets, that is built directly into the structure of the room. Built-ins are therefore customized to the room and not detachable

⁶ Blueprints: A technical drawing of an architectural design. Traditionally these were made using a printing process that produced a white line on a blue background. They can also be made with CAD software and a large-scale printer