House Addition Calculator – Get Home Addition Costs (2023)

While expensive, building a home addition is a highly rewarding undertaking. After all, you will have the desired extra space, without having to buy a larger house.

Popular house additions include: an extra bedroom, bathroom, kitchen, office space, entertainment room, etc.

Here is an updated list of popular house additions and their costs to help you plan your budget.

To get started on building your home addition contact your local building pros for FREE ESTIMATES!.

How Much Does An Addition Cost?

The average cost to build a small to medium size single room home addition is $35,000-60,000.

However, because house additions come in a wide range of shapes and sizes, the construction costs vary greatly.

The cost of large house addition that includes a kitchen or bathroom is comparable to building a small home. Average prices start at $90,000 and can go up to $160,000

Keep in mind that the cost of a large second floor addition can cost as much as 50-70% more compared to the cost of the same size first floor addition. Prices for second floor additions of 1,500 sq.ft. start at $150,000 and can go all the way up to $400,000+

If you are planning a complex project, such as a two-floor addition, you will need to hire an architect and budget for his fees. These can be as much as 5-7% of the total cost.

Some people save money by hiring a design-and build firm, that has a staff architect and includes the design fees into the final price.

Expect to spend $1,200-2,500+ on blueprints and $2,000-5,000+ on architectural design.

Addition Cost Per Square Foot

On average, addition cost per square foot is $125-400. Obviously, the addition’s size and location will be the primary cost drivers, but the following factors may increase the final price as well:

– complexity of architectural design
– quality of building materials and finishes
– permits and inspections
– unexpected plumbing, HVAC or electric issues

To be on the safe side and avoid running out of funds, its best to budget 15-20% of the total cost for unforeseen expenses.

Room Addition Cost

Here is what you can expect to pay to add on different types of rooms to your existing home.

(Video) Instant Bathroom Addition Cost Estimate from Bathroom Remodeling Cost Calculator

This estimate includes: new foundation, roof, siding, proper wall insulation, new windows, flooring, electric, HVAC and finishing work.

  • Typical bathroom addition cost: $25,000-40,000 for a 5×8 room with a tub or shower enclosure.
  • A spa-like, master bathroom addition cost: $80,000+
  • An average size kitchen addition without bells and whistles: $25,000-50,000
  • Upscale kitchen with custom cabinetry and high-end appliances: $100,000+
  • 10×15 bedroom (without a bathroom): $20,000-35,000
  • Room addition cost (400 sq.ft.): $30,000-100,000
  • First floor addition with multiple rooms (800-1,500 sq.ft): $150,000 +
  • Second floor addition with multiple rooms (1,500 sq.ft.): $200,000-475,000
  • Sun room or three/four season room without heat (250 sq.ft.) $30,000-55,000

While these prices may seem extremely high and out of your budget, you can pay for the addition by getting a home equity loan.

In fact, that is what the majority of homeowners do. Another financing option is to get a construction loan.

The key to setting a reasonable budget and sticking to it is to identify and manage all the anticipated remodel costs in the beginning stages of the project.

House Addition Cost By Room Size

The larger the size of the space you are looking to build, the less you will be paying per square foot.

Here are popular addition room sizes and their price estimates:

20 x 20 room addition costs $50,000-100,000

12 x 12 room addition costs $18,000 – 36,000

10 x 12 room addition costs $15,000 – 30,000

Overall, 20×20 room additions that include either a bathroom or a kitchen are most popular. This is because adding a small room does not provide much extra functionality or value to the home.

Moreover, additions that have a bathroom are a lot more popular than bedroom or office additions, because it is always helpful to have an extra bathroom in the house.

How Much Does It Cost To Add A Bathroom?

Among all room addition types, a bathroom is the most desirable upgrade that also boasts one of the highest ROI’s.

Because plumbing work is a necessary component of building a bathroom addition, the overall cost is higher, compared to adding a simple room. An average size bathroom addition (5×8) costs $25,000 – 40,000.

Overall, prices for a bathroom addition start at around $450-500 per square foot, compared to an average of $200 per sq.ft. for a regular room. A high-end luxury bathroom addition costs as much as $700-850 per square foot.

There are also increased labor costs in having to install all the bathroom fixtures, tile the floor/walls, put in cabinetry/shelving.

Moreover, there is a very wide price range when it comes to bathroom fixtures, themselves. For example you can install a standard toilet by American Standard from Home Depot for $200, or a TOTO toilet for $1,500.

(Video) DIY addition. How to build a room addition to your home on a budget.

If heating your bathroom addition is a challenge as its too expensive to extend the main source of heat into the addition, consider installing a mini split heat pump and radiant heated flooring.

Curb Appeal Of A Home Addition

When designing a home addition, whether its its just a sun room or a two-storie master suite or an in-law apartment, its important to consider how the addition will look attached to the main home.

The last thing you want is for the addition to seem like it was hastily tacked on to the house and now it sticks out like a sore thumb.

Ideally, an addition should look like an organic extension of the house, where the flow from the old space to the new feels very natural. This requires professional architectural planning and design.

Its also important to carefully select your siding and roofing materials, so that they match and complement the siding and roof of your original home.

While you may not care what your addition looks like on the outside, this may become a stumbling block if you ever decide to sell your home.

Prospective buyers will love the expanded foot print of your house, but they may have a major problem if the addition really looks out of place.

A new design trend that has been growing in popularity is to build a modern addition together with a classic architectural style home.

Modern additions usually have flat roofs, oversized windows and make use of engineered wood or fiber cement siding materials.

Building A Second Story vs Ground Floor Addition

Many homeowners who are looking to save money on the cost of an addition wonder if its cheaper to build up (add rooms to the second or third floor of the house) or to build out?

Before you consider the cost of these two addition types, you need to first find out your zoning laws and what you would actually be allowed to build.

Ask your town inspector to come in and guide you. In some cases you may only have one option available to you, so that will spare you the headache of making a decision.

In terms of building costs, its considered to be overall cheaper to build up rather than out. This is because building a ground floor addition requires excavation and building a foundation, which dramatically increase your total cost.

However, when building up, you have to first make sure that the house structure can support the new addition. If it cannot and you have to reinforce it, the cost becomes similar or even higher compared to building a ground floor addition.

If you are trying hard to save money and don’t need a lot of extra space, consider bumping out, or building a shed dormer addition. This will not require you to change the foot print of your home, and can be done using the existing house and roof structure. Many small bathroom additions are built as shed dormers.

The cost of a large shed dormer that can fit a bathroom can be $25,000-30,000. This is significantly cheaper than building an addition.

(Video) How To Attach Home Addition Roof Framing To Existing Sloping Roof

Is It Better To Build Up Or Out?

Aside from the cost there are other factors that you need to consider, when deciding whether to build up or out:

Purpose of the addition

If you are looking to add a bedroom, an office or a bathroom, it is reasonable to do this on the second floor.

However, if you want to expand the kitchen, or add an entertainment room, it makes sense to build these on the ground floor.

Moreover, building an in law apartment is also often more convenient as a ground floor as opposed to a second floor addition.

For someone who is looking to add extra space, such as a guest room, office, play room, man cave, etc finishing your attic or basement may be the easiest and cheapest way to achieve this goal.

No major, expensive construction required!

You can remodel and finish your attic for $12,000-20,000, and get a very nice addition to your house space without breaking your bank.

Home value

Your addition should add to the value of your home, and the best way to do this is with increased functionality and convenience.

As a rule of thumb ground floor additions are considered more convenient, as many people (especially older ones) don’t want to bother walking up and down the stairs.

However, this can also be market specific, so its best to consult with your local realtor and get some hard data as to which types of house additions are more popular in your area.

Will you be sacrificing valuable backyard space?

Some homes don’t come with huge lots of land, and building a ground addition may mean that you will be left with a very small backyard.

If this is an undesirable, as you use your backyard for kid’s play and to entertain guests, perhaps you have a portable pool, etc, it may make sense to build a second floor addition.

4. Convenience during the construction phase

(Video) How to Estimate the Needed Number of Studs and Cost | Material Estimator

If you plan on building a second story addition, you have to be ok with a prolonged disruption to your house routines as well as noise. You may also need to move out of your house for the duration of the construction. Plan ahead and see if this is feasible for your family.

Factors That Drive Up Home Addition Costs

There are a number of factors that may significantly increase the total cost of an addition.

For example, if you are adding a new bathroom or a kitchen, you will need to install an entirely new plumbing system.

This will cost thousands of dollars. One way to save money on this is to connect to the existing plumbing system, if the addition design allows for it.

Another significant expenditure is hiring a mason to pour a level concrete floor, if you are planning to build a garage.

You should also budget at least $1,500-4,000+ extra to fix the landscaping around the new addition.

You will need to pull building permits for most of the construction and remodeling jobs. Each permit will be a few hundred dollars. Also, you may need to run special kinds of tests, such as soil testing, which may cost $1,000+

Keep in mind that if you do not hire a General Contractor to oversee the project and hire subcontractors, you will need to hire these pros yourself to complete specialized tasks. They may include a roofer, electrician, plumber, window installer, etc.

Lastly, the quality of materials you select will also make a great difference in the final cost.

Choosing custom, brand name, or luxury building materials can significantly drive up construction costs. Here, you need to carefully consider your total budget and what you are planning to achieve.

Sometimes, going for more expensive materials is justified because of their improved longevity and durability, as opposed to spending a lot more money just to have an upscale look.

For example installing a metal roof instead of asphalt shingles may cost $10,000-15,000 more, but will offer superior weather protection for the lifetime of your house.

ROI Of A House Addition

Because a house addition is such a major remodel that also costs tens of thousands of dollars, its important to consider your return on investment before you jump into it.

In general a room addition, whether second floor or attached has an ROI of about 40-50% Large room additions that have a bathroom have a much higher ROI of about 60%.

Homeowners can get the best returns by building a multi room addition with a bathroom that has a separate entrance, such as an in-law apartment or a suite. You can expect the ROI to be about 85-95%

(Video) Easily Estimate Your Cost to Build

Keep in mind that high-end and luxury remodels do not have a high return on investment. So if you want to splurge for your personal enjoyment and install expensive finishes, fixtures and accessories, go for it!

However, don’t expect to get more than 20-25% of your investment if you put your house up for sale.


How do I estimate the cost of a home addition? ›

The bigger the space, the higher the price. According to HomeAdvisor, home additions cost $80 to $200 per square foot. Adding a spare room is a common project, and the average cost ranges from $32,000 to $80,000 for a 20-foot by 20-foot room, with the higher end including more customization or luxury fixtures.

How much does it cost to add 1000 square feet to a house? ›

How much does it cost to add 1000 square feet to a house? Based on a cost of $80 and $200 per square foot (£627 and £1,567 per square metre), you can expect to pay between $80,000 and $200,000 (£58,244 and £145,589) to add 1000 square feet to a house.

How much does a 10x12 addition cost? ›

A 10x12 room equals 120 square feet, multiplied by $125, yields a total estimate of $15,000. In most cases, that amount above will likely be in the ballpark of where the actual cost will fall for most room additions are most likely the same as new construction.

How much does a bump out cost estimator? ›

The cost to build a bump-out addition can vary drastically, and is dependent on a variety of factors including size and design. With that in mind, if you're considering building a bump-out addition, expect to send anywhere from $4,000 to $30,000.

What is the cheapest home addition? ›

Finishing a basement, attic, or garage is one of the more inexpensive ways to add a room to your home as you won't need to add a foundation, roof, or structural elements.

How much does it cost to add a bedroom and bathroom to a house? ›

The cost of adding a master bedroom and bathroom to your home can vary. Most homeowners spend around $62,500 on this project, but the cost of this addition can range from as low as $25,000 to as high as $100,000.

Is it cheaper to build or add on? ›

It is typically cheaper to build an addition than to buy or build a new home that equals the space of your existing house plus an addition. At the very least, the closing costs involved with selling your old house and buying the new house would push this option over the top.

Is it cheaper to add on or build up? ›

The reason building out is typically cheaper is because building upward requires more labor, more materials, several permits, as well as the help of a structural engineer.

Is it cheaper to build up or out on an existing house? ›

The Cost of Remodeling a Home vs.

According to The Spruce, an average rebuild costs twenty percent more than remodeling an existing structure. If cost isn't an issue, building a new home allows you virtually any option for your home's structure, layout, ceiling height, and square footage that your lot allows.

What is the average cost of a 12x12 room addition? ›

The average cost to build a 12×12 room is $18,432 at $128 per square foot.

How big is a 20x20 room? ›

How many square feet is a 20x20 room? The square footage of a room 20 feet wide and 20 feet long is 400 square feet. The square footage is found by multiplying the width (20 ft) by the length (20 ft).

What is the cheapest way to add square footage to a house? ›

Finish an Attic

Take advantage of an unfinished attic to add livable square footage to your home—often the most cost-effective way to gain valuable space.

How big can a bump out be without a foundation? ›

As small as 2 feet: Bump outs may extend as far as 10 to 15 feet from the house, but they can also be tiny pop-outs that are no deeper than 2 feet. Cantilevers: Small bump outs often are cantilevered (unsupported by posts) from the house. This is typically limited to about 2 feet in depth.

How much does it cost to push a wall out? ›

If you're ready to add some extra space, the cost of a bump-out in 2021 ranges from $4,000 to $30,000.

What are build out costs? ›

Build-out Costs means, in respect of either Project, the Construction Costs in respect of such Project and includes, without limitation, all financing or debt service costs (inclusive of interest and fees, whether paid, accrued or deferred) associated with any financing of the foregoing.

How do I lower the cost of an addition? ›

Home Addition Cost Saving Ideas
  1. Cost saving Idea 1: Involve a Home Builder or General Contractor in the design phase. ...
  2. Cost saving Idea #2: Top-up versus extension. ...
  3. Cost saving Idea #3: Keep existing brick cladding for main level intact and Exterior finishes. ...
  4. Cost Saving Idea #4: Basement refinishing and Renovations.
Jan 12, 2023

How much do additions cost in 2022? ›

Adding a room, either as a bedroom or a living room, is the most common home addition cost. The average home addition cost of a 20×20 home addition will fall somewhere between $80 – $200 per square foot. This means that the average home addition cost will be anywhere from $32,000 – $80,000 per square foot.

Can you add an addition without foundation? ›

Unless you're building up or bumping out, every addition requires some sort of masonry foundation dug down below the frost line so it won't get pushed around by freezing temperatures.

What adds more value to a home bedroom or bathroom? ›

According to Opendoor's data, adding a full bathroom can increase the median home value by 5.7% on average, which is a dollar increase of about $17,638. We define adding a full bathroom as converting existing space to include a shower, sink, and toilet.

Does adding a bedroom and bathroom increase home value? ›

More often than not, adding a bedroom increases the value of a home for when you sell. For every bedroom that's added to a home, expect the price of a home to go up between $30,000 and $50,000.

How much value does adding a full bathroom? ›

In general, a bathroom can increase your home's value anywhere from 10-40% depending on the quality of the bathroom and its updates.

What adds most value to a house? ›

Projects That Boost Your Home's Value
  • Remodel the kitchen. Updates to the kitchen pay off. ...
  • Upgrade the appliances. ...
  • Boost the bathrooms. ...
  • Remodel the attic or basement. ...
  • Get decked out. ...
  • Boost curb appeal. ...
  • Improve energy efficiency.

How to design a home addition? ›

4 Helpful Tips for Designing Your Dream Home Addition
  1. Consider Why You Want More Space. You love the neighborhood and the location of your home, but your house is getting a bit cramped. ...
  2. Check for Obstacles and Zoning Regulations. ...
  3. Choose the Style. ...
  4. Create the Plans.
Oct 5, 2021

Is adding a second floor worth it? ›

Adding a second story will not only increase your home's space, but it may also increase its resale value. If you have the market in mind, it's always a good idea to check with a realtor to ensure that your investment will likely translate into a higher resale price.

How much does it cost to add 300 square feet to a house? ›

So, for example, if you got a permit to add 300 square feet of additional living space that investment is roughly around $60,000 before any final features are added to your new room.


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