House Addition Calculator – Get Home Addition Costs

Typical Cost To Build an Addition
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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?

Cost to Build a Home Addition
$32,580 - $91,300
See costs in your area Start Here - Enter Your Zip Code

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.

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.

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.

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

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.

Cost to Build a Home Addition
$32,580 - $91,300
See costs in your area Start Here - Enter Your Zip Code

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%

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.

Cost to Build a Home Addition
$32,580 - $91,300
See costs in your area Start Here - Enter Your Zip Code

About Leo Bender

Leo has been a contractor since 2003, specializing in: roofing, siding, general contracting (GC) and residential remodeling. Leo is also a Certified HVAC, Oil & Gas Heating Technician/Installer. In addition to roofing and remodeling, Leo is passionate about Solar, green building and energy conservation, so a lot of my time and energy goes to installing energy efficient heating and cooling systems.

See more about Remodeling Calculator team here

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11 comments on “House Addition Calculator – Get Home Addition Costs

  1. greg ballard

    Your 100% correct , My customers dont have a problem with the cost, , It seems that they brag about cost not savings . I dont think they have clue about quality . The main complaint that a kitchen remodel takes longer than a week end, or that I’m behind schedule even though they have made numerous additional things to the original schedule. I blame home renovation tv shows.

  2. Carl

    I live in Colorado…. Our home prices have jumped to top of the nation… and three local contractors quoted be between $80-$120/sqft…….

  3. Never Noe

    Mr. Leo is right. Most people don’t consider or even know all the variables that go into the cost of construction projects. I, personally, like your fancy calculator sure it’s not exact for everything everywhere due to those pesky variables…but it’s a great tool to use as a general idea of the potential costs.
    Thank you very much for inventing it.

    1. Leo B Post author


      Thank you for the input. It is difficult to convey such message – folks don’t consider what’s behind the scene, and only see a number.

      I have a great example from another field – HVAC … There are tons of ads on Craigslist and Facebook marketplace, of Mini Split Heat Pump installers doing the job (without materials) for something like $750-900. And these “professionals” post their work pictures. It scares me.

      They show how they coil up the copper line-set (refrigerant lines). Homeowners do not understand that coiling up lineset is a death sentence for their Heat Pump.

      It’s an oil trap, and once oil is trapped in the lineset, it restricts the free flow of refrigerant, which greatly reduces efficiency. But what’s much worse – this oil is for lubrication and cooling the compressor. If compressor is starved of oil, it will overheat, and burn out! This is just one sign of an overall unprofessional “installer”.

      Here is an example (just got this off FB – lineset coiled 3 times – look behind compressor): Bad Heat Pump Job - lineset oil trap

      And so many unsuspecting homeowners fall for this sub-par work, merely because they are attracted by $750 price and don’t want to pay a market rate.

      Later they are convinced of what a great deal they got, and refer their friends and family…

      And then real professionals need to come in and get the “blame” because the unit is for real dead.

      Anyway … I understand that everyone wants to pay less … but some things just cost more, and paying less = bad work. Not saying that paying more always means good work – far from it… but odds of the work being better when you pay more, are higher…

      Cheers, Leo

  4. Timothy L Deese

    Hey man I’m just looking at your message you put on here and I’m a contractor myself and I’ll tell you homeowners have no clue how much goes into doing an addition and the money you got to spend to do it and they think you’re supposed to make no money they think that you’re supposed to do it basically for free and I tell you I’ve done a couple of additions and I swear I never seen no money if anything I lost money so I no longer take additions unless I get paid the going rate because you can’t cut yourself short in this business

    1. Leo B Post author


      Try to get a quote for local builders / contractors, to see the “non Central Park” addition costs. You must really not understand the amount of materials and labor that goes into building an addition, and on top of that contractor needs to make profit, and cover overheads (insurance, taxes, advertising, bookkeeping, office, etc).

      If addition is on the ground, you need to pay excavators, concrete pourers, and then a standard framer, electrician, roofer, plasterer, flooring and painters, etc. Also include architects/engineers, building permits… its not as simple as building a shed from 2x4s and OSB, on cinder-blocks.

      If anything, our quotes might be on the low side of things.

  5. Soppheap Thong

    plan to add a story with 4 bedrooms, 2 baths and family room on the top of 1471 sq.ft house. how much is total cost?

    In Garden Grove, California, does it required 3 cars garage for more than 5 bedrooms house ?

  6. Garry

    Thanks for a realistic price reality. Been doing this for years and still scratch my head pricing additions. Cost of living is like a mirage .