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How Much Does It Cost to Add a Room to a House

You need an extra room in your house. Well, your budget is going to be one of the first concerns. Your expansion plans will have to be tailored to your budget. 

How much does it cost to add a room to a house?

It depends. Various factors come into play. On average, an expansion project would cost $47,500.  However, this is not a fixed rate. Factors such as the nature of expansion, materials required and placement, etc. determine the price. Whether or not professionals are hired also factors into the cost of the project. 

This provides you with a guideline on what you’ll need to consider. However, you should keep reading for a complete and comprehensive breakdown of the project cost.

Let’s get to it!

Cost to Add Room to a House

Getting an idea of the total cost of adding a room to a house is tough. There’s actually no fixed figure. Your cost will change based on what materials you use, where you build, and more.

Here’s a neat way you can calculate the cost:

Cost HeadLow Mid High
Architect $2,000$5,200$8,400
General Contractor$14,400$25,200$43,200
Building Permit$300$1,200$2,000
Foundation $4 per sq. ft$13 per sq. ft$25 per sq.ft
Electrical$2 per sq.ft$4 per sq.ft$7 per sq.ft
Drywall $1 per sq.ft$2 per sq.ft$5 per sq.ft
Insulation$2 per sq.ft$6 per sq.ft$8 per sq.ft
Paint$2 per sq.ft$4 per sq.ft$6 per sq.ft
Vinyl$3.5 per sq.ft$7 per sq.ft$15 per sq.ft
Linoleum $5 per sq.ft$9 per sq.ft$15 per sq.ft
Wood$14 per sq.ft$23 per sq.ft$32 per sq.ft
Carpet$7 per sq.ft$10 per sq.ft$12 per sq.ft
Tile$15 per sq.ft$17 per sq.ft$20 per sq.ft
Site Prep
Load bearing wall       $1,200$3,400$10,000
Non LB wall$300$700$1,000
Foundation  Installation$4,000$6,000$12,000

Breaking Down the Costs

You now have a clear concept of the cost heads, we can start exploring. Going over the costs in more detail will help you understand what you’ll need.

Hiring Professionals

We start here as you’ll first need to decide whether you DIY it or hire professionals. If you decide to complete the project on your own you can greatly reduce the cost. But that isn’t advisable, as you’ll need to be skilled in a lot of things.

DIY-ing the room addition means you’ll need to do your own plumbing, wiring, and woodwork. Not to mention, you’ll need to prep the site for expansion and demolish any walls too. All of this makes the project quite complicated. 

So if you want a good result and make good time, we’d suggest you hire professionals. Okay then, what professionals would you need and why?


You’d need an architect for drawing up the expansion plans. This is what you’ll need to submit for getting the building permit. Architects can charge anywhere from $2,000 – $8,400 for a home addition. 

This price will be well justified as well. Since hiring a professional would mean that your expansion matches your house, it’ll be worth it. 

General Contractor

The next thing you’d need is a general contractor. A general contractor will oversee the entire project, and carry out most of the construction work. On average a general contractor would charge you $100 – $300 per hour

Considering a 400 sq. ft. addition takes 3 weeks on average, expect to pay $14,000. That’s for a budget contractor. Higher-end contractors will run you almost $44,000

However, there’s an advantage here. Let’s say your addition doesn’t require any complex electrical work or plumbing. In that case, all you need is a general contractor. The simple wiring required for putting in outlets can be carried out by general contractors. 


Before getting to hiring an electrician you should consider whether there’s a need for an electrician. Simple outlet installations can be completed by the general contractor. And you can also DIY the rewiring.

However, it’s suggested that you hire an electrician for complicated rewiring jobs.

A good electrician will charge you just to walk into the place. But it’ll be well worth the hassle. Working with electricity can be very unsafe. You’d need to follow a ton of safety protocols to make sure you’re doing it safely.

Completing all electrical work is not the same as putting in new outlets for microwaves. It will get messy and complicated. The end result might turn out aesthetically displeasing or worse non-functional. So, it’s best to bite the bullet and get a professional. 

At the very least an electrician would charge you $50 for every hour on the job. This could even go as high as $300 an hour depending on the job complexity. It’s best to not cheap out on electrical work. 

An electrician would take 2 – 4 days to rewire for a typical 400 sq. ft. home addition. Considering an 8-hour workday, the cost would amount to $800 – $1,600. For a higher-end electrician, you’d be spending anywhere from $4,800 to $9,600.     

The cost would increase based on the size of the addition. Keep in mind this is just the cost of labor. The cost of materials for electrical work will be considered separately. 


They charge by the hour as well. A plumber would charge $95 an hour on the low end. A top-of-the-line plumbing job could run you almost $900 an hour. But, you’ll most likely only need new plumbing if you’re adding a kitchen or a bathroom.

A mid-tier plumber would charge $400 – $500 per hour. However, that will pay off as money is saved on plumbing jobs for leaky showers. If you’re not adding a bathroom or extending the kitchen you can strike off plumbing costs. 

On average a new plumbing job would take 3-5 days. Let’s consider an 8-hour workday. That would bring the plumbing cost up to $2,280 – $3,800 on the low end. Top-tier plumbers would cost you $20,000 – $36,000


And lastly you can look into hiring a carpenter. This is an optional expense. The general contractor will complete most if not all of the woodwork. You can still get a carpenter to make any aesthetic additions to the room. 

A carpenter would charge anywhere from $75 – $230. But this is an expense you can do without. 

Site Prep Cost

You’ve already considered the cost of hiring professionals. Now, you need to consider the cost of preparing the site. 


You’ll only need to excavate if you’re building on the first floor. If you’re just extending a room or building up or under, you won’t need to excavate. 

Excavation can cost anywhere from $1,140 – $5,000. On average, for a building with a 400 sq. ft. addition, you’d pay $2,300 for excavation. This is one of the costs you can strike off based on where you’re building. 

If it’s a bump-out or a 2nd-floor expansion or basement room, excavation won’t be required. 


This one’s also an “if” expense. It won’t be necessary when building up or under. The cost of demolition will differ based on the type of wall. 

If you’re removing a load-bearing wall, it’ll cost you $1,200 – $8,000. For a non-load-bearing wall, the demolition cost will range from $300 to $1,000. It’s best to get an expert to demolish the walls. If done incorrectly, it can risk the integrity of the house. 

Foundation Installation

Again, you’ll only need to bear this expense if you’re building on the first floor. The cost of installing the foundation will range from $4,000 to $10,000. This price takes into account the type of foundation being installed. 

For example, for a crawl space foundation, you’d pay $7 per sq. ft. Or, around $8,000 for a 400 sq. ft. addition. Similarly, other types of foundations will cost differently.

Material Cost

Once you have site prep and professional hiring covered, you’ll need to budget for materials. You also need to decide if you want to build it with EIFS or Stucco. To help simplify the process for you, we’ll be breaking the costs down. 

Foundation Materials

You’ll only need to expand the foundation if you’re building out. That is if your home addition is on the first floor. In any other case, you can skip this. 

The cost of foundation materials ranges from $4 to $25 per sq. ft. For a 400 sq. ft. home addition, you’d need $1,600 – $10,000 worth of materials. 

Based on the type of material, the cost will change. Usually, a wood foundation would present the cheapest material for foundation material.  

Plumbing Materials

Material costs are simpler to calculate. For plumbing, it gets easier. A typical home addition plumbing would require on average $2,500 worth of materials. This includes everything from the pipes to the fittings. 

You should not cheap out on plumbing material. Any sort of leak in the plumbing could end up damaging your home’s structural integrity. Both drywall and sheetrock are porous materials and absorb water quickly.

Over time, water-damaged walls can develop mold spores. This will even make living there a health risk. 

Electrical Materials

$2 – $7 per sq.ft. That is the cost of laying wires for the addition. For a 400 sq. ft. addition, it’d translate to roughly $1,200. On top of this upgrades to the service panel would require $1,780 on average. And each new switch and outlet would cost $125 on average.

Imagine you put a pair of lights, a fan and 3 outlets in the room. And don’t need to upgrade the service panel. You’d need to pay $1,950 for electrical materials. 

Whether or not you need to upgrade your service panel depends on a few factors. If there aren’t enough circuits on the panel for wiring your addition you must upgrade. Also, if you’re expecting to run heavy appliances in the new room, you should upgrade.

Walls and Floor Materials

You’ll need to pay $1 per sq. ft. of drywall. Insulation and paint would cost $2 – $6 per sq. ft. And flooring costs would range from $3 to $32 per sq. ft. depending on the material.

Adding all that up for a 400 sq. ft. addition means you’ll be paying $6,800 – $26,400. However, there’s one caveat here. If you’re purchasing paint you won’t be paying by the square footage. You’ll be paying by the gallon. 

One gallon of paint usually covers 400 sq. ft. That means you’d need about 3 gallons to paint the addition we’ve considered thus far. A gallon of paint costs $20 – $100. If you are having a tough time choosing a paint, buy one of these:

Product 1
Product 2

Adjusting for that the price range shifts to $4,460 – $19,500

Miscellaneous Costs

There are a few other costs you’ll need to consider.

Building Permit 

Before you can start building you will need to get approval for the project. A permit for a typical home addition project you’ll run you about $300


You’ll also need to pay for framing regardless of where you build. The average cost of framing an addition would be $800 minimum. The highest cost would be $12,000

For a 30 – 45 sq. ft. bump out, the framing cost would be $800. If you build a 400 sq. ft. on ICF blocks you’ll be paying $9,500

When framing by yourself you should look into concrete curing times. Whether the concrete is properly cured or not plays a big role in your addition’s stability.  

Summing Up the Cost For Adding a Room to a House

Let’s say you’re building a 400 sq. ft. addition. The addition is on the 1st floor. And, requires no plumbing. You’re also not expecting to go overboard. Instead, you’re expecting to pay for good enough materials.

For a project like that the price would be as follows. 

Hiring Help 

To keep the project simple you’ll have to get an architect. That would cost $5,200. There’ll be no complicated electrical work such as upgrading the service panel. Hence, you’ll only need to hire a general contractor. You’d pay $25,200 for that. 

You’ll also need to get a building permit. It’d cost $300. So in total, with the building permit, you’d pay $33,200

Preparing the Site

Since the addition is on the first floor you’ll need to extend the foundation. Assume you need to take down only one non-load-bearing wall. Therefore, you’ll need to pay $700 for the demolition. And excavate $2,300 worth of soil. 

The foundation installation will cost $6,000. And your site is ready. This means the total for site preparation is $9,000.

Getting the Materials 

Here’s the materials you’ll need for this project:

Material Cost
Foundation Material (Wood)$5,200
Electrical Materials $1,950
Drywalls, Insulation and Paint$4,980
Flooring (Wood) $9,200

Framing the House

At $12 per square foot framing the house would cost you $4,800

And with that your home addition is ready. The grand total sums up to $68,300.

Reducing the Cost For Adding a Room to a House

Taking all the assumptions we’ve made so far, you’ll likely pay $68,300. That is no small number. However, there are ways you can add more room without the huge cost. 


If all you need is some extra space in a room, you can do a bump-out. A bump-out is a basic extension of an existing room. 

These home additions do not require adding any foundation. The cost of a bump-out would be limited to the cost of drywall, flooring, and paint. And you’d need to factor in the labor and demolition costs.  

You can build a bump-out for as low as $5,000. And even the costliest bump-out would run you $30,000

Attic Rooms

You can convert your attic into a room. Based on the size of the attic you can expect to pay $8,000 – $30,000. For $30,000 you would be getting a fully finished room, with insulation and everything. 

For converting it into an additional bathroom you’d have to pay a bit more. Bathrooms need plumbing and as previously mentioned plumbing can get costly. However, it’d still be cheaper compared to adding a new bathroom on the first floor.

If you additionally have to change your roof. Then that too comes with the cost of replacing your roof.

Basement Room 

Basements are usually already structured well enough to be easily converted into a room. If you’re looking to build a bedroom, you’ll not need much work. The costs would be mostly in finishing the basement. 

If the basement is already finished it’ll cost even less. Just as it is for the attic conversion, converting it into a bathroom will cost more. On average a basement conversion would cost $12,000 – $30,000 depending on the size.

DIY-ing Certain Parts

Though doing the entire project by yourself isn’t something we’d advise, you can DIY certain parts. For example, you can paint the room yourself, or rent an excavator and prepare the site. Excavators can be rented for as low as $1,000 per week. 

You can also go for a premade plan. Instead of having an architect draw up a plan, you could buy a premade plan. These plans would cost less than hiring an architect and be very easily available. 

That covers everything about the cost of a home addition and ways of lowering it.

In case, if you were wondering about building a shed. The cost for a shed will be much lower than a room.


Question: How to remove trees from the construction site?

Answer: The best way is to hire an arborist. On average hiring, an arborist will cost $1,500 – $3,000. He’ll safely remove the trees on site. If there are any stumps left you can rent a power saw and grind the wood.

Question: How much will it cost to extend existing systems?

Answer: Extending existing systems isn’t very costly. For example, moving a septic tank would cost $2,000 – $3,000. Moving an electrical panel would cost anywhere between $800 – $1,200. Extending gas and electric lines would cost $15 – $27 per foot

Question: Does every room need a separate circuit?

Answer: No. Not every room needs a separate dedicated circuit. However, let’s say you’re going to use the room for running heavy equipment. In that case, you’ll need a dedicated circuit. Besides, it’s a good practice to put every room on a separate circuit. That’ll prevent overloads and reduce the chances of accidents. 


How much does it cost to add a room to a house? The basic answer is there’s no straight answer. You’ll have to consider the size and location of the build. The materials used will also affect the cost.

Hope we’ve answered your question and helped you calculate your own price.

Good luck!