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The average costs to build a home addition

The average costs to build a home addition

Exterior renovationsThe average costs to build a home addition

When you first move into your home, it could be the ideal size and shape for the number of people as well as everything you own. Of course, as time goes by, you may accumulate more and more stuff and your family may grow in numbers. This could give the impression that your home is getting smaller and smaller and thus, the need, or simply the desire, to expand. Of course, a house extension or addition is generally possible, but what are the costs involved in such a large-scale project?

If your home no longer meets your needs space-wise, it's time to think about how you can take on a house extension project, as well as the related costs involved. Luckily, we’re here to lay down the average costs and important information on the subject! We'll delve into planning, designing, and a few other things. 

The Average Cost of a Home Extension

home extension

Source: Canva

How to Plan a Home Extension Project

Naturally, before you grab a hammer and welcome your builder buddies over, there are a few steps you’ll need to consider, and rightfully so. First, have you considered hiring homebuilders and an architect? It may be an important step to ensure that the room or space you’re planning on adding matches the rest of your home, even if it's a rear extension. Another consideration is hiring a structural engineer so that the extension design will get built without compromising the structural form of your house. If you don’t already know about load-bearing walls, well now might be a good idea to get your research on! Hiring an architect, contractor, or structural engineer is crucial to making sure any home extension project happens in the safest manner possible.

Then, you'll have to consider your options! Do you want a kitchen extension, new spaces altogether, garage conversion, or a simple single-storey extension? The possibilities are quite endless, and there's truly something suited for all families and households. It very much depends on the location of the original house and making the right decisions along the way. 

Extended Home: Adding a Room

One of the most common types of home extension is building an extra room. As above-mentioned, large, open kitchens are on trend right now, and might be a great home extension project. This could also mean an extra bedroom on an additional floor, living or dining room extended out of the side of your house. With an extra room addition, it is only possible to build upward or outward. Building out will involve adding a room on the ground floor, and this is generally the preferred method of construction for smaller or older homes, which may not be able to take the structural weight of a second-storey addition. As it may be obvious, building out will increase your home's footprint.

You may not have the ground support or foundation to take on this job, and thus it could be quite expensive to build a new foundation as well as obtain the licences required to expand. On the other hand, building up does not involve increasing the footprint of the home. However, this project may require a professional hand as there could be a necessity to strengthen the foundation to support the additional weight. Adding an extra room to your home can average anywhere between $95-$360 per square foot.

Conservatory or Glass Extensions

Sunrooms and conservatories are another common house extension, often built out and added to the side of a home. Again, the cost of a sunroom will vary depending on the amount of space you intend on covering and if you’ll be including electricity and heating in the room. Make sure to get multiple estimates for this project and look for the best prices possible, especially because of the materials involved when building this type of addition. A sunroom will average between $18,000 and $95,000, including the costs of hiring an electrician.

Backyard Detached Extension

This is an option for homeowners who don’t have the structural integrity or space directly beside their home for the aforementioned extensions. This will be a shed-like structure or something similar. Rooting heating and electricity may be tricky depending on your property, so do take these costs into consideration. Your detached extension can cost between $19,000 and $30,000.

How much does it cost to build a home addition/extension in Canada?

home extension

Source: Canva

When it comes to building up, meaning adding another storey, home addition costs may range between $180-$300 per square foot. When it comes to work done on one floor only, or an unfinished basement that's to be only widened, costs will be roughly between $360-$480 a square foot. If you're working on a basement, finishing details will add costs of about $90 per square foot. Something to bear in mind is that the greater the size of the work, the lower the price per square foot will be!

For an extension spanning two floors, the first floor will cost between $360 and $480 per square foot but the second floor will cost between $210 and $240 per square foot. Regardless of the size of the work area, it is important to have a minimum budget of roughly $72,000 for a proper extension on your home (most likely between $120,000 and $240,000). Note that these are ballpark costs and do not take into account the particular characteristics of each room (plumbing, heating, windows, etc.).

We have formulated a small price guide that, depending on the nature of the work, could give you the cost of a home extension by the square foot.

How Best to Calculate the Cost of a Home Extension Project

For the majority of the work, the best method consists of a simple calculation: the cost of materials added to labour costs based on the number of hours it will take to complete the work. As we mentioned earlier, in the case of a house extension, the cost is difficult to estimate because of the intricacy of the work. As a result, it’s best to ask for a quote from a certified contractor.

Professionals are well-suited and sufficiently skilled to give you a fixed price without risking leaving out aspects that will increase the cost. Of course, after receiving a quote, do make sure to leave enough wiggle room in your budget for any unpredictable issues or problems, which can be a common occurrence with large renovation projects, like adding a new space onto your home.

What's the cheapest way to extend a house?

It’s difficult to pin down the specific costs when it comes to a home extension project, and that’s because many factors will influence the costs of such a project. It’s important to take into account that each quote received from contractors, builders, or architects could greatly vary in terms of cost and timeframe and note that several factors can influence the overall price tag. However, it's still a great way for you and your family to grow with your home. 

First off, the level of complexity of the work will majorly influence the price at the end of the road, and can ultimately increase or lower costs, just like the extension style will too. The number of scaffolds, proximity to busy streets, and commercial districts are other examples of factors that will likely influence the costs of construction. The types of materials you’ll be using as well as the type of materials already in place will also contribute to increased costs.

Cost Overview of a Home Extension Project

Type of project or material
Average price

Installing a new floor on a house

approx. $180 to $300 per square foot

Transforming a floor

approx. $360 to $480 per square foot

2 floor home addition (1st floor)


approx. $360 to $480 per square foot

2 floor home addition (2nd floor)

approx. $210 to $240 per square foot

Minimum budget for a home extension project

$72 000 (in general, $120 000 to $240 000)

For more information about home extensions, check out "The cost of a home addition project"

To learn more about the average prices of home renovation projects, consult our "Home renovation price guide". 

Get 3 renovation quotes for your home addition project can help you get quotes for your home extension project. If you submit your project to us, we’ll put you in contact with top-rated contractors. Fill in the form on the homepage (it only takes a few minutes), and you will get estimates from trusted professionals. 

Dial 1-844 828-1588 to speak with one of our customer service representatives.

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Last modified 2023-11-07

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