How Much Does a Sunroom Addition Cost in Ontario, Canada?

How much does a Sunroom Cost?

Curious about the cost of a new sunroom addition? Sunrooms are a wonderful way to expand your living space, bring in more natural light, and enhance your lifestyle! 

If you’re considering building a sunroom or home addition in Southwestern Ontario and wondering the costs, we’re here to help! The price of a sunroom in Ontario can vary widely depending on factors such as size, materials, design, and whether it’s a seasonal (three-season) or year-round (four-season) structure.

Each sunroom is custom-designed to fit your home, lifestyle, and site conditions. In 2025, the average cost of a Four Seasons Sunroom ranged from $85,000 + tax to $95,000 + tax. Later in this article, we break down the factors that influence pricing to help you understand your investment.

Where to Start?

Building a Four Seasons Sunroom or home addition is an exciting way to expand your living space and bring more natural light into your home.

Most homeowners start their research online to get a sense of pricing, styles, and inspiration. While this can be helpful, it often leads to confusion—especially when it comes to understanding true sunroom costs.

Many online results can be misleading. For example, low-cost sunroom kits advertised between $2,000 and $20,000 are often sold by overseas, online-only retailers. These products typically use low-quality, non-insulated materials and are not designed to handle Canadian climates or snow loads.

You may also come across websites, platforms, or influencers offering home improvement advice or contractor connections. These sources often display pricing in USD instead of CAD and may not reflect accurate or realistic costs for Canadian homeowners.

In many cases, this information is created by individuals with limited experience in sunroom construction and lacks the detail needed to make informed decisions.

With over 30 years of experience designing and installing sunrooms and home additions across Southwestern Ontario, we’re here to help.

In this guide, we’ll walk you through the key factors that influence the cost of adding a sunroom to your home. Understanding these elements will help you estimate your project more accurately and make informed decisions with confidence.

If you’re already familiar with the costs and ready to take the next step, you can book a design consultation with our expert designer to receive a detailed sunroom design and personalized quote.

7 Key Factors That Affect Sunroom Costs

1. What’s Already in Place?

If your deck has an existing roof, such as a covered porch, we can often enclose this space with sunroom walls without major structural modifications. It’s important to keep in mind:

• • Decks are generally not designed to support a structure on top.
  • Floor joist size matters. Anything smaller than 2×8 joists is usually unsuitable.
  • Foundation beneath the deck is crucial. In Ontario, Canada, building codes require footings to be at least four feet deep to prevent shifting during freeze-thaw cycles.

A proper assessment is always recommended to ensure the structure is safe and up to code. If you’re unsure whether your deck was built with a permit, your municipality may have records of its foundation and construction, which can help determine whether it’s suitable to build upon.

2. Four Season Sunrooms Materials & Insulation

Consider how you plan to use your sunroom, while keeping in mind the more insulation and energy efficiency, the higher the cost of your sunroom.

• •      Screen Rooms – The most affordable option, offering protection from bugs and some weather elements.
  •     Three-Season Sunrooms – Built with single-pane glazing, providing shelter from wind, rain, and insects.
  •     All-Season (Four-Season) Sunrooms – Constructed with insulated aluminum structure and Insulated Glass to withstand year-round Canadian weather.
  •     Fully Integrated Home Additions – Featuring vinyl windows and doors, meeting building code requirements to open an addition up  to your home (e.g., knocking down a wall in the house to have a sunroom open concept).

At Four Seasons Sunrooms & Additions, we provide a variety of solutions, from screen rooms, sunrooms and year-round home additions. 

3. Four Season Sunrooms Sizes

It’s important to think about the size of the space you want. To get a clearer idea, try measuring an existing room in your home. Remember, the larger the sunroom, the higher the overall cost will be.

• •     Measure the size of the space you want.
  •     Consider what furniture you plan to use.
  •     The larger the sunroom, the higher the cost.

4. Roof Integration with Your Home

Each sunroom we design is attached differently, depending on your home’s structure.

For example, in multi-storey homes, the sunroom roof can often be connected directly to an existing wall for a clean, seamless transition. In bungalows, however, modifications to the existing roofline are often required to ensure proper drainage and integration.

These adjustments are important to maintain structural integrity and prevent issues over time.

• •     Multi-Story: attaches seamlessly to an existing wall.
  •     Bungalow: modifications to the house roof may need to be completed to ensure proper water drainage and integration.

5. Roof Type for Your Four Season Sunroom

At Four Seasons Sunrooms & Additions, we provide a variety of roof options to suit your specific needs and preferences. Here’s a quick look at what we offer:

• •     Prefabricated Solid Roofs – Low maintenance, ideal for low-pitch roofs.
  •     Conventional Roofs – Designed to blend seamlessly with your home’s aesthetic.
  •     Glass Roofs – The most premium option, allowing maximum natural light into your sunroom offering a WOW factor.

6. Heating & Cooling Options

When planning how to heat and cool your sunroom, it’s important to consider the local climate, the size of the room, and how you plan to use the space. These factors can also influence the overall cost of your project. Here are some common options for heating and cooling a sunroom:

• •   Electric heating & cooling units
  •   Fireplaces
  •   In-Floor Heat

7. Additional Work & Customization

When designing your new sunroom addition, it’s important to be aware of potential additional costs that may arise. While these aren’t always required, knowing about them in advance can help you manage your budget effectively. Some common examples include:

• •   Electrical requirements
  •   Exterior decks or patios
  •   Finished Flooring materials
  •   Interior finishes

So, What Does a Four Season Sunroom Really Cost?

In 2025, the average cost for one of our sunrooms ranged between $85,000 + tax and $90,000 + tax. However, since each sunroom is custom-designed and built to meet your needs and the specifics of your site, there isn’t a standard price per square foot. While the information in this article is important to recognize and consider, we’ve outlined some starting costs for our most popular sunroom models below:

Sunrooms

• • Three-Season Sunroom (12’x12’ – Solid Roof): Starting at $60,000 + HST 
  • Four-Season Sunroom (12’x12’ – Solid Roof): Starting at $71,000 + HST
  • Four-Season Sunroom (12’x12’ – Glass Roof): Starting at $83,000 + HST
  • Conservatory (12’6” x 12’6”): Starting at $114,000 + HST

Patio Covers

• • Patio Covers  (Glass Roof) (12×12): Starting at $40,000+HST  
  • Patio Covers  (Solid Roof) (12’x12’): Starting at $23,000+HST 
  • Louvered Roof Pergola (12’x13’): Starting at$35,000+HST 

What Now?

Book Your Design Consultation!

While there’s no one-size-fits-all price for a sunroom addition, understanding the factors that influence cost can help you plan your project with confidence.

At Four Seasons Sunrooms & Additions, our sunrooms are built to last, enhancing your comfort, lifestyle, and the value of your home. We look forward to earning your trust and delivering the highest quality, so you can enjoy your sunroom for many years to come.

For exact pricing and a personalized consultation, contact us today!

Phone: 1-888-786-7666 (1-888-SUNROOM)
Email: info@sunroomdesign.com