Do Sunroom Additions Need Foundations? What You Need To Know

A common question about sunroom additions is whether or not they need a foundation. In this blog post, we’ll explain how to know if your sunroom needs a foundation.
A sunroom with couches and a rug in it.

Adding a sunroom to your home is a great way to add value, extra living space, and natural light. But one of the biggest questions prospective sunroom owners have is whether or not they need a foundation for their sunroom additions. The answer, like with most things in life, is it depends. Several factors need to be considered before a decision can be made. 

In this blog post, we’ll break down what factors influence whether or not your sunroom needs a foundation and what you need to consider before installing a sunroom. 

What Factors Influence If A Sunroom Needs A Foundation?

Construction workers in the process of forming a concrete slab for a sunroom addition.

Among sunroom additions, those set on a foundation are the most sturdy and permanent. But not every sunroom needs or benefits from being built on a foundation; in some cases, it may not be possible or advisable to do so. So what factors influence whether or not your sunroom will need a foundation?

Let’s look at what factors go into this decision and how you can determine if your sunroom needs one.


Consider the climate where you live. If you live in an area with severe weather conditions—high winds, heavy rains, deep freezes—it’s likely that your sunroom will need to be built on a foundation to withstand the elements.

For example, if you live in an area with harsh winters, you’ll likely need a foundation for your sunroom. This is because the added weight of the sunroom can cause the ground to shift and settle, leading to cracks in the structure. 

On the other hand, if you live in a more temperate climate, your traditional sunroom may get by without a foundation.

Size And Weight

Think about the size and weight of your sunroom. Is it a heavy custom-built four-season room? Heavier sunrooms will need a more robust support system, which a foundation can provide. Larger sunrooms may also need a foundation to meet local building codes.

Similarly, the taller the room, the more likely you’ll need a foundation. That’s because more elevated structures are more susceptible to wind damage. Foundationless sunrooms are only typically seen on single-story homes. 


Consider the design of your new room. If you’re planning a simple structure made of lightweight materials, it’s unlikely that you’ll need a foundation.

However, suppose you’re planning a more elaborate sunroom with brick walls and a glass roof. In that case, a foundation will be necessary to support the weight of the materials. Need some inspiration for your sunroom design? Check out our guide on how to design a sunroom.

Type Of Sunroom

Another factor to consider is the type of sunroom you plan to install. If you’re planning on adding a conservatory-style sunroom, then it’s likely that you’ll need a foundation. These sunrooms are typically tall and made with glass, making them susceptible to wind damage. 

On the other hand, prefabricated sunroom kits with steel, aluminum, or fiberglass frameworks may be light and sturdy enough to not require a foundation. They’re often designed to be installed on existing structures like patios or decks. 

If you are assembling a prefab sunroom yourself, follow the manufacturer’s instructions, or hire a qualified technician to put it together for you.

Local Building Codes

Before you start planning your sunroom addition, it’s essential to understand the building code requirements for such a project. In many cases, sunrooms need a foundation just like any other room in the house.

The exception is if the sunroom is built on an existing covered space, such as a porch or deck already adequately supported. So before you begin construction, check with your local building department to ensure that you’re following all the necessary code requirements.

Sunrooms may require a foundation in other jurisdictions due to local weather or geologic phenomena. For example, sunrooms located in earthquake-prone areas must be built on a concrete slab foundation. Similarly, sunrooms in hurricane-prone areas must be made on post and pier foundations. 

As you can see, there are several factors to consider when deciding whether or not your sunroom needs a foundation. But careful planning and consideration can determine what’s best for your home.

How Is A Sunroom’s Foundation Installed?

Sunroom with wide open sliding doors with wooden and wicker furniture inside and a stone tile walkway and grass.

Sunrooms are a great way to add extra living space to your home. But before you can enjoy your new sunroom, you must ensure it is properly installed.

Foundation Installation

The foundation of your sunroom is one of the most critical elements, and it needs to be installed correctly to ensure the stability of your sunroom.

The most crucial step in installing a sunroom foundation is to level the ground. This can be done by excavating areas too high and filling in low spots. Once the ground is level, you can begin laying the foundation.

Although you can save money by laying your foundation, we recommend using a professional contractor to ensure it is correctly installed and meets local building codes.

Keep reading to learn how each type of foundation is installed.

Types Of Foundations

There are two main types of sunroom foundations: post and pier and concrete slab. Let’s take a closer look at the differences between these foundation types and how they are installed.

Post And Pier

Post and pier sunroom foundations consist of concrete piers that support the weight of the sunroom. This foundation is commonly used for sunroom additions and other similar structures.

The foundation consists of a network of posts and piers supporting the sunroom’s weight. The posts are driven into the ground, and the piers are installed on top of the posts.

The sunroom is then attached to the piers.

Post and pier foundations are generally less expensive than other types of foundations and can be installed relatively quickly. However, they are not as sturdy as other types of foundations and may not be suitable for all types of sunrooms.

If you’re considering adding a sunroom to your home, talk to your contractor about whether a post and pier foundation would be suitable for your project.

Concrete Slab

Most sunroom additions are built on a concrete slab foundation. Concrete slab sunroom foundations are made of poured concrete extending around the sunroom’s perimeter.

The process of installing a concrete slab foundation is relatively straightforward. First, the area where the sunroom will be located is excavated to a depth of several inches.

Next, a layer of gravel is spread over the excavation site to help drainage. Forms are placed around the perimeter of the excavation site, and steel reinforcement rods are placed within the forms. Forms are usually created using 2×4 or 2×6 boards.

After that, concrete is poured into the forms and allowed to cure. Once the concrete has cured, the forms are removed and the sunroom addition can be built on top of the slab foundation.

What Do I Need To Consider Before Having A Sunroom Installed?

Sunroom addition with wicker furniture.

Adding a sunroom to your home can be a great way to add extra living space and enjoy the outdoors without having to deal with extreme weather conditions. However, there are a few things you need to consider before having a sunroom installed.

Type Of Sunroom

You need to decide what type of sunroom you want. There are three main types of sunrooms: conservatory sunrooms, solarium sunrooms, and screened-in sunrooms.

Conservatory Sunrooms

Conservatory sunrooms are typically made with all glass walls and ceilings and can get very hot in the summer. Conservatory sunrooms often incorporate double-glazed windows and insulation features, making them even more efficient. 

Solarium Sunrooms

Solarium sunrooms have more ventilation and are better for homes in cooler climates. They typically have large windows that extend from the floor to the ceiling and may even have skylights. As a result, solarium sunrooms can get quite warm, making them ideal for sunbathing or growing plants that need lots of light. 

Screened-In Sunrooms

Screened-in sunrooms provide protection from insects and other pests. As a result, screened-in sunrooms are a great way to enjoy the outdoors without worrying about the elements. Screen rooms can also help keep your home cool in the summer months by blocking direct sunlight. 

Right Location

Once you’ve decided on the type of sunroom you want, you must choose the right location. Sunrooms should be built on a level part of your home with good exposure to sunlight.

The best place to orient a sunroom is usually south or east-facing. You also want to make sure that the sunroom will be comfortable in the climate you live in.


Finally, you need to know the potential cost of adding a sunroom. Sunrooms can be very expensive, so get a few estimates before making a final decision. You may also want to include the cost of sunroom furniture in your budget.

Considering these factors, you can be sure that your new sunroom will be a beautiful and functional addition to your home.

Let Classic Home Concepts Help Bring Your Sunroom Addition To Life

As you can see, many factors go into deciding whether or not your sunroom addition needs its own foundation. If you’re unsure whether or not your planned sunroom will require a foundation, fill out our contact form today.

Our team of experts will walk you through the process and answer any questions about sunroom additions, foundations, and more. We look forward to helping you create the perfect space to enjoy the beautiful Missouri weather all year!