Installing a three- or four-season solarium: mistakes to avoid

Want to make summer last a wee bit longer and enjoy the sun even on cooler days? The ideal solution is to add a solarium to your residence. Besides making the most of the sun, this type of extension offers many other advantages: it increases your home’s resale value, and offers passive solar gain, additional living and storage space, etc.

But, if you think that simply adding this structure onto an existing balcony is enough to enjoy the sun’s rays, you’re mistaken. Installing a 3- or 4-season solarium should not be taken lightly! Several factors must be considered to ensure solidity and durability.

So, to help you avoid any disastrous mistakes, we have come up with a list of the most common solarium installation blunders. We will attempt to shed some light on them for you:

Choosing the wrong type of solarium

There are two types of solariums available on the market: the 3-season solarium, not usable in the winter, and the 4-season, comfortable year-round. The key difference, besides the price? Heating! The 4-season solarium can be heated, but not the 3-season.

Here are some other differences:

3-season solarium

Less expensive than its 4-season counterpart, the 3-season solarium can be enjoyed in the spring, summer and fall. A lighter structure, it requires much less work to install. A structurally sound balcony or a terrace is usually enough to support this type of solarium.

Single pane (but tempered glass) windows are enough to maintain it at a comfortable temperature.

4-season solarium

A 4-season solarium allows you to enjoy the sun’s rays year-round, even in the depths of winter. It is more expensive than the 3-season solarium because of its composition and energy consumption.

The 4-season solarium’s aluminum structure must have a thermal barrier and double or triple paned glass. To avoid condensation and drafts, the temperature must be constantly controlled through effective ventilation, insulation and heating.

Heating your 3-season solarium to use it all year

If you think you can save money by heating your 3-season solarium, think again! This is actually inadvisable as it causes undue condensation.

Opting for lesser quality foundations

To ensure that your solarium remains firmly in place for years to come, you must choose solid foundations that are not affected by ground movements due to the frost and thaw. If not, your structure will shift and sink over the years.

Therefore, Pro Post Foundations’ screw piles, anchored into the ground below the frost line thanks to a helix plate at the bottom of the shaft, represent the best option as they will always remain stable. And, they can be used in any type of soil, whether dense or aqueous.

To support a heavy, 4-season solarium, the number, dimension and placement of the screw piles will be determined by our expert installers or our in-house engineers.

When it come to installing screw piles, the machinery and work required are substantially less than a traditional concrete foundation. In fact, as opposed to the large machinery that is essential when pouring a concrete foundation, our mini Kubota tractor, with its turf tires, will not damage your lawn.

If you do choose a concrete foundation, because of the empty space below the structure, we highly recommend that you install heated flooring, unless you use choice insulation.

Building your solarium on a rickety balcony or terrace

Installing your 3- or 4-season solarium on an existing balcony or terrace is conceivable, but you must be sure that the structure is perfect. It must not be affected by ground movements due to the frost and thaw; if the supporting structure shifts, water will infiltrate your solarium.

If you want to reinforce the foundation of an existing balcony or terrace prior to installing your solarium, you will be happy to know that screw piles can be installed under the current structure. In fact, our versatile equipment even enables us to install in constricted areas.

Choosing low-quality glass

Particularly if you are opting for a 4-season solarium, you must select high-energy efficiency glass that will keep you comfortable all year, even in winter. How do you evaluate glass quality? By using its isolation factor. A product’s thermal resistance is expressed by its R-factor: the higher the R-factor, the better it insulates.

For a solarium, the minimum required R-factor is R-4. With tinted windows, blinds in the summer and radiant floors in the winter, you will be very comfortable in your solarium. Understand that the R-factor can go to 13, and as of R-7 the cost increases exponentially!

Omitting to install a hermetic door between your 3-season solarium and your house

A three-season solarium can be enjoyed even when the temperature outside drops below zero. Believe it or not, when it is -5 °C, even -10 °C, outside, you will still be comfortable because the solarium’s windows capture the sun’s rays, thus rising the temperature!

But, at night, without the sunlight, the freezing point can easily be reached! Therefore, to avoid temperature variations in your home, it is highly recommended that you install a well-insulated hermetic door between your main residence and your solarium.

Sealing inadequately between the house and the structure

One of the most frequent issues with solariums is water infiltration; the main reason for this is a poor seal between the house and the addition. When the solarium leans against a brick wall or it must be attached to the fascia (the extremity of the outer wall), the risks are tenfold.

Calling on an entrepreneur who specializes in solarium installations will ensure your peace of mind.

Not having a professional install your solarium

It is possible to install your own solarium, but doing it successfully requires extensive knowledge; all the necessary information cannot be found in an instruction manual. So, if you do not call upon an expert, chances are that you will have water infiltrations… a lake in the summer and a skating rink in the winter! To ensure durability, we recommend that you budget for a professional installation.

Not validating with your municipality beforehand

Whether heated or not, a solarium is considered an annex or an addition, and it must conform to your municipality’s regulations relating to materials, fire codes, distance from neighbours, and the type of foundations allowed.
Before jumping into this project, why not find out what is and is not permissible, and obtain a building permit from your municipality, if necessary; this way, you will avoid any unpleasant surprises!


So, there many things to consider, before you build or install your solarium. The type of solarium, the building materials, the contractor, the municipal regulations and your foundation; it is key to be well-informed and give yourself enough time prior to jumping into such a project.

Now that you have thought about everything, why not call on the professionals at Pro Post Foundations to install your future solarium?

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