According to the Canadian Government, vegetable greenhouses are the largest and fastest-growing sector of Canadian horticulture (as of 2016).
From vegetables to landscaping plants, Canada has a vibrant greenhouse industry. But, if you’re considering building a greenhouse, there’s something important you need to know…
Choosing the right foundation for a greenhouse is critical.
Because besides a healthy greenhouse industry, there’s something else Canada has in abundance (especially in Manitoba): Tough weather, and tough soil.
Those factors can make finding the right greenhouse foundation trickier than it would seem at first glance.
Today, we’re going to show you why the most common foundation for greenhouses could pose a big problem (and how you can avoid it).
What Makes a Greenhouse Tricky to Support?
If you’re like most people, you probably don’t spend too much time thinking about the foundation of a building.
Don’t worry, that’s not a bad thing. In fact, if a foundation is doing its job than you should never have to think about it.
If you’re interested in building a greenhouse, then you really do need to think about the foundation.
Traditionally, the most popular foundation for a greenhouse has been poured concrete piles. This type of foundation consists of digging a hole, installing a special tube form, setting rebar, pouring concrete, and waiting for it to set.
Here’s the thing about concrete piles and greenhouses…
Compared to other structures of the same size, greenhouses are relatively light. This presents a problem for concrete piles.
See, concrete piles do work well under heavy, well-heated structures like large family homes. That’s because concrete piles need a good amount of weight pressing down on them, to make sure the forces of frost can’t heave them out of the ground.
Frost is one of the most powerful forces in nature, and it can literally move buildings. When moisture in the ground freezes, it causes expansion. Manitoba has soil that’s highly prone to expansion, so the frost-induced expansion places an incredible amount of force on a foundation.
If a concrete foundation doesn’t have enough weight on it, then frost will cause the foundation to heave. Over time, this will cause damage to the greenhouse and can even lead to foundation failure.
There’s another consideration to make when thinking about concrete piles under a greenhouse.
A greenhouse is humid. That’s not very surprising, considering the point of a greenhouse is to offer a warm and humid environment. Unfortunately for concrete piles, that humidity is a problem.
Concrete is porous, meaning it has nooks and crannies that moisture can seep into. As moisture seeps into these piles during winter, it quickly freezes in the concrete. This expands the concrete, causing cracks and degradation in the pile. Over time, this can even lead to a total loss of structural integrity in the foundationw.
So, we’ve established that concrete is likely not the best foundation for a greenhouse. What’s a better choice for a greenhouse foundation?
Screw Piles: An Ideal Greenhouse Foundation
Screw piles are an excellent alternative to traditional concrete piled foundations for greenhouses.
Instead of relying on excavated holes and poured concrete, screw piles take an entirely different approach to foundations.
Built from galvanized steel, a screw pile is essentially a large screw. It turns into the ground with the power of hydraulics and provides exceptional support in even the poorest soil conditions.
The differences comes from the helical blade, towards the bottom of the screw pile. This helical blade creates a strong anchor point that is highly resistant to frost heave. Because the shaft of the screw pile is relatively narrow in comparison to the helical blade, the screw pile can better defend against ground movement.
A screw pile doesn’t require heavy weight to keep it from heaving. In fact, a helical screw pile can sit in the ground with no weight on it at all and still it won’t heave. This makes screw piles an ideal foundation for greenhouses.
Offering peak performance under light structures isn’t the only thing to think about when comparing screw piles to concrete. Resistance to moisture is another area which screw piles excel.
At Postech, we only carry hot-dip galvanized screw piles manufactured from Canadian cold-rolled steel. Our screw piles are so resistant to rust and corrosion, they have an average life of over 200 years in the ground.
If you recall from earlier, concrete piles are porous. This can lead to moisture working into the pile and freezing in winter. Not a good situation for the concrete.
Screw piles, especially galvanized piles, don’t have this problem. They will happily perform in humid environments without any issues. Because moisture can’t infiltrate the screw pile, it can’t cause any damage.
And, those aren’t the only benefits to screw piles! Here’s some more pluses to using screw piles under a greenhouse:
- They install faster than concrete
- They’re less mess than concrete, because you don’t need to excavate holes for the piles
- The equipment used to install screw piles is compact and unobtrusive – no cement trucks running around your site
- They’re environmentally-friendly, and can even be removed from the ground and reused if you ever need to move the greenhouse
- In many cases, they can end up being more affordable than a comparable concrete piled foundation
What’s the Final Word on Greenhouse Foundations?
We’ve said time and time again on this blog, there’s no “one foundation” that works in every situation. And, any company who tells you they have the “perfect foundation” is lying.
That said, a screw pile foundation can be a great choice for greenhouses. Their resistance to frost heave, durability in damp conditions, and ease of install make screw piles a logical solution for most greenhouse installations.
If you’re curious about screw pile foundations for greenhouses, click here to get in touch with us! Our friendly foundation experts are happy to give you a free foundation consult, and let you know if screw piles are the right fit for your greenhouse.