Do Greenhouses Need a Base?

Buying a new greenhouse can be an expensive exercise, so it’s natural to try and economize where possible. One common consideration is whether greenhouses need a base, as these can significantly add to the cost of getting into greenhouse gardening. 

The reality is that a greenhouse base should be considered an essential purchase when buying or upgrading your greenhouse. 

In this article we’ll discuss why that is, we’ll look at some common examples of greenhouse bases and I’ll provide some useful hints and tips from my own experiences of greenhouse ownership. 

Why Do Greenhouses Need a Base?

Greenhouse bases serve a number of important features:

Structural Rigidity

Whether you choose a plastic or aluminium framed greenhouse, there will be limits on what it can withstand. Strong winds, for example, can cause issues with some greenhouse frames. In these situations the glazing can work loose or can crack under the additional pressure. Anything we can do to prevent this can save a lot of money and effort in the long run.

This is exactly what greenhouse bases do. They provide additional structure to the bottom of your greenhouse, helping to strengthen it against storms and other physical pressures. In doing so you’ll greatly extend the lifespan of your greenhouse whilst simultaneously keeping it in the best condition possible.   

Evened Load

For the longest life possible the weight of your greenhouse should be evenly distributed on a level bottom. 

If a greenhouse is laid on uneven ground these differing pressures from the ground can result in some panels loosening or distorting over time. This can make your greenhouse less effective as gaps can appear that allow cold draughts or rodents in. It can also lead to expensive repairs.

A good-quality greenhouse base, in contrast, helps to spread the weight of your greenhouse evenly, keeping it in tip-top condition for longer. 

Firmer Anchoring to the Ground

In some situations the wrong gust of wind may be at risk of raising your greenhouse off the ground. This is obviously a very bad thing. While it can apply to greenhouses of any material, plastic greenhouses are normally lighter so can be at particular risk of movement in windy weather. 

Most greenhouse bases help to reduce the chances of this happening to allowing you to firmly anchor your greenhouse to the ground. 

There are a number of ways this can occur depending on the materials you use for your base but can include long spikes which are pushed deep into the ground or anchor points that are attached to heavy objects such as paving slabs or concrete.

Additional Height

Lastly, while this is probably the least impressive benefit of greenhouse bases, some models will raise your greenhouse up by a few inches. This in turn can provide more headroom for both you and your plants. This is especially valuable for tall gardeners or those of us planning to grow tall or climbing plants.

What Types of Greenhouse Base Exist?

Broadly speaking when we talk about “greenhouse bases” this can mean one of two things:

Metal Base Frame

Metal frames can work well as greenhouse bases, ensuring structural rigidity while at the same time increasing vertical space in your greenhouse. They often come with fixtures to help secure your greenhouse to the ground. The most common greenhouse base frames are made from sturdy material such as steel, which can also help to weigh down your greenhouse in high winds. 

These frames come in a wide variety of sizes, and are often purchased as a kit. Construction at home is simplicity itself with the use of some basic hand tools. Some greenhouse retailers will even include an appropriately-sized base frame at a discount when it is bought with the greenhouse. 

Once constructed you can then place it into position, put the constructed greenhouse on top and fix the two together so they appear as one solid unit. 

Groundworks

An alternative use of the phrase “greenhouse base” refers to basic groundworks placed under the sides of your greenhouse. Common examples can include concrete laid specially for the purpose, standard garden paving slabs or plastic “eco tiles” which slot together. Either way these elements are usually sunk to roughly ground level, with great care being paid to ensuring a perfectly level surface. 

These groundworks can serve a number of benefits. Firstly, of course, they ensure your greenhouse is level and that the weight is distributed evenly. In this way your greenhouse won’t be placed under any unnecessary stresses, which should extend it’s life considerably.

However while this is the most important reason, this is far from the only reason to consider such a base. A well-laid base can also prevent your greenhouse from sinking over time, as can happen in cases of heavy extended rainfall, such as during the winter. 

Here the earth can become sodden with water, and heavy objects like greenhouses can be at risk of moving. While the movement might be almost imperceptible to the human eye at first, over time this can cause damage to greenhouse frames.

A solid base like this gives you an additional option for securing your greenhouse. For example, paving slabs can be drilled, and fixtures can be used to firmly and permanently attach your greenhouse to these slabs. This further keeps your greenhouse properly-grounded in bad weather.

These solid footings can be useful for protecting your greenhouse from unwanted vermin as they make it difficult to burrow underneath. Any mouse or rat that tries it will have to burrow some considerable distance to get in, thanks to the paving slabs on which your greenhouse now rests.

Lastly, consider that the use of concrete or slabs can help retain the sun’s warmth after a sunny day. They will then gently release this heat back into your greenhouse at night, acting like a storage heater, and so keeping the interior temperature more pleasant.

What is the Best Greenhouse Base?

As we’ve seen, while the phrase “greenhouse base” can actually be applied to two different elements of your greenhouse, both can serve important benefits. But which is really “best” if you’re on a budget? 

Broadly speaking these two forms of greenhouse base should not be considered an “either, or” situation. Instead, they work best when combined – a metal base frame that is then subsequently placed onto firm footings. This arrangement will allow you to keep your greenhouse in perfect condition for years to come, so should be considered a worthy yet necessary investment. 

When selecting a greenhouse base here are some things to consider:

Metal Greenhouse Base Frames

Strength – The stronger your base frame the better. This generally means opting for a heavy-duty option if one exists. 

Aluminium may be lighter and cheaper in some cases but it is also quite a pliable metal and may struggle to take the weight of a larger greenhouse. 

Steel frames can be heavier and more expensive but are generally sturdier and will cope with heavy greenhouses much better.  

Waterproofing – Your greenhouse base is going to be exposed to lots of water, not just when you’re tending to your plants but also from rain in winter. Remember that your base will be close to – if not in contact with – the ground. 

Anything that rusts or rots too quickly when damp is therefore unsuitable. Don’t consider a wooden frame, for example, no matter how attractive they may be. 

Instead look for galvanised or painted metal. Painted bases can look more attractive, but you’ll need to keep an eye on the paintwork in the coming years and fix any chips that develop.

Appearance – Your greenhouse shouldn’t just be a practical place to grow plants – it should be an attractive feature of your garden in it’s own right. As metal greenhouse bases come in a range of different colors and finishes consider which will look best with your intended greenhouse. A nice black-framed greenhouse, for example, could look quite odd if placed on a silvery galvanised base. 

Weight – Steel greenhouse base frames tend to be heavier than their aluminium cousins. The weight still isn’t excessive in any way, but if you are older or have a physical disability then the weight of the frame may be a consideration. Most good retailers will provide the package weight so you can assess whether you’ll be able to construct the frame with ease.

Getting it Home – A metal greenhouse base frame needs to get to your house somehow. Whilst they are generally sold in kit form, it still means that the box is going to be roughly the same length as your greenhouse. 

Even a small greenhouse base can therefore take up quite a bit of space in your car if buying from a garden center. My greenhouse is 12 feet long, so picking it up myself just wasn’t an option. 

Buying a greenhouse base frame online therefore makes a lot of sense, in that the seller will typically deliver it right to your door ready for you to build. 

Additional Help – Having constructed a few greenhouse bases from kits over the years let me assure you that while they’re easy to construct, it’s a whole lot easier if you have someone to help you. When it comes to moving the completed base into position, for example, two sets of hands are definitely better than one. 

Greenhouse Base Foundations

Plastic Grids or Tiles – Plastic grid tiles are a relatively new entrant into the greenhouse base industry. Their plastic construction actually has a whole load of benefits which makes them ideal. Indeed, having weighed up all the options for my own greenhouse I actually opted for these plastic tiles myself. 

For starters these plastic tiles are much lighter than paving slabs. Even the strongest of us can start to feel the twinges after a day spent bending over moving concrete paving slabs. Plastic tiles make preparing the area of your greenhouse a far easier and more pleasant job.

Being plastic they’re rot-resistant even in the worst weather and won’t be easily damaged if you’re unfortunate-enough to drop a plant pot or tool on them. The same could not necessarily be said of traditional paving slabs. 

Lastly these plastic tiles are easy to cut – if necessary – with a saw. This means that they can be used easily to create a base even for an unusually-sized greenhouse. 

Paving Slabs – Paving slabs are probably the “classic” way of preparing the ground for your greenhouse. You have a number of options here. Most notably you could construct a rectangle of slabs onto which your greenhouse fits neatly, or pave a whole area and place the greenhouse on top. 

Paving slabs can be attractive and hard-wearing, but they’re also heavy to work with and great care must be taken not to damage the slabs themselves or your fingers when laying.

Lastly, if you are considering using paving slabs as a greenhouse base then also consider how you’ll attach your greenhouse firmly to it. Simply resting the greenhouse on top is unlikely to be the most secure method. Instead you may want to use a masonry drill bit to create some holes through which you can pass fixtures for your greenhouse.

Concrete – Digging out some earth and laying a solid concrete base can be very effective, if you are DIY-minded or are willing to pay an expert to install it. If self-installing it is crucial that you check the levels to ensure they are right-on. 

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