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All You Need to Know About Greenhouse Foundation & Flooring

Glass greenhouse on a foundation made of bricks and soil flooring with the text: All you need to know about greenhouse foundation & flooring

Table of Contents

Foundation. Footer. Flooring. They all start with F. And they all mean similar things. Most people are wondering what type of foundation is the best choice and what they need to do in terms of ground preparation.

“Do I need to build a foundation for the greenhouse?”, is the big question that we get asked from our customers frequently. Maybe you have been wondering the same and that’s why you are here. So, let’s not waste time! Let’s start talking about greenhouse foundation, flooring, and ground preparation for greenhouses.

Why you shouldn’t overlook the importance of a great foundation

The foundation is the whole system on which the greenhouse is set up. There are different options to choose from. Whatever type you’re going with, they all have one thing in common, though: it needs to be level. You should not rush this. Take your time in preparing the ground before setting up the greenhouse!

More stability & security: Even if your greenhouse is well-built. If you don’t put it on a level and secure foundation, it won’t be as stable when it’s stormy. You don’t have many storms where you live? Well, you should anchor it down still because you never know if you will have storms in 5-15 years from now.

More durability: Greenhouse kits are built to be placed on a level foundation. They will last longer when you set them up this way because all parts are where they need to go.

Easier assembly: In addition to the previous, a level foundation makes assembly easier because they are designed for level grounds.

Less hassle & work overtime: If you do it right the first time, you don’t have to renew the foundation after 10 years or so. It’ll make it a hassle-free garden structure for your precious plants.

Keeps the inside neat: If you prepare the ground properly and think about flooring materials, you won’t have any issues with drainage, water puddles, and algae or pests. Proper ground prep will avoid a bunch of issues in the long run.

Orangerie greenhouse on a stem wall foundation and a greenhouse with gravel flooring and the text: Tips for Building a Greenhouse Foundation

Types of greenhouse foundations

When we talk about greenhouse foundations, almost everyone has a different picture in mind. That’s why we need to go through these one by one. What you choose in the end depends on the type and size of your greenhouse, as well as soil condition. You should also check your building codes, etc. You may not be able to build something permanent without a permit.

Compacted soil foundation

This is the most basic type of greenhouse foundation you can go for. Some greenhouses come with certain base frames or anchors which prevent it from being uplifted. The ground has to be level so that the greenhouse isn’t crooked.

Greenhouse base frame buried in compacted soil as a greenhouse foundation
Base frame anchored in soil

This is not the strongest foundation but it will surely save you money. It is best for temporary greenhouses or those that are less than 8ft x 10ft (unless it comes with the proper foundation frame, such as Hoklartherm’s Riga greenhouses).

The weight of bigger greenhouses may cause glass breakage or warping of frames.

It is more difficult to level, unlike concrete. Yes, it will definitely save you more money but will cost you more time to maintain. 

Despite those mentioned setbacks, most gardeners prefer soil foundation because it has better drainage. This type of foundation lets the gardeners to conveniently plant in the ground. If you are concerned about the mess (i.e. mud), read the section about greenhouse flooring.

Pros

  • Good drainage
  • Easy setup without many tools & supplies
  • Cheap
  • May not need permit as it’s rather temporary

Cons

  • Only for small greenhouses or greenhouses with foundation frame
  • Not as secure when it comes to wind (unless it comes with a great base frame)
  • More difficult to level
  • More maintenance to keep soil level
  • May cause glass breakage if it isn’t level
  • May get messy unless you are using flooring as well

Slabs and decks

When we say slab or deck we mean a full foundation, where the greenhouse stands on. It covers the whole footprint of the greenhouse. This type of foundation is mostly used with concrete, stone, brick, or wood. It’s probably one of the easiest to walk on as everything is flat and quite even. No muddy puddles that you could have with soil.

Concrete

Glass greenhouse on a concrete slab as a greenhouse foundation
Concrete slab foundation

A lot of people think that concrete slabs are the best option, but that’s wrong. We never encourage customers to use a concrete slab for a hobby greenhouse. 

It’s expensive, it messes with the inside temperature, and it doesn’t allow for drainage. Greenhouses that are installed on concrete slabs generally are hotter in summer and colder in winter. 

Unless you add a drainage solution, the slab may become a little hazardous especially if you plan to use overhead irrigation. Depending on what water you are using, you might even get issues with algae where water stands for a while.

Pros

  • Good for larger greenhouses
  • Permanent & long-lasting level base
  • Relatively easy to build
  • Easier to keep it clean

Cons

  • Doesn’t allow drainage
  • Heat & cold sink
  • Expensive
  • May require a permit

Wooden deck

Gothic arch greenhouse (Riga XL 6) on a wooden platform
Greenhouse on a wooden platform or deck

Some people may think that wood is a better option because it’s a natural resource. This type of foundation is easy to clean and drains well. For added humidity, you can simply sprinkle some water on the floor. 

While this is nice, you still have a temperature problem. A deck doesn’t provide much insulation from below. There is air that can heat up or cool down the greenhouse undesirably.

Pros

  • Good for any size of greenhouse
  • Permanent & somewhat long-lasting level base
  • Relatively easy to build
  • Allows for drainage
  • Easier to keep it clean

Cons

  • Not good for insulation

Stone or brick paved foundation

Orangerie greenhouse on a paved foundation with bricks and a framed raised bed surrounding the greenhouse
Greenhouse on paved foundation

Maybe you want to use stone or a paved slab to match your garden paths. It surely looks prettier than a soil foundation.

The benefit of a paved foundation is the drainage. The cracks between the bricks, let the water run off. 

The material you choose can highly affect the temperature of your greenhouse within the seasons. Some stones contain heat and cold more than others. This means you really have to know the properties of your chosen material.

If you are more concerned about heating in winter than cooling in summer, certain stones contain the heat from the sun better. This can be an inexpensive way to heat the greenhouse.

If you are more concerned about cooling in summer (which really is the harder task), you want a rock inside that doesn’t absorb the heat as much.

Pros

  • Good for any size of greenhouse
  • Allows for drainage
  • Better insulation or temperature control
  • Permanent & long-lasting level base
  • Easier to keep it clean

Cons

  • Doesn’t allow drainage
  • Expensive
  • Requires more building skills
  • May require a permit

Footers, footings, and stem walls

These types of foundation have the same size and shape like the greenhouse but they are not filled in like a slab. They are basically just an outline that supports the greenhouse. Wood and concrete are most commonly used for footings.

Wooden footing

This is what we usually recommend the most as it is the most simple and inexpensive footer. You’ll see a lot of greenhouse foundations build like this.

Its main purpose is to provide level ground because it’s essentially a frame made of two layers of 2″ by 4″s.

Wooden footing under a hobby greenhouse on a lawn
Wooden footing

You probably ask yourself how you can make this foundation more secure. This mainly depends on the greenhouse you are purchasing. Some greenhouse kits, like the Monticello, come with ground anchors (see image below).

Ground anchor attached to a greenhouse on a wooden foundation
Ground anchor attached to the base of a greenhouse

For those who think that this doesn’t provide enough security because of the stormy weather you constantly have, you should probably go for a concrete footer instead.

Concrete footer

This is the more “advanced greenhouse foundation”. It does cost more but it will provide more security. It is basically a concrete base or wall in the ground (see image below).

Graphic that visualizes how a concrete footing for a greenhouse would look like
Concrete footing

This footer may require you to hire a constructor. It also may not work with every greenhouse kit, unless you can bolt the greenhouse to the concrete or set it in concrete (as shown in the image above).

Brick or cinder block footer

You can, of course, always use bricks or cinder blocks to build the greenhouse footer. This might be a good choice for heavier glass greenhouses. You can also match any bricks, retaining walls, or other things from your garden design.

Glass greenhouse on a foundation made of bricks and soil flooring
Janssens greenhouse on a brick footer

Stem walls

These types of foundations are not possible with all greenhouse kits. A stem wall lifts the greenhouse up, which creates more headroom. This also means that you have to drop the door. Otherwise, you would have an empty space at the entrance.

White orangerie greenhouse on a stem wall built with bricks
Orangerie on a stem wall

Greenhouse flooring

If you go for a footing made of concrete, wood, brick, or a compacted soil foundation, you want to think about the flooring as well.

The benefit of this method is drainage (in comparison to concrete slabs). In addition, you can pick a material that will serve best in your specific climate.

For example, if you are more concerned about the winter months, you can use gravel and rocks that have heat retaining properties.

Types of greenhouse flooring

Before we go through the different materials, we want to point out that it is recommended to use a weed barrier below the flooring. This can be a ground cover made of woven Polypropylene. If you want to do it the budget-friendly route, save up those newspapers. Put a few layers of the papers across the area and then add soil or gravel.

Gravel

This is what we usually recommend. It’s clean, easy to get, it’s somewhat easy to make it level, and it drains well.

The material you use depends on what you have available locally and for your budget. Most people go for any type of pea rock and then add some larger rock tiles for the path.

Flooring tiles

For more security and less mess, you can add some flooring tiles where you would walk and work the most. This may keep your greenhouse nice and clean.

You can use rock tiles or pre-manufactured lockable flooring tiles, such as these. Besides the surefootedness, they also allow water to drain quickly.

Photos of a started greenhouse foundation and a greenhouse on a stem wall with the text: How to build a proper greenhouse foundation

Tips for BEFORE you build your greenhouse foundation

There are a couple of things you should check on before you start building your greenhouse.

1. Check for building codes

First, check with your district’s officials and HOA if you need a permit for your project. There are also zoning requirements that have limited or specific types of foundations and other codes. Some zoning laws may even demand a licensed installation.

So, make sure you got all the necessary paperwork done BEFORE you start building.

2. Always wait for your greenhouse to arrive

Although we can send you a manual with the correct measurements, you should wait until you receive the greenhouse. This way, you can make sure your foundation fits the base frame/profiles.

We had it happen in the past, where people messed up the foundation because they had the foundation done before receiving their order.

3. Pick the right location

Make sure the location you picked is not right next to a tall tree. They will put a shadow onto your greenhouse, which consequently ends in less plant growth.

You also want to pick a spot that is not so windy if possible. It’ll make the assembly easier and protect your greenhouse from storms.

For the most sunlight, you want to face the long side of the greenhouse to the South or South-East. This way you will make the most out of the sun at any time of the year.

4. Examine the ground

Make sure to examine the soil condition on your preferred site. Some soils or grounds may need specific foundations. They may not have the strength or might have some characteristics that may create future difficulties.

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