Building a greenhouse foundation – instructions and hints

When building a greenhouse, the right foundation is the basis. It not only ensures a safe stand, it also protects against ground frost.

Greenhouse - Laying the foundation
© Sonja Birkelbach –

The greenhouse should remain in the garden all year round and not only accommodate plants, but also defy wind and weather? Then a solid construction is the prerequisite. The hobby gardener creates the basis for this with a solid foundation. In the following we will tell you why the foundation is so important for greenhouses and what possibilities there are to lay a foundation yourself.

Why are foundations so important?

This question can be answered in one sentence: A foundation prevents your new greenhouse from collapsing like a house of cards in strong winds and storms. With the foundation you create a load-bearing substructure which ensures the stability of the greenhouse in all weather conditions. The foundation has many functions. The structure must be able to withstand its own load and the weight of the greenhouse on which it rests. It must not happen that the foundation continues to drill into the ground because the pressure exerted on the foundation is simply too great.

Tip: A foundation also protects against unnecessary loss of heat from the ground and the ability to maintain the temperature in the greenhouse.

Does every greenhouse need a foundation?

Massive greenhouse constructions always require a foundation. A foundation can only be dispensed with if the greenhouses are small greenhouses made of foil, which are only set up during the summer. To ensure that the greenhouse still has a secure footing and does not lift off during the first gust of wind, it is important that the pipes over which the foil is usually stretched are securely fastened to the ground with ground anchors. Simple small greenhouses can also be weighted down with bricks or the like or you can tie the pipes to fences or walls.

Various foundations

First of all, you have to decide whether you want to buy a prefabricated set from a specialist dealer or build your own small greenhouse. Finished sets are usually supplied with a matching wooden or metal frame, which acts as a foundation. When assembling on site, you should observe the enclosed instructions and attach great importance to statics and safety.

If you want to build your own greenhouse, you have the choice between different foundations:

  • wooden beam foundation
  • Frame made of metal tubes with ground anchors
  • Pouring the floor area with concrete
  • Concrete strip foundation
  • point foundation

Which foundation should I choose?

Wooden foundation on point foundation
© dmitrypk –

Of course, this is up to you. Point foundations are usually used for the construction of greenhouses. Metal foundations are usually too costly for the construction of greenhouses. You also have the option of erecting the foundation partly from wood. This will be discussed in more detail below.

The foundation is intended to ensure that your new greenhouse stands securely and can withstand storms and rain. Important criteria for choosing the right foundation are the size and weight of the greenhouse. In addition, the planned use also plays a role.

Tip: Larger greenhouses often require a building permit.

The foundation of the foundation forms the solid basis for the later greenhouse. Therefore, work carefully and adhere to the respective dimensions. The foundation must appear straight and right-angled. Also make sure that the surface is level and smooth.

Laying the foundation yourself

A solid foundation can be created by building a strip foundation or pouring the foundation with the help of fabric mats and formwork boards. First you have to dig a trench. This trench was supposed to be a depth of at least 80 cm so that the frost cannot work and the foundation does not rise as a result. After you have concreted or bricked the foundation, fill the recess with earth and attach the foundation frame.

What dimensions does my foundation need?

The dimensions of the foundation will certainly vary. No compromises should be made regarding depth. We’ve already heard of Minimum depth of 80 cm I spoke to him. In the low mountain ranges and other less climatically favoured regions, however, the frost can work its way up to 1.5 metres into the ground and cause damage accordingly.

Tip: A foundation depth of just over a metre is a good alternative for all climatic conditions in our latitudes.

The dimensions of the foundation will ultimately depend on the size of the greenhouse. The weight of your new greenhouse determines the strength of the foundation.

Why does a foundation need a gravel layer?

A gravel layer under the actual foundation offers you additional safety. The ballast should be at least ten centimetres deep, with slab foundations the same thickness can be chosen as for the foundation itself. The water can drain better through the gravel layer. This makes sense especially if you have floors that are difficult to drain. Here there is the danger of stagnant moisture and stagnant moisture is tolerated by very few plants.

What is important when constructing a concrete foundation?

work stage Description of the
surveying The exact measurement of the foundation is decisive for the later status of the greenhouse.
The best way to do this is to make a string framework and mark out the corresponding area exactly.
Dig a trench The trench must be at least 80 cm deep.
In areas with a harsher climate, depths of 1.20 metres make sense.
A trench is important to prevent moisture from reaching the greenhouse material and endangering its stability.
Inserting concrete pipes If a point foundation is to accommodate posts and supports, concrete pipes are left in the ground for this purpose.
Here, too, the measurement must be accurate.
Use a spirit level before filling the concrete into the pipes.
Casting concrete foundation Concrete foundations can be bricked or cast from concrete slabs.
Whether a concrete foundation really offers stability is often dependent on the dowels and screws you use for fixing.
Larger greenhouses require a concrete strip foundation.

Wooden foundation as an alternative to concrete foundation

Foundations are generally made of concrete, but you can also use some wood. The foundation consists of a wooden frame made of squared lumber. The frame is additionally provided with longitudinal and transverse struts. The wooden frame is finally applied to point foundations.

What is a point foundation?

A point foundation can be used to hold your wooden frame and anchor it securely to the ground. Anchor shoes are cast into the foundations for this purpose. There the squared lumber of the wooden frame can be fastened later. Point foundations are an inexpensive alternative to slab foundations. Furthermore, an optimal heat exchange is ensured. The moisture does not accumulate, but can dry well due to the distance between the floor scar and the wooden foundation.

Creating a point foundation – step by step

  1. drill holes
  2. Mounting the foundation frame
  3. Fill holes with concrete
  4. Align the foundation frame precisely

Don Burke

I am Don Burke, one of the authors at My Garden Guide.  I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts

link to Pin Oak Tree

Pin Oak Tree

Pin Oak Tree (Quercus palustris) The pin oak tree (Quercus palustris) is a plant from the genus of oak trees in the family of the beech plants (Fagaceae). In temperate latitudes, it...