A conservatory built under 30 square meters and separate from the main house does not require building regulations. Therefore, technically, foundations are not a requirement.
Before you think it’s okay to go ahead without foundations, consider that any construction needs to be built on a solid, level, damp-proof footing to ensure stability and durability. We never recommend building a conservatory without foundations.
Many conservatories are now built with open access to the house or with integrated heating systems. This means they fall under the same bracket as an extension for permitted development rights and Building Regulations. Under Building Regulations, an extension does need the correct foundations.
How important are conservatory foundations?
Foundations for a conservatory are essential. Your conservatory structure will only be as strong as its foundations and without the correct preparation, groundwork and footings, it could start to subside.
If you’re constructing even a small lean-to conservatory, we would not recommend you build without making sufficient preparation of the ground and footings.
We require conservatory foundations prepared for all our conservatories (to help you, we provide specifications of foundation requirements for your builder, see below).
Why do conservatories need foundations or footings?
A conservatory might look deceptively light because it’s made out of glass, but the weight of the glass needs considerable support to evenly transfer the weight into the ground.
Whatever type of soil you are building on is prone to shifting under different conditions. Under normal conditions, the ground swells and contracts on a constant basis. Throw in heavy rain and frost and this can significantly destabilise the ground.
Foundations apply a stable base to a structure to ensure that the ground isn’t constantly shifting and that the structure is safe to live in.
How deep should footings be for a conservatory?
There isn’t a specific minimum depth for conservatory foundations as they are dependent on the ground conditions and the size of the structure. A small uPVC conservatory will not require footing to be as deep as a large orangery style brick-based structure.
On average, standard conservatory foundations (with no obstructions) should be at least a metre (1,000mm) deep for a small lean-to, or 1500mm for a more sturdy structure - such as an orangery or large conservatory with brick walls. The width of the trench is variable.
For traditional extensions (that carry more weight), there is a general rule that foundations should be at least as deep as the distance from the front of the wall, to the edge of the foundation. But, no less than 1500mm deep.
Don’t forget, the depth of your foundations will dictate the maximum weight of your construction. This means that if you ever wanted to build a solid roof on your conservatory, or make your conservatory more solid with brick walls, your foundations could restrict you. It’s always better to future-proof your foundations during construction.
To calculate the actual regulatory depth and width, your local Building Regulations office will need to be involved with this (or a registered installer will do this for you). They will take into consideration the load weight that the structure will place on the ground and other ground conditions, such as the proximity of trees, rivers and train lines.
Never start work on a conservatory without first speaking to your local authority about building regulations. Or, use a registered installer that will do this on your behalf.
Always get a second opinion if an installer tells you that you don’t need foundations at all.