Conservatories May 22nd2017

How important are conservatory foundations?

Everest conservatory

Many people assume that, like windows and doors, conservatories can be installed from the ground up. But conservatories are more like an extension of your house, and need to have the same structural stability as any other building.

A conservatory is only ever as strong as its foundations – without the correct footings, it could start to subside. Even for a single storey conservatory or extension, you will need deep foundations to make sure it stands strong for years to come. This involves digging down to a considerable depth, and constructing a base made from a number of important elements.

Before digging out the foundations, check that your conservatory abides by planning permissions. Also, make sure your installer has the building skills required to construct a solid base.

Foundation depth

How deep you dig your conservatory foundations depends on many things. Soil conditions, and the proximity of trees, rivers and train lines all have a bearing on how the ground should be prepared before building on it. It’s also important to check for obstructions such as drain covers, which should be avoided. 

On average, we recommend digging at least a metre deep and filling the trench with concrete for maximum strength. Ideally, the depth would be closer to 1500mm, like a traditional extension. This is because more substantial materials are used in conservatory and orangery builds nowadays.

The brick cavity wall is built onto this base, and it should be insulated with 75mm of wall insulation.

Piled foundations

In loose soil conditions, it’s necessary to bypass this upper layer and reinforce the foundations by driving piles into the ground. These are steel rods that help distribute the weight of the conservatory evenly, for an unshakeable foundation.

Conservatory base

The conservatory base comprises a layer of 'hardcore' covered with a layer of sand. Hardcore is a solid material, like stone, that has been crushed and laid on top of a concrete foundation for a level base. At least 150mm of hardcore is recommended within your foundations. The compacted hardcore is then laid over with a bed of sand to provide an even surface.


A special layer of damp-proof material covers the base, to ensure that moisture from the ground does not rise up through the foundations.

Floor insulation

On top of the damp-proof membrane, a thick insulation layer is laid down to ensure that heat isn’t lost through the floor. We recommend using an insulation layer between 70mm and 100mm thick.

Smooth screed floor

A final layer of concrete is poured over the base and reinforced with steel, before applying the floor screed. Screed flooring is made from cement, or a mixture of sand and cement, and is ‘smoothed’ into place using a levelling board over a raised timber bed. 

This is the final layer before laying down tiles, wooden flooring or carpets, and it’s there to ensure a flat and smooth surface.

'How important are conservatory foundations?'

Get a FREE quote

To help provide you with an accurate quote simply fill in the form below and we will contact you to discuss your requirements.

Your details