How to install insulation before floor screeding

These days, many houses have ground floors constructed of solid concrete instead of suspended timber construction. When this needs to be replaced, it can be insulated to save the householder money and cut down on energy consumption.

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There are several options for insulating before you apply a floor screed. There are products such as rigid board insulation and flexible foam insulation materials. It is important to select the right product for your construction project and install it correctly.

In general, insulation is laid after the floor base but before the screed. This is sometimes referred to as a floating type of screed construction. Correct installation is essential if the insulating properties are going to work correctly.

Choosing a rigid or flexible installation

According to the Energy Saving Trust, insulating a ground floor can be a cost-effective energy-saving measure and could save a householder up to £65 a year, so it is important to choose the correct product.

To lay rigid board insulation panels, you will need a level floor base. This means that pre-cast floors will probably have to be levelled with a levelling compound to get rid of steps and sharp protrusions. In domestic projects, a thin layer of sharp sand will probably be adequate.

Flexible insulation is more forgiving because materials such as expanded polyether foam and mineral wool quilt are flexile enough to mould around uneven surfaces. However, it is still important to make the base as even as possible.

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Installation tips for insulation

You can get floor screed mix from a supplier such as, but there are some preparation steps that you should carry out first.

If you are using a floating screed, you will need a damp-proof membrane over the base substrate prior to the insulation layer. The membrane sheets need to cover all abutments and must be taped at the joints.

The insulation is then laid by commencing with 25cm thick perimeter strips at the external walls. The boards must be staggered and taped down.

Special care is needed around service pipe openings and abutments or columns. Check that all of the internal and external corners are taped down tightly.

Where there is no pre-laminated membrane on rigid insulation, a layer of 500 gauge polythene will need to be applied for adequate protection.