Ground floor – insulation below concrete slab

Ground floor – insulation below concrete slab

Thermal insulation is usually installed below the floor slab in buildings featuring continuous, low-level heating. It helps make effective use of the thermal mass of the concrete slab, rather than repeatedly warming it and allowing it to cool.

For the floors of industrial buildings and some commercial buildings, the concrete slab also often acts as the hard-wearing, non-decorative floor finish, meaning the only available position for insulation is below the slab.

What Polyfoam XPS products are suitable below a concrete floor slab?

Most domestic projects use a floating floor arrangement, with insulation installed above the floor slab or suspended floor deck, and below a screed or board covering. If a below slab arrangement is desirable, however, Polyfoam Floorboard Standard will adequately bear the imposed loads.

For commercial or industrial buildings, Polyfoam Floorboard Extra or Polyfoam Floorboard Super provide the necessary thermal performance and superior compressive strength performance, depending on the requirements of the project.

Polyfoam XPS Ltd is a leading manufacturer of closed cell, extruded polystyrene insulation. The Polyfoam range is lightweight, strong, moisture resistant and easy to cut and shape, providing thermal performance and strength for the lifetime of the building. Product benefits include:

  • High compressive strength.
  • Highly resistant to water absorption.
  • Robust and suitable for use in highly loaded floors
  • Long term dimensional stability.
  • British Board of Agrément certificate.
  • Environmental Product Declaration.
  • BES 6001: Responsible Sourcing of Construction Products.

Why is extruded polystyrene (XPS) insulation suitable for laying on the ground?

Many insulation products, when installed below the ground floor slab, must be laid above the damp proof membrane (DPM) to protect them from ground water. A separating layer is then required over the insulation layer to protect it from the concrete slab.

Extruded polystyrene (XPS) is unique among widely-available thermal insulation materials for its tolerance of damp or wet environments. That means it can be laid directly on prepared ground, with the DPM laid over it also acting as the separating layer between insulation and concrete – a saving of both time and membrane material.

The superior load-bearing performance of XPS lends itself to the demands of storage/racking and vehicle movements in warehousing and other industrial environments. It can also be used below raft slabs in residential and other low-rise buildings, offering the opportunity to enclose the entire fabric within the thermal envelope, reduce linear thermal bridging at junctions between construction elements, and achieve a greater level of building performance, comfort and energy efficiency.

Recommended Polyfoam XPS products for below floor slab applications are: