Types of floor insulation and where they are used: A jargon busting guide

19 March 2019 Kingspan Insulation UK

An area of the building envelope which is often overlooked when improving the insulation of a building is the floor. Cold floors are not seen as a priority to insulate but adding insulation can help save money in fuel bills, save carbon and create a more comfortable environment. In a domestic dwelling, the ground floor, and any floor that is above an unheated space, such as a garage, would benefit from being insulated. The type of floor, and how it can be insulated depends on several factors and there are a range different floor types, each of which should be insulated in a different way. To help understand some of the different possibilities, we’ve created this guide to some of the key terms used when discussing floor insulation. 

Floor Constructions


Solid concrete floor

A solid concrete floor is usually constructed of a concrete slab, with a damp-proof membrane and screed on top. Older buildings (pre 2000) with a solid floor, rarely had insulation installed (much older floors may not even have a damp proof membrane). When insulation is present it may have been installed either below the slab or below the screed. This is particularly important with underfloor heating – for more information on this topic please see our article on underfloor heating.


Beam and block floor

Beam and block floors are ones where the floor is constructed with reinforced beams being laid between the walls and the space between the beams infilled with typically concrete blocks (often aircrete for better thermal performance), rather than a concrete slab. Insulation, if present, will usually have been laid above the beam and block floor and below the floor screed.


Suspended timber floor

A suspended timber floor is one made from timber floorboards which are attached to joists (usually wooden). This construction is commoner in older houses (pre 1940s). There is usually a void beneath the joists and the insulation will sit between the floor joists. Depending on the available access to this void space below, insulation can either be added from below the joints, (for example if there was a basement below the floor to the insulation), or by lifting the floorboards and insulating between the joists from above.

Suspended concrete floor

A suspended concrete floor is where a solid concrete slab, (either formed in situ or precast), has a perimeter, or at least two of its opposite edges, supported on walls, beams or columns that carry its self-weight and imposed loading. It can also be formed by an concrete slab being poured over a profiled metal deck.

Other flooring terms

A floating floor

Floating Floor

A floating floor is one which is not fixed to the layer beneath it i.e. it floats on top. It’s an installation method rather than an actual floor type. This is usually finished with interlocking chipboard, gypsum or cement fibre boards, or a laminate covering. See our article on why and how to construct a floating floor for more details.

A non-floating floor is one that is fixed to the layer beneath it.

Kingspan GreenGuard_Floors High - Concrete_UK

Heavy duty floor

A heavy duty floor is one which will be expected to take a higher service load, such as for heavy duty commercial, industrial and cold store flooring. For this insulation with a high compressive strength is needed. This often comes in variety of grades to suit a range of service loads.



A soffit is the underside of an architectural component, for example an arch, beam, staircase or underneath car park decks, where a concrete floor might be supported by concrete or steel beams and columns.

Kingspan GreenGuard_Basement_UK

Basement floors

There are extra considerations when insulating a basement floor. As a basement is usually surrounded by earth, if the insulation is being placed externally to the damp proof membrane, it is important that the insulation is resistant to the passage of moisture.When calculating the thickness of insulation required to meet the target U-value, the size and height of the basement are key.

More information

For details about the flooring products which are available from Kingspan, please visit our flooring applications page. If you know what product you want, our u-value calculator can help you work out what thickness you need, and for guidance on installing floor insulation in several applications please see our how to videos.