Insulating Below Suspended Timber Floors

Insulating below suspended timber floors

Reducing heat conduction in timber floors is important for insulation, and is possible by adding insulation between the timber joists, under the timber floor deck. Using this type of added insulation can improve existing timber floors and can also be used for new timber floors. Insulation boards are particularly suitable for extensions as they are easy to add, and can match new floor levels to existing.

The properties of Ballytherm Insulation match those required for this application. The insulation provides support to timber floors. It has a low rate of heat conduction, so a reduced thicknessof insulation material can be used between joists in timber decks.

The installation method used to install the foil insulation Ballytherm boards is as follows:

The boards are inserted on the side of the joist or on battens. They can be inserted under the timber deck, allowing no air gap, or they can be inserted at the bottom of the joists allowing gaps between the timber deck and the Ballytherm boards.

If the boards are installed allowing gaps, the tiny air spaces will reduce the level of heat loss emitted by the radiation from the reflective property of the Ballytherm boards. This will add to the thermal insulation property of the timber floor.

Table 7 indicates the thickness needed in Ballytherm Insulation to meet regulations.

Table 7

Further Advice & Information

For more information about Ballytherm products, technical advice, or guidance on the suitability of our products for your project, contact us at 0800 644 6900,, email us at or use our contact form.

Floor Insulation

Design Guidance