50.5mm Insulation Board

The 50.5mm insulation board is a rigid PIR insulated plasterboard used to improve thermal performance from the internal side of a building. The 50.5mm depth comes from combining insulation with plasterboard. This makes it a space-saving option for internal upgrades, especially in refurbishment and retrofit work.

It is most often used in multi-layer build-ups or where tight manufacturing tolerances matter. For example, when boards need to slot into pre-set cavity depths without compression. This exact thickness is specified where design tolerances must be met with minimal trimming.

What is 50.5mm Thick Insulation Board?

The 50.5mm thickness insulation board is a composite panel with two attached layers:

• 38mm PIR insulation, and
• 12.5mm plasterboard facing the room

Together, these layers form a 50.5mm thick insulation board.

The PIR layer is the insulating element. PIR has a very low thermal conductivity – typically around 0.022W/m·K, which significantly restricts heat transfer. Closed gas-filled cells within the PIR reduce heat transfer by conduction and convection. The gas is encapsulated within a closed-cell structure, which is why PIR’s λ-value is so low.

The plasterboard layer provides a finished internal lining. However, it contributes little to the overall thermal resistance on its own.

The 50.5mm insulated plasterboard is rigid, and it is designed to fit tightly to minimise air gaps and thermal bridging, which is essential for maintaining performance.

What is 50.5mm Thin Insulation Board Used For?

A thin 50.5mm insulation board is mainly used for internal dry lining where both insulation and a finished surface are required. It can be used for:

• Dry lining solid masonry walls
• Sloping ceilings and dormer cheeks
• Timber frame or masonry walls lined internally
• Internal upgrades in refurbishment and retrofit projects

An insulation 50.5mm thickness board is specified when improving thermal performance must be balanced against losing internal space. Using insulation and plasterboard as one panel also reduces installation time and on-site handling.