40mm STEICOtherm Internal Wet Square Edge Wood-Fibre Insulation Slab - 1200mm x 380mm

40mm STEICOtherm Internal Wet is an ecological, vapour-open insulation board designed for applications where moisture management and thermal mass are critical. The Square Edge (SE) profile makes it particularly suitable for internal wall insulation (IWI) and floor systems where a tight, flush fit is required between slabs. The "Internal" designation refers to its specific dimensions and properties tailored for indoor handling and moisture safety. In the UK, many older solid-walled properties suffer from dampness if insulated with non-breathable materials. The STEICOtherm Internal Wet slab is considered the "safety-first" choice because its moisture-buffering capacity protects the original building fabric from rot and mould while significantly improving the U-value of the wall.

Each board features a square‑edge profile and two distinct faces:

• a lighter, machine‑sanded side, designed as the plaster‑carrying face, and
• a darker, untreated side, which faces inward during installation.

CHARCTERISTICS

• Fibres bonded using the wood’s own lignin - no synthetic resins.
• Ensures clean, precise installation.
• Light, sanded face for plaster; darker face untreated.
• Low thermal conductivity for improved energy efficiency.
• Vapour‑open and hygroscopic for healthy building physics.
• Dense structure reduces airborne sound transmission.
• Renewable wood fibres with low embodied carbon.
  
• Fully recyclable and resin‑free.

APPLICATION

• Solid Masonry Walls - This is its primary purpose. If you have an older property with solid brick or stone walls that has no cavity, this board is installed on the inner face of those external walls
• Timber Frame Linings - It can be fixed to the inside of a timber stud frame (across the face of the studs).
• Between and Under Rafters (Loft/Roof) - It provides a continuous layer of insulation that reduces "cold bridging" (heat escaping through the wooden rafters).
• Ceilings (Acoustic & Thermal) - It’s excellent at deadening the sound of footsteps or voices from the room above.

Note: Should not be installed outside, below the DPC and inside shower cubicles.

Regardless of where you install it on a wall, you should almost always use a full bed of lime adhesive behind the board. You want to avoid any air gaps between the board and the wall where condensation could hide.

CERTIFICATIONS