STEICOmulti UDB - Vapour-Open Roofing Underlay - 1.5m x 50m roll

STEICOmulti UDB is a highly vapour-permeable, 3-layer roofing and wall membrane. It is engineered to provide a secondary water-shedding layer and an airtight outer seal for roof and wall constructions. It is particularly effective when used in conjunction with blown-in wood-fibre insulation, as it is robust enough to handle high installation pressures. STEICOmulti UDB (the initials stand for Unterdeckbahn, or Underlayment) is the high-performance membrane designed for the outside of the building. It is the heavy-duty breather that keeps the wind and rain out while letting the structure breathe.

CHARCTERISTICS

• Extreme Vapour Permeability is its most critical feature. It is incredibly breathable, allowing moisture within the roof or wall to escape rapidly to the outside, which is vital for preventing rot in timber structures.
• Despite being breathable, it is completely watertight. It acts as a reliable secondary drainage layer, protecting the insulation and timber from any water that might get past the primary roof tiles or cladding.
• The 3-layer construction includes a protective fleece on both sides of a functional film. This makes it highly resistant to tearing and abrasion, even when installers are walking on the roof battens.
• It is UV-stable and weather-resistant, allowing it to serve as a temporary roof covering for up to 4 weeks (or more depending on specific site conditions) during the construction phase.
• When the overlaps are sealed, it forms a wind-tight outer layer that significantly improves the thermal efficiency of the insulation by preventing wind-washing.

APPLICATION

• Installed over the rafters or over rigid wood-fibre boards (like STEICOtherm) to provide a wind-tight and waterproof skin.
• Used on the outside of timber frame studs behind a ventilated rainscreen cladding system.
• Ideal for upgrading old roofs from the outside, providing a modern, high-performance alternative to traditional bitumen felts.

INSTALLATION

• When using STEICOmulti UDB on a roof, always ensure the membrane is draped slightly between the rafters (unless it is being laid over a rigid board).
• This creates a channel that allows any water to run down the centre of the membrane, well away from the timber rafters and the nail penetrations at the battens.