How and where to use guide
VELUX Vapour Barrier 55x118cm BBX CK06 0000
Typical applications and positioning
This vapour barrier is designed for installation within pitched and flat roof assemblies where moisture control is critical. It is suitable for new build construction and refurbishment work on residential and light commercial properties. The membrane should be installed on the warm side of the insulation layer, typically between the insulation and the internal plasterboard or ceiling finish, to prevent warm moist air from the building interior reaching cold surfaces where condensation would form.
- Pitched roof assemblies with timber rafters and insulation
- Flat roof constructions with insulation layers
- Refurbishment projects upgrading existing roof insulation
- New build residential and light commercial roofing
Installation and on-site practice
Install the vapour barrier as a continuous layer, ensuring all joints and seams are properly sealed to maintain the integrity of the barrier. The membrane should be laid flat without creases or tears, and any penetrations for services must be sealed. Always confirm the product dimensions (55 × 118cm) match your roof panel or section size before ordering, and follow current site practice and building regulations for vapour barrier installation. Ensure adequate ventilation is maintained on the cold side of the insulation to allow any residual moisture to escape.
- Lay membrane flat and smooth to avoid wrinkles or damage
- Seal all joints and seams with appropriate tape or sealant
- Seal around any service penetrations
- Maintain ventilation on the cold side of insulation
- Check dimensions against your specific roof panel requirements
Performance and limitations
The 0.5mm polyethylene construction provides reliable vapour barrier performance in demanding roofing applications. However, this product is a vapour barrier component only and must be part of a complete, properly designed roof build-up. It does not provide weatherproofing, structural support, or thermal insulation on its own. Performance depends on correct installation as a continuous layer; any gaps, tears, or poorly sealed joints will compromise effectiveness and allow moisture penetration.
- Vapour barrier function only; requires complete roof assembly design
- Does not provide weatherproofing or structural support
- Effectiveness depends on continuous, sealed installation
- Tears or gaps will allow moisture transmission
Storage and handling
Store the vapour barrier in dry conditions on site to prevent damage before installation. Protect from direct sunlight and weather exposure. Handle carefully to avoid punctures or tears that would compromise the barrier function. Keep the product in its original packaging until ready to install, and confirm grade and dimensions match your project specification before opening.
- Store in dry conditions away from weather and direct sunlight
- Protect from punctures and tears during handling
- Keep in original packaging until installation
- Verify product grade and dimensions before use