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Vapour Permeable

Protect VP400

Protect VP400 PLUS LR is a highly vapour permeable roof underlay.

It offers the lowest vapour resistance of any Type LR roofing underlay in its class, and yet it remains completely airtight. It is suitable for use in all pitched roofs. As the airtightness of buildings and dwellings continues to improve due to better workmanship and new practices, it is ill advised to allow uncontrolled air movement within the structure, including through a roof underlay in roofs with no vapour control or air barrier layers.

One of the primary functions of roof underlays is to help manage the wind load pressures on the roof. In order to achieve this the underlay should have sufficient mechanical properties to be able to deflect the wind load pressures safely over the structure. Another essential property is that the underlay be water and air tight. Air permeable underlays allow air to penetrate the membrane making it much more difficult to withstand the maximum wind load pressures and driving rain without other surface treatments.


  • Highly vapour permeable, but completely airtight.
  • Completely watertight >7.0m water resistance.
  • Strongest underlay in its class/weight range.
  • UV and heat resistant.
  • Tough and durable.
  • Can be used as temporary roof covering.
  • Has ‘unrestricted’ use for wind uplift in all exposure conditions in the UK and Ireland.
  • BMTRADA Independently certified.
  • Helps to avoid condensation risk in the roof space in accordance with BS 5250 and NHBC requirements.

Protect VP300

Protect VP300 is a medium weight vapour permeable roof underlay with a vapour resistance better than that required by BS 5250 and a strength greater than many other underlays in its class.

It is suitable for all pitched roofs particularly fully supported applications. Protect VP300 is both CE marked and BM TRADA certified and provides an economic solution when the highest specification of roof underlay such as VP400 Plus LR is not required.

Protect VP300 can provide a secondary line of defence against wind driven rain and snow, the reduction in wind uplift loads on the roof covering and is also able to be used as a temporary roof covering before the slates or tiles are applied.


  • Vapour permeable with a performance better than required in BS 5250.
  • Completely watertight providing at least 2.0m in water resistance.
  • Good all round performance for its weight and one of the best in its class.
  • UV and heat resistant.
  • Tough and durable.
  • Can be used as a temporary roof covering.
  • BMTRADA Independently certified.
  • Helps to avoid condensation risk.