Non-Breathable Roof Underlay

  • Non-breathable
  • High tensile and tear strength
  • Clean and easy to handle
  • Durable
  • UV resistant
  • BBA approved
  • Lightweight alternative to traditional IF
  • Integrated tape for sealing laps
  • Guidance lines for minimum laps


Marley Universal non-breathable underlay is a lightweight (116g/m²), high-performance membrane for pitched roofs. Supplied in 1m x 45cm rolls with integrated tape for sealing laps, the underlay is fully compliant with BS 5534 and suitable for all UK wind zones 1 - 5.

Marley underlays are manufactured using the latest materials and processes, and each incorporates a number of useful features that assist in ensuring installation that is not only correct, but also compliant with the latest British Standards.

Function & Compatibility

Universal non-breathable underlay is designed to integrate seamlessly within a full Marley roof system and is suitable for roofs with traditional ventilation products or ventilated batten cavities.
Technical data

 Material  PP 3 layers
Weight  116 (-10+10)
Resistance to water penetration  W1

Batten gauge

<250 (Zone 1-5)

<354 (Zone 1-5)

Adhesive tapes  1
Tests  CE, BBA, IBA approved
Tensile strength (N/50mm)  
Before artificial aging

 MD 280 (-70)

CMD 170 (-50)

After artificial aging


 MD 240 (-70)

CMD 140 (-50)

Elongation (%)  
Before artificial aging

 MD 60 (-20)%

CMD 70 (-20)%

After artificial aging

 MD 40 (-20)%

CMD 50 (-20)%

Tear resistance


 MD 140 (-40)

CMD 130 (-40)

Flexibility at low temperature  -40oC
Equivalent air layer thickness (Sd)  15
 Reaction to fire  Class E

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