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DELTA Separation Layers


Vapor permeable underlayment with structured separation and drainage layer for ventilated and non-ventilated pitched roofs and facades with metal cladding.


The 8mm high randomly oriented studded fibre mat ensures a permanent swirling of air around the underside of the metal roof panels. As a drainage course, the studded structure reliably channels any moisture to the exterior. Rattling noise of rain or hail is reduced by up to 15 dB.


Vapor permeable roof underlayment based on DELTA®-VENT S, thermally bonded to a randomly oriented polypropylene fiber mat with studded structure.

Included with every roll is a package of 120 DELTA®-SEALING NAILS.


DELTA®-TRELA is installed parallel to the eaves with the studded structure facing upwards. The next course of membrane is overlapped in shingled fashion, ensuring that water is shed to the outside. The studded texture provides a non-slip surface. The underlayment is water and rainproof. DELTA®-TRELA with DELTA® Sealing Nails can also be used as an installation work cover. Applying DELTA®-TRELA in one step is much faster and easier than applying an underlayment and a separation layer in separate steps, saving time and money in project schedules.

Technical Data

Product name DELTA®-TRELA
Color dark gray / black
Water vapor transmission 820 g/m ²/24 h
472 g/m ²/24 h
ASTM E96-05, Proc. A
ASTM E96-05, Proc. B

69 perms [grains/h/ft ²/in Hg]

120 perms [grains/h/ft ²/in Hg]

ASTM E96-05, Proc. A
ASTM E96-05, Proc. B
Fire characteristics Fire resistance: Class B2 DIN 4102
Structured separation layer height apprx. 0.3 in ( 8 mm)
Temperature range -40 °F to +176 °F (-40 °C to +80 °C)
UV exposure

Always cover as soon as possible. Maximum exposure 6 weeks.

Weight apprx. 270 g/m²
Roll weight apprx. 37 lbs (17 kg)
Roll size 98' x 3' 3" (30 m x 1 m)
Fasteners (included) DELTA® -SEALING NAIL 1 package (120 nails)

DELTA® is a registered trademark of Ewald Dörken AG, Herdecke, Germany.
Incorporate DELTA® Products into your plans quickly and easily by downloading our design files from

More Information

Overview Adhesives


Incorporate DELTA Products into your plans quickly and easily by downloading our design files from