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OMEGA UDOs 330 TopGrip Roof Underlay

OMEGA UDOs 330  TopGrip Roof Underlay
Vapour-permeable and weldable membrane for underroofs with increased rainproofing in accordance with ÖNORM B 4119. Carries the Swiss seal of approval for underroof membranes for building envelopes.
  • weather-proof for 12 months’ exposure
  • for roof pitch from 1.5° (seam-welding)
  • for roof pitch from 5° (SK DUO)
  • anti-slip fleece surface

Available dimensions

Article number Type Roll width Roll length Rolls / Pallet Total area Inquiry List
2TOP SK DUO 1.5 m 30 m 20 rolls 900 m²

Field of application

  • for vented pitched roofs
  • minimum roof pitch 1.5° (seam-welding)
  • minimum roof pitch 5° (SK DUO)
  • for installation directly on the thermal insulation / wood sheathing


  • anti-slip fleece surface
  • rain-tight
  • air-tight
  • 12 months UV light-resistant
  • can be weldes
  • water-tight
  • easy to bond (SK DUO)

Product data

Is a vapour-permeable, weldable roofing membrane for laying directly on thermal insulation or wooden sheathing. The membrane is suitable for underroofs with increased rainproofing in accordance with ÖNORM B 4119 and corresponds with the classification UDB-A in compliance with the ZVDH (national Association of Roofers) standard. Can be used for extreme demands in accordance with the underroof category pursuant to SIA 232/1. Moisture in the building’s interior can escape to the outside in the form of water vapour through the underroof membrane, at the same time providing tightness against wind-driven rain. Complies with the Swiss ‘Gebäudehülle Schweiz’ (building envelope) seal of approval for underroofs.
Material composition
PES fleece with TPU layer on both sides, including fleece coating on top
1 mm
Light grey
420 g/m²
Weight per unit area
0.25 m
Temperature resistance
-40 °C
Temperature resistance
100 °C
12 months
Resistance to water flow
Resistance to water flow
EN 1928
Elongation - lengthwise
50 % (± 40)
Elongation - crosswise
60 % (± 40)
EN 12311-1
Tensile strength - lengthwise
420 (± 80) N/50 mm
Tensile strength - crosswise
430 (± 80) N/50 mm
Tensile strength
EN 12311 - 1
Tear propagation resistance - lengthwise
280 (± 80) N
Tear propagation resistance - crosswise
320 (± 80) N
Tear propagation resistance
EN 12310-1
Cool and dry
Fire performance
Fire performance
EN 13501-1 / EN 11925-0

Processing guideline

(1) UNDERLAY (unsupported)

OMEGA roof Underlay is nailed parallel to the eaves with a slight drape and laid and mechanically fixed above the rafters. Vertical overlaps/joins must always lie on a rafter.
Glue all overlaps/connections with OMEGA N55 adhesive, or weld using a heat gun or OMEGA QSM solvent welding agent.
(1) UNDERLAY (unsupported)

(2) Underlay (supported)

OMEGA UDOs 330 Roof Underlay is laid on sheathing parallel to the eaves. The blankets are fixed with concealed nails spaced at 10 cm at the ridge-side edges (marks at edge). All overlaps/joins must be bonded with OMEGA N55 Adhesive or to weld using hot air gun. For the raintight version (temporary cover) a nail-seal under the counter batten (OMEGA NDB Nail Sealing Tape DSK) is necessary.
In accordance with the SIA standard 232, the ZVDH data sheet and ÖNORM B 4119, in case of increased requirements, the counter-battens must always be sealed with Isocell nail seals, e.g. with the OMEGA Nail Sealing Tape or, from a roof pitch of ≥ 5°, with the PE NDB Nail Sealing Tape DSK. The use of corrosion-resistant fasteners is recommended.
(2) Underlay (supported)


We recommend an eaves construction with drainage below the gutter so that snowmelt build-up can easily drain off. We recommend the use of a metal sheet to drain off water.


The ridge area is closed directly when covered with OMEGA roof underlay. This provides immediate protection against water penetration. In non-insulated lofts and/or ventilated interior insulation the ridge formation must be made open: the blankets end 3 cm before the ridge apex, counter battens are mounted and a
50 cm wide strip of OMEGA roof underlay must be attached over the roof apex.


The first step in valley formation is to lay a continuous valley blanket.


Sections cut out for roof penetrations (extractor pipes, roof windows, chimneys, etc.) should be kept as small as possible and the ends of the sheets must be fixed so that no rain or snow can penetrate. To achieve a perfect seal the suitable adhesive technology by ISOCELL GmbH & Co KG must be used.
Make sure that the substrate is clean! The manufacturer can accept no liability for mechanical damage. The applicable regulations and guidelines (e.g. of the ZVDH (Central Association of German Roofers) for Germany, Austrian Standard, ÖNORM B 4119, for Austria, ...) must be observed!
The minimum joint width must be 4 cm according to ÖNORM B 4119.
The roof underlay does not replace roof covering. The roofing membrane is to be fixed with battens. In general, cross joints and lock seams are to be avoided.
Welding temperature approx. 260 to 280 °C, depending on the ambient temperature. (Test welding is recommended).
Please note the guidelines for installation of the OMEGA UDOs 330 Roof Underlay!