Roofing underlays — vapour-permeable, for pitched roofs
The roofing underlay goes on the outer side of the insulation, below the battens and the roof covering. It lets vapour out and protects the roof from above.
The roofing underlay is the layer below the tiles or the metal sheets: it is laid on the insulation, on the wood fibre boards or on timber boarding, with the counter battens and battens on top.
It has to be vapour-permeable so that moisture from the insulation can escape outwards. This is shown by the Sd value: the lower it is, the more easily vapour passes. The roofing underlays here have Sd values between 0.02 and 0.25 m.
When there is a tongue and groove naturheld board above the rafters and the pitch is at least 15°, the board itself is the rain-tight underlay and a membrane is optional. With a lower pitch, without a board above the rafters, or for renovation from outside, a membrane is laid.
Which roofing underlay where
| New roof, pitch ≥ 15°, tongue and groove board above the rafters | The board is the rain-tight underlay; naturheld LDB 0.02 optional. |
|---|---|
| New roof, pitch 10–15° | naturheld LDB 0.02 on top of the board. |
| Roof without a board above the rafters | naturheld LDB 0.02 over the rafters, or an OMEGA membrane on the insulation or the timber boarding. |
| Roof renovation from outside, without opening up the inside | naturheld LDB 0.02 over and between the rafters + board ≥ 35 mm. |
| Pitch from 5° | OMEGA MONOTOP 330 SK DUO — with two integrated adhesive strips. |
| Metal roof on timber boarding | OMEGA DRAINY PLUS — with a drainage mesh. |
The roofing underlays at a glance
The data come from the manufacturers’ technical data sheets; prices include VAT and are the same as on each product page.
| Product | Use | Sd value | Weight | Fire class | Price |
|---|---|---|---|---|---|
| naturheld LDB 0.02 | Renovation membrane (airtight) | 0.02 m | 170 g/m² | E (EN 13501-1), B2 (DIN 4102-1) | €4.64/m² incl. VAT |
| OMEGA UDOs 330 TopGrip | Roofing underlay, weldable | 0.25 m | 455 g/m² | E | €11.08/m² incl. VAT |
| OMEGA UDOs 330 | Roofing underlay, weldable | 0.18 (± 0.04) m | 330 (+ 5%) g/m² | E | from €9.47/m² incl. VAT |
| OMEGA MONOTOP 330 SK DUO | Roofing underlay | 0.12 (+0.05 / -0.04) m | 330 g/m² | E | €7.37/m² incl. VAT |
| OM 240 ND SK DUO | Roofing underlay | 0.15 (+0.05) m | 240 g/m² | E | €6.65/m² incl. VAT |
| OMEGA MONO 230 SK DUO | Roofing underlay, monolithic | 0.15 (+0.05) m | 230 (± 10) g/m² | E | from €5.30/m² incl. VAT |
| OMEGA MONO 200 | Roofing underlay, monolithic | 0.15 (± 0.1) m | 200 g/m² | E | from €4.30/m² incl. VAT |
| OMEGA 180 | Roofing underlay, three-layer | 0.025 (+ 0.035 / - 0.01) m | 180 (± 10) g/m² | E | from €3.19/m² incl. VAT |
| OMEGA LIGHT | Roofing underlay, lightweight | 0.025 (+ 0.035 / - 0.01) m | 145 (± 5) g/m² | E | from €2.35/m² incl. VAT |
| OMEGA DRAINY PLUS | Roofing underlay for metal roofing | 0.02 m | 450 (± 5 %) g/m² | E | €13.93/m² incl. VAT |
All roofing underlays
OMEGA UDOs 330 TopGrip
Vapour-permeable, weldable membrane for sub-roofs with increased rain-tightness, with a non-slip non-woven facing on both sides.
from €11.08 / m² incl. VAT →OMEGA UDOs 330
Vapour-permeable, weldable membrane for sub-roofs with increased rain-tightness to ÖNORM B 4119. Also supplied pre-welded to size.
from €9.47 / m² incl. VAT →OMEGA MONOTOP 330 SK DUO
Vapour-permeable membrane with two integrated adhesive strips for sub-roofs with increased rain-tightness — for pitches from 5°.
from €7.37 / m² incl. VAT →OM 240 ND SK DUO
Vapour-permeable roofing underlay for laying directly on thermal insulation or timber boarding, tested for tightness when perforated (ETA 25/0019).
from €6.65 / m² incl. VAT →OMEGA MONO 230 SK DUO
Monolithic vapour-permeable roofing underlay with increased UV resistance and resistance to driving rain. Also supplied pre-welded to size.
from €5.30 / m² incl. VAT →OMEGA MONO 200
Monolithic vapour-permeable roofing underlay for laying directly on thermal insulation or timber boarding; nail-tight to ÖNORM B 3647.
from €4.30 / m² incl. VAT →OMEGA 180
Three-layer vapour-permeable roofing underlay with a non-slip, tear-resistant surface.
from €3.19 / m² incl. VAT →OMEGA LIGHT
Lightweight three-layer vapour-permeable membrane for ventilated pitched roofs and for closed ventilated facades.
from €2.35 / m² incl. VAT →OMEGA DRAINY PLUS
Vapour-permeable membrane with a three-dimensional drainage mesh for laying on timber boarding under metal roofing; with an integrated butyl strip for the longitudinal joints.
from €13.93 / m² incl. VAT →Isocell photos and technical data: ISOCELL GmbH & Co KG.
See also
- Which roofing underlay to choose and how to install it
- Accessories for roofing underlays
- Insulation above the rafters with wood fibre boards
- The system: roof, wall and floor
- Vapour barriers
- All membranes and accessories
A quote for membranes and tapes
Send us the area and the construction — we reply with a quote for the membrane, the tapes and the quantities.