Roofing underlay, particularly for using as roof cladding underlay and/or roof lining membrane

1. A roofing underlay comprising:

at least one outer nonwoven layer,

at least one inner nonwoven layer, and

at least one microporous membrane layer that includes at least one polyolefin plastic, wherein the microporous membrane layer is arranged between the outer nonwoven layer and the inner nonwoven layer,

wherein

at least one additional microporous membrane layer that includes polyolefin plastic is provided between the outer nonwoven layer and the inner nonwoven layer, and in that the additional microporous membrane layer is separated from the microporous membrane layer by a nonwoven separating layer, wherein the nonwoven separating layer is water-permeable, wherein the roofing underlay is water-tight and water vapor-permeable.

2. The roofing underlay according to claim 1 , wherein a plurality of additional membrane layers are provided, wherein adjacent microporous membrane layers are separated from each other by another separating layer.

3. The roofing underlay according to claim 1 , wherein one or more of the microporous membrane layer and the at least one additional microporous membrane layer comprises a material based on polypropylene (PP) and/or polyethylene (PE).

4. The roofing underlay according to claim 1 , wherein one or more of the microporous membrane layer and the at least one additional microporous membrane layer has a thickness in the range of 20 to 200 μm.

5. The roofing underlay according to claim 1 , wherein the at least one microporous membrane layer has a grammage between 15 and 150 g/m 2 .

6. The roofing underlay according to claim 1 , wherein the thickness of the at least on microporous membrane layer facing toward the outer nonwoven layer is between 50% and 200% greater than the thickness of the at least one additional microporous membrane layer facing toward the inner nonwoven layer.

7. The roofing underlay according to claim 1 , wherein the thickness of the at leak one additional microporous membrane layer facing toward the inner nonwoven layer is greater by between 50% and 200% than the thickness of the at least one microporous membrane layer facing toward the outer nonwoven layer.

8. The roofing underlay according to claim 1 , wherein the outer nonwoven layer has a grammage between 20 and 200 g/m 2 .

9. The roofing underlay according to claim 1 , wherein the inner nonwoven layer has a grammage between 1 and 150 g/m 2 .

10. The roofing underlay according to claim 1 , wherein the separating layer is a nonwoven layer, a perforated foam, an open-pore foam, a foam layer, a scrim, a textile, or an adhesive applied in a filamentous structure, a fibrous structure, and/or in a grid pattern, and the separating layer has a grammage between 1 and 150 g/m 2 .

11. The roofing underlay according to claim 1 , wherein the roofing underlay is selectively permeable or water-tight, with a water column between 0.8 and 40 m.

12. The roofing underlay according to claim 1 , wherein a water vapor diffusion-equivalent air layer thickness of the roofing underlay is between 0.02 and 0.5 m.

13. The roofing underlay according to claim 1 , wherein one or more of the at least one outer nonwoven layer, the at least one inner nonwoven layer and the separating layer includes a plastic material, a thermoplastic material, polyester (PES), polyethylene (PE), polypropylene (PP) and/or polyethylene terephthalate (PET).

14. The roofing underlay according to claim 1 , wherein adjacent membrane layers are joined to the inner or outer nonwoven layer by ultrasound welding, punctual spot welds, bonding, punctual partial bonding, and/or by hot calendering.

15. The roofing underlay according to claim 1 , wherein immediately adjacent membrane layers are joined together across separating layers by ultrasound welding, punctual spot welds, bonding, punctual partial bonding, and/or by hot calendering.

16. The roofing underlay according to claim 1 , wherein an adhesive area is provided on at least one edge at a bottom and/or at a top side of the roofing underlay.

17. The roofing underlay according to claim 1 , wherein the roofing underlay is a roof cladding underlay or a roof lining membrane.

18. A method for production of a roofing underlay having at least one outer nonwoven layer, at least one inner nonwoven layer and at least one microporous membrane layer based on a polyolefin plastic, wherein the membrane layer is arranged between the outer nonwoven layer and the inner nonwoven layer,

wherein

at least one further microporous membrane layer based on polyolefin plastic is provided between the outer nonwoven layer and the inner nonwoven layer and the at least one further membrane layer is separated from the membrane layer by a nonwoven separating layer, wherein the nonwoven separating layer is water-permeable.

19. The method according to claim 18 , wherein immediately adjacent membrane layers are joined together across separating layers by ultrasound welding, punctual partial spot welds, bonding, punctual partial bonding, and/or by hot calendering.

20. The method according to claim 18 , wherein an at least three-layer construction having the at least one outer nonwoven layer, the at least one microporous membrane layer and the nonwoven separating layer, is first produced by calendering and/or ultrasound welding, and an at least two-layer construction having the at least one inner nonwoven layer and the at least one further microporous membrane layer is produced in particular by ultrasound welding, and the at least two-layer construction is then joined to the at least three-layer construction by a punctual partial bonding and/or full-surface bonding, wherein the at least one further microporous membrane layer of the at least two-layer construction is facing the nonwoven separating layer of the at least three-layer construction.

21. The method according to claim 19 , wherein the ultrasound welding is performed using sonotrodes.