For Flat, Curved & Sloping Roofs

For Flat, Curved
& Sloping Roofs

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We've waterproofed 180m SqM of roofs!

We've waterproofed
180m SqM of roofs!

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alwitra Rainwater Outlet Horizontal
alwitra Rainwater Outlet Horizontal

Horizontal, rigid polyurethane body with EVALON® flange, 125mm, complete with screw ring and flat grating

  • Made of highly impact-resistant polypropylene (PP) 
  • On classic warm roofs, all standard vapour barriers can be flashed directly.
  • Corresponding extension pieces are available in various lengths, depending on the thermal insulation thickness

alwitra® Rainwater Outlet Horizontal

The thermally insulated alwitra® rainwater outlet W (horizontal) ensures reliable connection between the waterproofing at cold or inverted roofs and horizontally installed drainage pipes.


  • W 125 for connecting to drainage pipes with socket DN 125 (OD 125 mm)
  • W 75/110 with small overall height for connecting to drainage pipes with socket DN 70 (OD 75 mm) and - with included eccentric adapter 75/110 - to pipes DN 100 (OD 110 mm)
  • A combined leaf guard / gravel stop is included.


  • Cold and Warm Roofs

Product Details Back to top

Technical Drawings

alwitra Rainwater Outlet Horizontal

Technical Data

Class (leaf guard / gravel stop): H 1.5
Discharge: Horizontal
Material: Highly impact resistant PP
Colour: Black (optional connecting
flange in the colour of the waterproofing membrane)
Required roof opening: W 125 190 x 280 mm
W 75/110 190 x 250 mm
Min. Installation height: W 125 approx. 200 mm
W 75/110 approx. 110 mm
Outer diameter flange: 290 mm
Number of screw holes in flange: 3
Ø of screw holes in flange: 240 mm
Flange width: Approx. 50 mm
Connection diameter: W 125 125 mm (DN 125)
W 75/110 75 mm (DN 70)
110 mm (DN 100) with
included adapter 75/110
Outer diameter of optional connecting flange: 480 mm

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Our membranes are used by architects, contractors & developers. View all

Archdiocese of Liverpool
Coventry City Council
3D Reid
Balfour Beatty
InFrame Garden Rooms
Fife Council
Angell Thompson
Alec French Architects
Aloft Roofing & Leadwork
English Heritage
Glasgow Housing Association
Coomber Associates
Ashtree Roofing

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Here's what some of our clients have to say...

We have been alwitra® contractors for many years and have always been impressed with the results and reliability of the product. The customers…

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I, James Hopkins Director of JH Specialist Roofing install single-ply membranes on a daily basis, we as a company have tried numerous types of…

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We have used VSK extensively over the last 5 years, we have found it to be a great product and really good for complex detail work. We find using…

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As a small flat roofing business carrying out mostly domestic refurb work and small extensions EVALON® VSK is our preferred single ply membrane…

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We have been an approved contractor for many years, the level of customer service and the quality of the products provided by ICB (Waterproofing) is…

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We have worked with ICB on several occasions and we would thoroughly recommend them for their high level of professionalism and efficiency. The team…

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OB Architecture

ICB provides an excellent service with all the professional back-up required at the development stage through to completion. The manner in which you…

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I am pleased to recommend ICB as Company, through my personal experience and that of my Business, for the following reasons: They are an easy Company…

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We believe, as one of your approved contractors, over the years we have had a great working relationship with yourselves. When working on projects…

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Best system on the market – VSK all the way!!!!!!


alwitra® is a lovely membrane when you have some detailing and gutters as you can go all the way through in a oner…


…that’s the beauty of this membrane, (you) can complete field sheet and upstand in one go, nice and tight and (a) crisp finish in the…

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This product has to be the most versatile single-ply system we have used. Unbeatable finish.

Lee Orchard

EVALON® VSK – such a quality and versatile membrane.

Lee Orchard

In my mind the best single-ply.


Can’t beat VSK


We find all the staff at ICB, friendly, helpful & knowledgeable.


EVALON® VSK! Surely the best single-ply waterproofing membrane ever produced! A++++


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