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Newton 420 Reservoir 0.92m x 50m

£549.50 Ex VAT
£659.40 Inc VAT

A large drainage and water retention membrane designed to deal with water on an extensive green roof.

Extensive Green Roof Drainage Membrane

Newton 420 Reservoir membrane functions as both a drainage and water-retention membrane. It provides a water reservoir to support extensive green roofs that feature sedum, herbaceous plants, mosses or grasses above decks and roofs.

When the reservoir membrane’s water-retaining cups are full, the large drainage holes allow water to easily pass through to the waterproofing layer below. This prevents saturation and any waterlogging of the soil in the green roof above.

The Newton 420 Reservoir also features a bonded geotextile layer that prevents soil from entering the storage cups during the backfill process. This guarantees both maximum reservoir storage and maintains drainage capabilities. 

Uses of Newton 420 Reservoir Membrane

Newton 420 functions as a water-holding and drainage layer above a deck, flat roof or pitched roof where shallow planting is used in an extensive green roof system.

Newton 420 Reservoir should be used in conjunction with a primary waterproofing membrane. It forms a key part of a waterproofing system for:

  • extensive green roofs
  • decks
  • flat roofs
  • terraces
  • balconies 

Installing Newton 420 Reservoir Membrane

Newton 420 membrane should always be used above a primary waterproofing membrane.

Start by rolling out the reservoir membrane in the direction of the fall. The geotextile surface should be facing upwards. Cut the membrane to length with a utility knife or shears.

Install any subsequent membranes adjacent to the previous length to form a simple butt joint. The extra flap of geotextile should overlap the joint.

Note: It is not necessary to overlap the dimpled cores.

Take the 420 Reservoir Membrane into the double entry drainage outlets. You don’t need to seal to these outlets or seal around any protrusions through the membrane.

Permagard - Providing Solutions. Inspiring Confidence.

If you have any questions about Newton Reservoir membranes or green roof systems in general then contact our technical team on 0117 982 3282.  

You can browse a wide range of Newton membranes and waterproofing products


  • Deals with large volumes of water
  • Large drainage holes for a much higher drainage flow
  • Tough and durable HDPE drainage membrane
  • Quick and easy to install
  • Integrated non-sagging geotextile layer to filter out soil particles
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