NBS Source
Newton 420 Reservoir


Suitable for use as a water holding and drainage layer above a deck, flat roof or pitched roof where shallow planting is used to create an extensive green roof.


A unique drainage and water-retention membrane for use where a water reservoir is required for extensive green roofs of sedum, herbaceous plants, mosses or grass above decks and roofs.

Unlike other products of this type, Newton 420 Reservoir has a bonded geotextile that prevents intrusion of the soil into the water holding cups during back-fill and compression. This results in a permanently larger volume reservoir than any other 20 mm deep green roof membrane.

When the water holding cups are full, the large drainage holes within the high-density polyethylene (HDPE) core allow water to easily pass through to the drainage layer below to prevent saturation and water logging of the green roof above.

Newton 420 Reservoir should continue over construction and movement joints and acts as a decoupling membrane preventing movement from the substrate transferring through to the surface finish.

Consult manufacturer's literature for relevant surface preparation.

Features and benefits:

  • Unique bonded geotextile does not sag into the water holding cups as is the case with loose laid geotextiles.
  • Large drainage holes allow a much higher drainage flow through the membrane than comparative products, ensuring that when the water holding cups are full, the water drains quickly so as not to waterlog the soil.
  • Suspended soil particles (fines) are filtered out by the geotextile layer.
  • Large drainage layer created by the 20 mm HDPE core.
  • Tough and durable.
  • Quick and easy to install.

General information


Studded core: Black, Geotextile: White


Wrapped label rolls which weigh 70 kg


21 x 920 x 50000 mm

Uniclass 2015

Pr_25_57_65_60 Plastics sheetsPrimary


J40/295 Geocomposite studded cavity drainage/ venting membrane

Q37/130 Extensive green roof

Q37/350 Drainage layer

Product range

External Waterproofing and Drainage Membranes

Specification data - Plastics sheets Enhanced data


Studded core: High density polyethylene (HDPE), Geotextile: Polypropylene.


To EN ISO 12958, BS EN 1931, EN ISO 12236, EN ISO 10319 and to EN14030/ EN ISO 13438.

Physical properties



Studded core: Black, Geotextile: White.

Weight (minimum)

70.00 kg.



Thickness (minimum)

1.2 mm.

Product Reference

Newton 420 Reservoir (M31)

Studded layer

High density polyethylene (HDPE).

Filter layer


Stud depth

19 mm.

Membrane height

20 mm.

Flow rate

0.07 L/m/s (at 20 kPa), 0.04 L/m/s (at 100 kPa), 0.02 L/m/s (at 200 kPa).

Water-flow at 20 kPa – 1:80 slope – Upper layer

0.07 L/m/s.

Water-flow at 100 kPa – 1:80 slope – Upper layer

0.04 L/m/s.

Water-flow at 200 kPa – 1:80 slope – Upper layer

0.02 L/m/s.

Compressive strength – Temporary loading

>240 kPa.

Compressive strength – Permanent loading

>120 kPa.

Water vapour diffusion resistance – Sd value

>604 m.

Water vapour diffusion resistance – µ value

>1 208 000 µ.

Water vapour diffusion resistance

>3020 MNs/g.

CBR puncture resistance

2800.00 N.

Tensile strength (Machine direction)

19 kN/m².

Tensile strength (Cross direction)

10 kN/m².

Chemical resistance


Oxidation resistance


Digital objects

Platform Compatible Version Certified to




Revit 2016


Download now from NBS National BIM Library


Newton 420 Reservoir Green Roof Drainage Membrane

Newton 420 Reservoir Green Roof Drainage Membrane

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