Floratec FS50 is a lightweight drainage and water storage board, manufactured from partially recycled, CFC free, expanded polystyrene, used mostly in extensive green roof applications. The product allows aeration of the substrate; evaporation of stored water and multidirectional drainage on the underside. Can also be used upside down on sloping roofs up to 15°.


Install by loose laying directly onto the root resistant membrane (overlaid with a moisture resistant mat on sloped roofs only). The 30 mm diameter water storage holes must be uppermost (except when installing on slopes, when the 55 x 55 mm box sections must be uppermost). Butt joint the boards together. Panels can be cut with a heavy duty knife or a small toothed saw to fit around protrusions. Overlay with an appropriate filter sheet and substrate. On sloped roofs, use filter sheet at perimeters and around protrusions only.

Standard product features




50 mm.

Panel size:

1 x1 m.

Dry weight:

0.7 kg/m².

Wet weight:

2.7 kg/m².

Water storage capacity:

2 litres/m².

Compressive strength:

10 kN/m².

Waterflow rate:

  • At 1:33 fall: 0.93 litres/second/m².
  • At 1:20 fall: 1.33 litres/second/m².

NBS Specification

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Product specification

An important note about specifying



Alumasc Building Products Ltd


+44 (0)1744 648400

Product reference

Floratec FS50

Manufacturer details

White House Works,
Bold Road,
St Helens,
Merseyside, WA9 4JG
Tel +44 (0)1744 648400
Fax +44 (0)1744 648401
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