Single Ply Membrane - Cut-to-Falls
Product
Polyfoam Cut-To-Falls is a specially designed system of pre-cut
tapered high performance, 100% ozone friendly, extruded
polystyrene, rigid board insulation. Typical board sizes are 1200 x
600 and cut to suit any fall scheme, though most are either 1:40 or
1:60.
The boards are straight edged and can be supplied with a foil
facing to suit pvc single ply membrane applications.
Typical Construction
Polyfoam Cut-To-Falls boards are suitable for use on all types
of roof deck which are constructed without a fall. The boards are
laid over a vapour control membrane and mechanically fixed or
bonded to the deck.
The insulation is overlaid with a single ply waterproof
membrane.
Installation
The vapour control layer should be laid over the structural deck
and all joints lapped and bonded. Polyfoam Cut-To- Falls boards are
supplied clearly marked with a laying scheme for their application.
Each component will be marked on the diagram and should be laid as
indicated starting at, and working away from, the drainage
outlet.
In a bonded membrane system each layer of the Cut-To-Falls scheme
must be bonded as well as the waterproof membrane itself.
When a mechanically fixed membrane is being used, the Polyfoam
Roofboards should be mechanically fixed to the deck with two
centrally placed fixings in each board to secure the boards in
place before the membrane is fixed.
Compression resistance
All materials are compressed under load. If the roof is going
to be transformed from a limited access waste of space into an
interesting and useful space the insulation must be capable of
accommodating applied loads. Polyfoam Cut-To- Falls schemes are
highly resistant to compression and withstand both occasional and
long term static loads.
Moisture
resistance
Polyfoam Cut-To-Falls schemes are resistant to moisture absorption
and can be laid in standing water or up against wet concrete with
minimal impact on the performance of the product.
Thermal insulation
Polyfoam Cut to Falls has a thermal conductivity of
0.029W/mK
The actual performance in use of Polyfoam Cut-To-Falls is outlined
in the below table.
Fire Performance
When Polyfoam Cut-To-Falls is installed in a roof construction
it will not contribute to the development stages of a fire. When
overlaid with a single ply membrane the performance of the finished
roof will depend on the membrane used. Please consult the membrane
supplier for more details.
Typical U-Values (W/m2K) of flat roofs insulated
with Polyfoam Cut-To-Falls
| Polyfoam Cut-to-Falls minimum
thickness (mm) |
19mm chipboard, timber joists and
12.5mm plasterboard |
Profiled metal deck |
150mm concrete, 40mm screed & 13mm
plaster |
| 140 |
0.19 |
0.20 |
0.19 |
| 130 |
0.20 |
0.22 |
0.21 |
| 110 |
0.23 |
0.25 |
0.24 |
Note: Single ply membrane finish
assumed.The U-Values have been calculated to BS EN ISO 6946: 1997
For project specific calculations contact our Technical Advisory
Centre on 01744 766666.
Advantages
- Suitable for terraces, balconies and other pedestrian
areas
- Supported by specialist design service with installation
advice
- Bespoke system designed to meet the needs of each individual
project Please contact Knauf Insulation for details.
- Easy modular component installation
Typical example of cut-to-falls plan
