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Midspan Supports

Unless the thickness of the plastic sheeting is increased to equal the performance of the metal sheeting, mid-span supports or span breakers with a minimum thickness of 0.95 mm coated steel must be used as a mid-span support for all purlin spacings over 1.2 m.
Mid-span supports must not be used for more than one plastic sheet next to each other. Where two or more adjacent sheets are used together, the purlin spacings must be reduced to the maximum allowable for the profile, the thickness of the sheet and the design load.

A mid-span support is used at mid-span at spacings, dependent on the profile, to gain additional support from the metal cladding for the plastic sheeting.

Single sheets of plastic roof sheeting placed between adjacent metal sheets can only have the same purlin spacings as the metal roofing profile when a mid-span support is used, or the plastic sheeting thickness has been increased to provide the same performance characteristics as the metal sheeting. The exception to this condition applies only when the plastic sheeting has been tested for point loads as described in Wind and Point Load Testing.

The mid-span support member is not intended to support point loads from foot traffic and should be of sufficient strength and stiffness to prevent the plastic sheet deflection being greater than that of the adjacent metal sheeting.

Mid-span supports provide the uplift strength required to reduce sheet flutter in high winds. To prevent any movement between adjacent sheets they should be fixed with a type 17 screw and load spreading washer through the GRP and span breaker, and they should be fixed to the metal sheeting.

GRP with Mid-Span Supports

Plastic roof light sheets over metal.

 

 

 

Clause: 
014_008_004_000_000_000_000_000_000
Clause Number: 
14.8.4
/cop/installation/translucent-sheeting#midspan-supports
Revision Category: 
0 - Clause Removed
Revision Detail: 

Clause removed

Draft Clause: 
013_008_004_000_000_000_000_000_000