Cladding Underlay

Australian Standard AS 4256.4 -2006 states the following: Type B cladding shall only be used when fully and continuously supported over structural framing or over existing walling. Classification: Type B cladding is defined as having a transverse bending stiffness less than 1.0 Nm2, in accordance with AS/NZS 4257.9.  All foam backed vinyl (PVC) cladding falls into this classification – Type B Cladding This means that for new construction or over new framework, foam backed vinyl cladding must be installed over an underlay to meet Australian Standards. It is also recommended that studwork be built with 450mm centres.

cladding underlay

Recommended underlay choices:

  • Levelwall foam wrap – available from Mitten Vinyl Australia
  • 4.5mm thick plywood sheeting – available from hardware/building suppliers or timber yard
  • 4.5mm thick fibre cement sheeting – available from hardware/building supplies

Levelwall Underlay

Levelwall acts as an insulation wrap, reducing air infiltration, insulating timber studs and reducing noise transmission. It also provides a smoothlevel surface over framework for the application of vinyl cladding, and ensures the cladding is fully and continuously supported, as required by Australian Standards. Read more about installation requirements at our Trade Desk.

Mitten Vinyl Cladding Underlay


  • Provides insulation plus reflective foil for increased R value
  • Rigid support for cladding to meet Australian Standards
  • Supplied in fan-fold packs of 24 panels covering 17.7 sq metres
  • Patented grid system on the panels for easy measuring and cutting
  • Manufactured from high quality expanded polystyrene
  • Rigid panels make cutting around doors and windows easy
  • Hinged fan fold design lays absolutely flat for cutting , and seals completely at the joints

Silverwrap Sarking

Tough Wall Wrap Reflective Insulation – use over underlay on new framework or over existing fibro for increased insulation and waterproofing.


  • UV Stabilised
  • 97% reflective
  • Fire retardant
  • Compliant to Australian Standard AS/NZS 4859.1

Available in rolls of 60 metres.

For more information on our cladding underlay, contact Mitten Vinyl Australia today on 1300 66 55 43.