International Best Practice – Separating the wet and dry zones in the building envelope


Company: ARIDON

Uncontrolled rain water penetration remains the most fundamental threat to the structural integrity and performance of the building enclosure. The essential 4D’s of weather protection (Deflection, Drainage, Drying and Durability) need to be considered when specifying the building envelope. Claddings do the job of deflection but how good are the layers in behind the cladding at dealing with the other 3 D’s?

The Claddings Institute of New Zealand undertook a study tour in 2000 to the USA and Canada and identified the key findings:

  •  All buildings leak – More rain means more rain control is needed.
  • Moisture penetration is deceptive in its apparent simplicity.
  • The building envelope must have drying potential.
  • Greater building complexity leads to lower building performance.
  • The envelope is a climate transition zone that can provide ideal micro-ecological niches for destructive organisms.
  • The creation of energy efficient buildings has resulted in tight, cold and unforgiving claddings.
  • Scientific research is needed to better understand the building envelope and its role with moisture – Such understanding will eventually lead to a rational approach for the development and design of exterior wall systems.

International best practice has identified that wall constructions should be separated into the “wet zone” and the “dry zone” within the envelope. The wet zone is intended to be exposed to short and long term effects of rain water penetration and/or moisture ingress.

Think of the wet zone as two layers of defense – the cladding is like an umbrella and it blocks the majority of rain – however sometimes driving rain can get past your umbrella. This is where we need a strong second line of waterproof defense that can not only block the rain and ensure it is drained away from the frame (the dry zone) but also block the wind – as wind can drive moisture into the dry zone.

Finally a supplier has developed an exterior insulated weather-proofing wall system which suits any cladding type and provides superior protection for the frame against rain, condensation, wind and snow.



Figure 1: ARIDON® SMART WALL – Interlocking Panels:

Moulded interlocking joint with capillary groove and compressible V rib air & moisture seals. 




Rain is deflected down the panel and out the base. Compressible ‘V-Rib’ air and moisture seals prevent moisture moving into the framing cavity.


The ARIDON® SMART WALL comprises rigid interlocking panels which form a continuous weather resistant shell around the building wall frame before the claddings are installed. There is no reliance on thin skins, tapes or sealants for water proofing. The SMART WALL system includes all the flashings required to provide peace of mind from external moisture problems no matter how complex the building is.

The ARIDON® SMART WALL is the solution the NZ building industry has been looking for.




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