HYDRA Classic Wall Underlay

HYDRA Classic Wall underlay is a premium fl exible synthetic underlay designed to be used behind exterior cladding systems.

It acts as a secondary weather-resistant barrier, protecting the building envelope from water ingress while allowing the safe passage of water vapour, contributing to a dry and durable wall assembly.

Scope

HYDRA Classic if designed, installed & maintained will meet or contribute to meeting the following provisions of the NZBC:

• Can be used with absorbent and non-absorbent claddings.
  
• Can be used with direct fix cladding and cavity applications.
  
• With masonry veneer in accordance with NZBC Acceptable Solutions E2/AS1 and E2/AS4.
  
• Can be used in all wind zones up to and including extra high when used with Rigid Air Barrier systems. Can be used installed as an air barrier in unlined spaces, such as attic spaces.

Limitations

• Must not be exposed to UV for greater than 60 days
  
• Insulation and internal linings cannot be installed until the exterior is completed.

Installation Instructions

1. Install with the printed side facing outwards.
   
2. Run the wall underlay horizontally from the upper side of the top plate to the underside of the bearers or bottom plate. Horizontal laps must be no less than 75mm with the direction of the lap ensuring that water is shed to the outside. Vertical laps must be over studs and a minimum of 150mm.
   
3. Ensure the wall underlay is taut and pulled tight over the framing. Fix with 6-8mm staples, 20mm large head galvanized clouts or proprietary underlay fixings. Fixings are required at 300mm centres vertically and horizontally.
   
4. For steel frame ensure the frame is free from dirt, oil and dust. Fix securely in place using galvanized pan head screws or double-sided tape. Note double sided tape is only a temporary fix until the cladding or battens are installed.
   
5. Run the underlay over all joinery openings, these should remain covered until the joinery units are ready to be installed.
   
6. Where stud spacing is greater than 450mm centres the wall underlay isnt permitted to bulge into the drained cavity, strapping is required to provide support.
   
7. Any damaged areas can be repaired with Marshall Construction tape or SUPER-STICK. Larger areas may require additional underlay and taping.
   
8. To form the openings for joinery units, the underlay is cut at a 45° angle into the centre from each corner. Return the underlay to the inside of the frame and fix to the inside of the framed opening. Trim off any excess underlay.
   • Use either SUPER-STICK Building Tape or MAXI-Butyl Flashing Tape for sealing around jionery openings, refer to the relevant installation guides.

9. It is recommended that HYDRA Classic Wall underlay is installed by or under the direct supervision of a licensed building practitioner.
   

Storage

Store in a clean and dry area out of direct sunlight. Keep the rolls
off the ground and don’t store anything heavy on top of rolls

• Hydra Wall Installation Guide (1 mb)