acceptable solution

DIAMOND CAVITY
Plaster System

Effective March 2003

This information is prepared for the purposes of Hitex maintaining its alternate solution status whilst the Government re-assesses the BIA’s role with acceptable solutions. It is intended EIFS will obtain its own Acceptable Solutions in due course.

Only Hitex Registered Applicators are permitted to install and applicate the Hitex Diamond Cavity Plaster System.  Two phases of installation, fixing and plastering require specific trade skills.  Fixers shall carry Hitex RA Fixer’s Certificate and Plasterers the Hitex RA Plasterers Certificate.  These shall be kept current. 

Warrant of fitness shall be issued by Hitex, the manufacturer, for each Hitex Diamond Cavity Plaster System.  This warrant of fitness can be completed once the Registered Applicator has issued the Hitex Works Compliance Certificate, a true record of compliance with Hitex Trade Practices.  The Warrant of Fitness can be re-issued following inspection if requested should either party of a sale process require an opinion on the state of the cladding.    

Warranty and Maintenance document shall be issued by Hitex, the manufacturer, for each Diamond Cavity Plaster System.  This becomes a true record of the 15 year durability warranty (B2) and 5 year workmanship. Maintenance requirements are clearly detailed to the homeowner in this document.  Hitex conduct an extensive manufacturing program. 

Manufacturers Materials only shall be used.  No substitution shall be allowed.  Hitex Trade Practices clearly define materials allowed.   All materials are clearly marked with Hitex Branding.

External Moisture.  Recent concerns in the building industry regarding entrapped moisture requires the cladding manufacturer to a design cladding system in such a way that any moisture build-up in the timber frame be able to dry out safely.  The unique Hitex Diamond Cavity System is the first monolithic cladding system in New Zealand with a proven drying performance once the leak has been stopped. 

See Hitex Research Bulletins 

Testing  Hitex has been subjected to Fire Tests, pull through wind zone tests and Weathertightness tests (BRANZ).  Thermal tests, Acoustic tests and Drying tests (Auckland University).  Permeability tests and Water Absorption tests (Stevenson’s).   Impact tests and Tensile tests (Opus, formally Works Consultancy).  These reports can be obtained on request. 

Design Criteria

The Hitex Diamond Cavity System (Patent pending) is unique in the way the polystyrene has been formed to prevent the building paper from sealing off the cavity.  Each Diamond sheet allows air to flow three dimensionally around the building without the need for battens.

Insulation.  To maintain the thermal value, the minimum thickness of the Diamond Cavity system is 50mm.  This provides an R value of 1.6

Flashings.  Sleeves shall be used for all penetrations including pipes, brackets and bolts.  Full flashings are required for window heads, deck edges and roof intersections of walls. 

See Hitex Trade Practice and Hitex Information Bulletins.

Wind Zones.  Hitex’s standard nailing system with plastic washers is acceptable in all New Zealand Wind Zones

Building Paper.  Current Hitex research projects clearly show wood drying rates are greatly reduced with the introduction of Building Papers.  Hitex is continuing this research and will advise the industry of the outcome.   Until then building papers allowing the greatest diffusion are to be specified.

Undersill Trays for Windows.  Recent publicity has been focusing on the failure of aluminium window mitres.  Whilst several ingenious products have surfaced the only one that works, in Hitex’s opinion, is a fully turned up metal sill tray.  No others can turn water out over the EIFS Sill Flashings or pass the Weather tightness test of wind driven moisture.

Drawings.  Standard drawings for detailing are available from Hitex.  It is envisaged that as regulations tighten the use of some products will be restricted or even banned.  Therefore drawing changes and ‘one-off’ detailing can be expected for the next year.  In the meantime Hitex has published Better Building Practices 2002 for your consideration.

Treatment of Timber.  It is envisaged that H1 plus will be mandatory shortly.  This will offer timber protection for a period of time to hopefully allow the leak to be identified, corrected and provide the timber time to dry out safely.  H1 plus boric treated timbers offer the greatest resistance to the formation of mould and fungi.

Mould and Fungi.  The treatment of timber does not mean gib board and other building elements will not mould if they either become wet or are trapped in a high humidity or wet section of the wall.  Care must be taken when specifying these building materials.

Fibreglass Batts.  It has been common practice for builders and homeowners to install batts in the walls in addition to EIFS polystyrene cladding on the outside.  Be advised that it is more beneficial to increase the thickness of the polystyrene to gain thermal efficiency and delete the batts.  Batts cut off the thermal movement of air in the wall and reduce the ability of moisture to aspire through the building paper meaning timber stays wet longer.  Wet batts grow mould.

Ventilated Cavity.  Hitex is currently conducting tests on the usefulness of air ventilation behind the Diamond Cavity Plaster system.  Hitex is testing a ventilation damper (patent pending), which can be retrofitted and has the ability to be shut off when not required.  This means no thermal loss when ventilation is not needed i.e., only opened for use if the timber is wet.

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Page last updated Tuesday, 08 March 2005