Naturally Aspiring And Diamond Cavity Systems

Building Industry Experience Shows

Building components are letting water into framing.  New buildings are leaking from day one.  Older buildings develop leaks as things age.  Blame is passed around.  Whilst the building may comply with E2 of the building code at certification, it does not comply shortly afterwards.  Home owners do not understand the need for repairs as soon as possible or adequate maintenance.  Untreated framing is more susceptible to rot than treated timber. 

For a building element to be of merchantable quality it must withstand “in service use” conditions as found in this country.  In other words any supplier promoting products for use in construction must supply them with the knowledge that the building will leak in its life time.  If they continue to supply, or change standards to gain the right to supply, then they must factor this warning into account.

A Plaster Cladding System’s primary function is to keep water out, but it must also be able to allow any intrusive water (and moisture) to have the ability to escape.

It is an acknowledged fact that untreated timber framing will rot (when subjected to wetness) far more extensively and quicker than H1 Boric or H3 Tan timber does.  If your building is being designed to use untreated timber the following warning is appropriate.

WARNING: Untreated timber homes require greater maintenance and if water enters unnoticed, and not dealt with immediately, extensive repair costs including replacement of studs will be necessary.

To assist designers to overcome the “unventilated framing” era of the 90’s, Hitex offers the following system solutions.

Naturally Aspiring Walls

Applications:

(a)  Isolated gable with drip edge

All framing is exposed to ventilation at the rear so timber can naturally dry
i.e. No gib board.

(b)  Upper roof areas or pop - tops

Baseplate is exposed to natural drying within the ceiling space.  This will not
stop sill plates rotting but will save the baseplate and flooring i.e. No gib board.

Naturally Aspiring Walls, through their design, will allow a natural supply
of air to circulate around any damp timber so it can dry out and prevent rot.

(c)  Brick baseline with plaster upper.

Baseplate has cavity created by brick installation.  Most water will run down to the baseplate and be able to dry.  Sill plates above the brick cavity are still in danger.

(d)    Garages without internal linings.

This will allow air to dry out any dampness for as long as they remain unlined. i.e. No gib board.

Naturally aspiring walls are those walls where the framing (in particular the baseplate, which is most susceptible to rotting) is exposed sufficiently to natural air, which will, through circulation, dry out  timber to a safe moisture content.  Leaks that continuously supply more water than can be dried out will damage framing, but this would be discovered during maintenance inspections.

Diamond Cavity System

Application:

For structures, apart from those classified as naturally aspiring, there is a high degree of performance demanded as these walls have a higher occurrence of water entry through wind driven rain, leaks, and soakage.

Cladding systems need to allow structural members the chance of drying out before deterioration sets in where water enters from any leak source.  See information bulletin 2001/17.

Advantages of Diamond Cavity

	allows for drainage of liquid water
	allows for air to circulate and dry out wet timber
	allows an equalising effect to minimise the differences of pressure from outside the cladding forcing rain through cracks and capillaries.
	utilises all known drying mechanisms
	no horizontal or vertical blocks preventing drainage or air flow.
	proven 3D drying ability

Diamond Cavity can be installed with, partially or without building paper.  Where no building paper is used, proven faster three dimensional drying reduces the risk of deterioration of framing and gib board and leaks are discovered earlier.  A disadvantage is that leaks will generally wet carpet but it acts as a good reminder to conduct repair work.  The more building paper used the slower the drying rate as moisture diffusion is greatly reduced with building paper.

Variable Hitex damper vents (patent pending) can be installed along walls to allow ventilation control within the Diamond Cavity meaning little effect on thermal values, even on exposed windy zones.  Moderate ventilation rates assist and speed up the drying process yet can be shut down and closed off once drying is complete.

Recommendation:

Currently the Building Industry in New Zealand is divided into camps.  Hitex believes that the above design consideration will assist designers to devise plaster cladding systems that will be of merchantable quality and assist water escaping before too much damage is done to the framing.  The building industry is not an ideal world where everything works as expected all the time.  The failure to accept the design suggestions above does not mean the cladding system will not do what the NZBC requires of it.  The acceptance of the design suggestions will reduce future costs of repair and lower the risk of unhealthy, rot infested buildings.

Page last updated Tuesday, 08 March 2005