Stucco embedded into ground needs drying skirt

Stucco and Harditex are absorbent claddings which wick dampness from the ground.

Without a cavity this wets the framing and causes decay.

Walls with plaster (and any absorbent cladding) that are embedded need changing. First these walls must be invasively tested to establish if the framing is already decayed, or capable of being treated with RotStop and fitted with a drying skirt.

Monitoring will determine the improvement in moisture content readings.

The cladding is cut up to the level of the concrete floor so the drying skirt can be fitted. This stops wicking. The drying skirts have a unique cavity 'slot' fitted allowing wet framing to release vapour and dry.

Of interest is once the drying skirt is installed, future monitoring will identify any areas with active leaks that need fixing.


 

Absorbent claddings must have ventilation.

The 1953 standards required adequate ventilation. Adequate means sufficient air circulation to keep framing dry should it get wet.

I found this report by BRANZ presented to 'Building and Environment' in Great Britain in 1983. In summary BRANZ were studying why walls in homes had become damp and moldy since the mandatory insulation legislation in 1978. Government wanted warmer homes so made insulation compulsory. The unintended consequence was the wall insulation blocked off air circulation of drill holes and some cavities. Walls made with absorbent claddings did not dry out and became moldy. But they had well treated timber so at least decay was temporarily held back. BRANZ summary was:

• Cannot under any circumstances enclose framing
• Winter wet up periods were longer than summer drying so some walls got wetter naturally
• Construction moisture could take up to 4.6 years to dry
• The framing at this time was treated to C8 or 0.8%BAE so controlled decay 

Why didn’t BRANZ and BIA follow this up and require cavities? I believe this paper was released overseas and not in New Zealand because if homeowners of homes built after compulsory insulation were told they would have massive claims to reclad with a cavity.
What we know from this research is defects at construction will leak, products age and fail and leak, walls get condensation and subject to vapour diffusion. The only way this can be managed is with air circulation ie cavity, and breathing. This makes all Harditex and Stucco claddings defective and not fit for purpose as they have enclosed the framing.
Now you are out of time to claim but at least you can find out how badly affected your home is with invasive testing and whether the option of drying skirts will help.

 

New Zealand Standards required 'adequate ventilation'

MP 3640:1992 (and its predecessors back to 1953) required framing to be 'adequately ventilated'.

Clause 9.1 of the Standard relates to H1 framing. It must have adequate ventilation. But even more concerning is H1 is not approved for external walls. H1 must be protected by external walls.

Where absorbent claddings do not have H3 framing with a cavity they will need recladding, or if the invasive testing shows they are not badly damaged they may be able to be corrected and made durable by treating the framing with RotStop and fitting a drying skirt. This way the framing can be made durable for external walls and can dry out via the ventilation of the drying skirts. This overcomes the moisture transport mechanisms (except active leaks which must be fixed).