SR322 Weather grooves in weatherboard claddings (2015)
Product Description
Capillary grooves (more commonly referred to as weather grooves) have been formed into the lap joints in timber weatherboards in New Zealand from the late 1970s to this day. They are rarely seen in fibre-cement and wood fibre composite claddings. This study set out to measure the improvement in weathertight performance that could be attributed to weather grooves in timber claddings.
Within the margins of experimental uncertainty, no significant performance gains were seen in large-scale timber-clad walls that could be attributed to weather grooves. Other leakage paths around fixings and through natural knots and defects in weatherboards dominated leakage through the lap joints.
More tightly controlled measurements in small lengths of joint found some performance improvements in tight-fitting joints due to weather grooves. Higher peak wind pressures in fluctuating wind conditions were required to cause leakage than was the case in joints without a weather groove. These performance gains were seen at wind pressures beyond the normal working range of domestic claddings.
The passage of water through these joints was modelled to resolve the relative importance of surface tension effects and the reservoir capacity within the weather groove. A differential equation representing the equation of motion for water in the joint was solved to show that a weather groove can improve the weathertightness of lap joints in weatherboards. However, as demonstrated experimentally, this is only where the more common leakage paths have been eliminated. The theoretical advantages of the weather groove derived from the storage capacity reducing the leakage rate in fluctuating wind conditions.
Product Information
Publication date | 2015 |
---|---|
Author | Mark Bassett and Greg Overton |
System number | SR322 |