Rain Penetration

Rain penetration and rain penetration control is a very important aspect of building science and building engineering. As the majority of low-rise residential buildings are constructed using traditional platform frame construction, moisture that penetrates the cladding to the interior wall cavity can cause significant damage to the performance, finishes and structure of a building. Rain penetration can prove detrimental to concrete and steel (especially light-gauge steel) structures as well.

The damage in the widely publicized British Columbia (the "Condo Crisis") and Wilmington, North Carolina problems can be linked to rain penetration combined with the long rainy season and short drying season of the warm coastal climate. The vast majority of the condos that were damaged were designed using a "face-sealed" wall system. The face-seal relies on the integrity of the outer surface of the cladding to prevent the entry of water into the wall system. Water that reaches the sheathing or enters the stud-space can initiate decay and corrosion of structural members. More wide-spread rain problems in North America due to rain penetration include damage to finishes, mold problems, and cladding deterioration.

Rain penetration occurs through a number of different mechanisms:

A rain control primer can be downloaded Click here. The publications section contains much more information on rain control, especially as presentations.