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Blog by Buchamer Inspection Services Ltd.

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Exterior Siding Water Penetration Control

Rain Water Penetration Control

There are three different strategies for rain penetration control in walls: face seal,concealed barrier and rainscreen walls. Any type of cladding can be used with these three strategies. However, the performance expectations, as well as the maintenance and renewal requirements, will vary depending on the rain penetration control strategy.

Face seal wall assemblies rely on the elimination of holes through the cladding to limit water ingress. Discontinuities in the face seal (cracks and holes) can result in water entering the wall where it is unable to readily drain or dry. This in turn, can lead to premature deterioration of the cladding and the hidden components of the wall. Face seal walls are generally only appropriate when they are protected by significant overhanges and are rarely exposed to rain.

Concealed barrier walls also rely on the elimination of holes through a single layer, although in this case, the layer is protected or concealed behind the cladding. Typically, the sheathing membrane is the layer this is made continuous in order to control rain penetration. Since this layer is protected, it is more likely to provide adequate performance than a face sealed assembly.

Rainscreen walls are designed to take into consideration that some water will likely penetrate past the outer cladding surface and, therefore, two lines of defence are provided. The cladding provides the first line of defence while the sheating membrane provides a second line. An air space is provided between the cladding and the sheathing membrane on the back-up wall that facilitates drainage and drying. Rainscreen walls provide more reliable and durable performance due to the multiple lines of defence, or redundancy, in the design. Therefore, they are less dependent on maintenance to ensure adequate performance.