Exterior cladding is an essential component of a building, both for aesthetics and for protection against the elements. In fact, cladding cannot be considered the building's envelope , but rather an element of that envelope, which comprises all the components of the building's outer shell. These components include the vapor barrier, insulation, wood framing, air barrier, roofing, foundation, and so on.
Sealing system
In general, the exterior covering is not completely waterproof and a certain quantity of water can, during rain, pass through the exterior covering towards the rear of it.
Water that infiltrates – towards the rear of the exterior covering – must not come into contact with the wooden structure. For this, there must be an air and weather barrier membrane that blocks the passage of water.
After that, the water circulates - towards the base of the exterior cladding - in the void between the exterior cladding and the air barrier membrane. Finally, the water must be directed to the outside of the envelope through the base flashing and the perforated moldings.
Exterior cladding installation deficiencies
There are three problems that can arise when installing exterior cladding, namely: 1) the base of the cladding being completely enclosed; 2) the seat rail which is poorly protected by the exterior covering and; 3) base flashing not properly installed.
Closed covering base
The installation of an exterior cladding must not prevent the drainage of water to the exterior. One of the most common problems encountered is when the base of the coating is completely closed. We have found this kind of problem with several types of coating (acrylic, wood, vinyl, aggregate, etc.).
In the case of cladding with horizontal siding , the furring strips must be installed vertically behind the cladding. This allows water to flow freely at the base of the exterior cladding. However, most of the time, pieces of furring strip are installed horizontally between the vertical furring strips and at the base of the siding.
If the installation of a horizontal furring strip is unavoidable, then there must be clearance between the pieces of the first furring strip at the bottom of the wall, to allow water to drain to the outside of the envelope. In addition, at the base of the exterior cladding, a perforated molding must be installed to evacuate water to the outside of the cladding.
Poorly protected seat rail
Another common problem is that the exterior sheathing doesn't adequately protect the sill plate . In fact, the sheathing should overlap the foundation wall by 1 inch to protect the sill plate. Furthermore, the air barrier membrane must be properly installed to ensure a tight seal over the sill plate to prevent water and air infiltration into the building.
Base flashing improperly installed
The third problem arises when the base flashing is not properly installed, specifically when it is not tucked behind the air barrier membrane. This allows water to penetrate – between the air barrier and the flashing – into the structure.
Poorly executed work during the installation of the exterior cladding causes water to seep into the building, particularly at the junction between the sill plate and the top of the foundation wall. This subsequently leads to rot in the wooden structure.
Improper installation of the air barrier membrane and cladding at the sill plate allows air to enter the interior ( air infiltration ). This then leads to condensation on the foundation walls and mold growth on the building materials.
© Moisture and degradation of the wooden structure can be observed under the acrylic coating.