The sill plate plays an important role in the structure of a building, because this element forms the link between the wooden structure and the foundation walls. In other words, the rail attaches the wooden structure to the foundation walls. By definition, it is a piece of framing anchored to the level (the top) of the foundations and on which the floor joists rest.
Installation required
The position of the seat rail on the foundation wall depends on the type of coating video shooting. In the case of a masonry cladding, the rail is installed towards the inside of the foundation walls, to leave a space which will allow the masonry to rest on the foundation walls.
In the case of a light covering, such as acrylic, vinyl or wood (or others), then the rail is installed towards the outside of the foundation walls.
The sill plate must rest on the foundation walls and be anchored to these walls. A sealing material must be installed between the concrete and the wooden rail, to prevent air infiltration towards the basement, and block the movement of humidity towards the wooden structure.
Causes of rotting
The sill plate is the most vulnerable element which runs a great risk of rotting from moisture and water infiltration in the building. This is because this element is located in a strategic location, namely between several building systems: the foundation walls, the wooden structure and the exterior envelope.
Several years of experience in hidden defect cases have allowed us to establish the main causes which directly contribute to the premature rotting of the seat rail:
- The first cause of rotting, in the case of an exterior facing in masonry, is explained by the fact that at the base of the facing, there is a waterproofing flashing – installed on the foundation wall – which is at the same level as the sill plate. This flashing extends behind the air barrier membrane or the black paper.
In the event that there is a waterproofing problem in this system, then the water seeps inward into the basement. The first element that can be affected by water is the foundation rail which is installed horizontally on the foundation walls. It is even more problematic if there is an absence of chantepleures at the base of the masonry, which was common in buildings constructed before the sixties, because the concept of chantepleures was not known.
- The second cause of rotting occurs in the case of a facing video shooting closed, such as an acrylic covering closed at the base (i.e. there is no water drainage system to the outside). Thus, water which can infiltrate towards the rear of the coating (through cracks, because of missing or poor sealing joints, etc.) remains trapped behind the acrylic coating, particularly at the base. of the facing. The seat rail, when there is a acrylic coating, can be completely decomposed due to excessive humidity – which has persisted for a long time – or water infiltration behind the coating. In fact, the water remains trapped at the base of the facing on the sill plate.
- The third cause of rotting relates to the intermediate covering which does not cover the sill plate. In several buildings, the sill plate was covered with plaster. So, the smooth is totally rotten by the moisture absorbed by the roughcast.
As soon as the sill plate becomes damp, it creates a suitable place for the activities of carpenter ants who find an ideal path to go outside or inside the building. The most common place where there is rot in the sill rail is under patio doors. Also, there is a possibility of discovering a rotten seat rail when the terraces and the balconies are installed higher than the foundation walls.
Rotten seat smooth
