Here is the fifth part concerning facade inspection. We will deal with the question of metal fasteners for brick walls. These fasteners are therefore the elements connecting the brick facing to the structure of the building.
Role of metal fasteners
Let us mention that the fastening clips of the masonry transfer the lateral load of the wall, towards the structure of the building, and then prevent the movement of the lateral wall towards the outside. This can cause the brick wall to collapse.
The installation of metal fasteners is essential for the lateral stability of brick walls. It is essential that the installation respects the rules of the art and the Building Code in force. Thus, the fasteners must absolutely withstand lateral forces and corrosion.
In old buildings, at the beginning of the construction of the brick walls, they were fastened against the wooden planks with nails, which corroded over time and separated from the wooden planks. This caused bulges in the brick wall [colloquially known as beef belly].
Two types of movement
In general, there are two types of movement in brick walls attached to wooden planks. The first type of movement is the detachment of bricks from the structure of wooden planks in the upper part of the wall. This phenomenon is caused by the corrosion of the nails, at the top of the facing, by the exfiltration of moist air.
Indeed, the exterior walls of the log buildings of the time are poorly insulated. There is therefore significant heat loss through these walls in the upper part of the building. The reason is that warm, moist air rises to the upper ceiling of the building by the chimney effect. Thus, the moist, warm air - which passes through the wooden planks to the outside - attacks the nails in the cladding of the last rows of bricks at the top of the building. These nails deteriorate and separate from the wooden planks, and the bricks move outward to form an ox belly.
Sometimes, the presence of water infiltration behind the bricks causes the corrosion of the fastening nails. This situation also leads to detachments from the bricks of the plank walls.
As regards the second type of movement, one can also find detached and displaced brick walls at the base of the siding. This movement of the bricks is generally caused by the collapse of cemented stone foundations.
When bulging brick walls, remove bricks from affected areas and replace fastening nails with galvanized steel strips. It is best to use two-component metal fasteners. These fasteners must be fastened to the wooden structure with twisted nails or screws having a diameter in accordance with the current Construction Code.