Here is the fourth part concerning the inspection of the facades. In this article, we will demonstrate that the presence of rows of struts in the exterior walls of a building does not necessarily mean that it is a solid brick wall. It is true that in general, the solid wall is a supporting wall, but it is not always the case.
In fact, it is important to determine whether or not it is a load-bearing wall in order to propose a suitable and safe solution during repair work.
Massive walls and headers
The massive brick wall was used from the 17th century to the end of the 19th century in Quebec. It should be noted from the outset that the massive brick load-bearing walls are composed of several rows of bricks that form an integral structural body thanks to the struts. By definition, these are rows of bricks installed in the opposite direction of others to create proper fasteners between rows of bricks. This is to ensure that the load-bearing wall can withstand the loads of floors and snow and react as a solid structural body.
Reinforced concrete structure
During the invention of modern concrete, the builders used the reinforced concrete structure to replace massive load-bearing brick walls. In Montreal, at the beginning of the 20th century (1905 to 1922), reinforced concrete was introduced as a construction material in several industrial buildings. In this type of building, the bricks were used as an external wall to cover the concrete structural support elements. For example, concrete blocks or terracotta blocks were used to separate the interior from the exterior of the building. Therefore, the struts were used to fix the exterior brick wall against the structure without leaving space between the brick wall and the structure.
Counter Wall Theory
In the middle of the twentieth century, the theory of the brick wall against - which surrounds the structure (concrete, steel or wood) - was developed. It was to leave an air space (air gap) between the brick wall and the interior component of the structure, and to install a membrane on the structure to prevent water from entering the wall carrier. At the beginning of this practice, the chantepleures were not known, but later to ventilate and evacuate this space, we created chantepleures at the base of the siding and above the openings.
Brick wall and metal fasteners
To create a counter-wall (non-bearing), you need metal fasteners to fix the bricks against the plank structure. At first, these metal fasteners were simply nails fixed against the structure. However, there are buildings, 60 years, where we find a mix of both ways (old and modern), that is to say that we left a space between the brick wall and the concrete structure, but we used buttocks as fasteners. In these same buildings, there are no steel angles on the floors, to support the bricks in height, because the rows of struts transfer the load of the brick outer wall to the supporting structure (behind the bricks).
The addition of steel angleson each floor, as well as lintels above the openings was made necessary to support the bricks in the counter-wall system.
The massive brick load-bearing walls present problems different from those found with the current screen (against brick wall). Over time, water infiltration into the envelope eventually deteriorates the bricks. Sometimes the deterioration is so severe that the wall can not be repaired and needs to be replaced by the more modern brick wall system and load-bearing interior structure.
Deficiencies of modern buildings
Today, modern buildings have deficiencies that differ from those found in massive walls. These deficiencies are related to lack of maintenance or wear due to time:
- Chantepleures absent or blocked : We call “chantepleures” the water drainage holes placed at the base of masonry walls and above openings as well as at structural steel angles. They are needed to ventilate and drain the air space between the masonry and the building frame. There must be weepers at every 2 to 3 masonry units (hollow masonry joint).
- Efflorescence on bricks : Efflorescence is a white powder that can be found on bricks. The presence of this indicates that there are problems of water infiltration behind the screen. Thus, rainwater penetrates the outer casing through cracked or missing seal joints or by deficient, gap or missing flashings. The bricks absorb a good part of this water - having infiltrated behind the bricks - by rejecting moisture to the outside. The outgoing moisture carries mineral salts to the outside and deposits them on the surface of the bricks. This white deposit therefore reveals a problem of tightness in the building envelope. It is then necessary to check and repair the leaky points.
- Cracked or missing joints (around the devices piercing the facades): cracked, poor quality or absent caulking are major sources of water infiltration into the structure. For this reason, it is essential to inspect the joints regularly. These seals are found around openings (doors and windows) and devices that pierce the envelope and at the junctions of flashings and balconies, etc.
- Corrosion of lintels and steel angles : Corrosion of lintels or steel angles affects the capacity and structural integrity of steel lintels or angles. This situation greatly affects the integrity of the brick wall. Indeed, the corrosion of these important elements can cause cracks and shears in the bricks. In addition, the residues of the corroded metal can cause cracking in the mortar joints near the lintels and angles. Always carry out maintenance work on the lintels and angles to avoid these cracks.
- Shears and cracks in bricks Shears can be caused by many factors such as corrosion, as mentioned, as well as structural movement in foundation walls. Lack of expansion joints in the masonry structure can cause cracking. Another known deficiency is the bulging in bricks commonly called a beef belly. This phenomenon occurs when the metal fasteners are detached from the structure. Then the bricks move outward creating a mechanical detachment (beef belly). In older buildings that are poorly insulated, this phenomenon is found in the last rows of bricks at the top of the siding. The presence of ox bellies should not be taken lightly, as loose bricks may fall to the ground.
- Cracked vertical mortar joints : the mortar in vertical joints cracks with time, which can cause water seepage between walls. Subsequently, there is a deterioration of the components of the envelope. Therefore, the mortar must be removed from the vertical joints and filled with flexible sealing materials that rest on foam flanges (expansion joints).
- Hollow mortar joints : Over time and weather, mortar joints can crumble and fade. This situation weakens the masonry structure and allows water to penetrate into the structure, further deteriorating the siding. Repointing work is necessary if the problem arises.
Articles “facade inspection”