Here is the third part about the ifacades, masonry, bricks, steel lintels, mortar joints, chantepleures, cracks, shears.. At first, we drew up a summary the nature of such an inspection (Façade Inspection). Secondly, we have described, concisely, disabilities likely to be picked up by an engineer during a facade inspection. We now want to share with you some thoughts about the brick walls of some old buildings.
Non-bearing wall made of masonry
The techniques used to fix massive brick walls against the structures of older buildings are varied and depend on the period and prevailing building techniques of the time.
It is sometimes difficult to identify the facade system when the exterior walls are covered with bricks and stringers. This system may suggest that the exterior walls are massive load-bearing walls, because the presence of header generally means that the system is composed of load-bearing walls.
In Montreal, there are many buildings built before 1940, which were originally commercial or industrial buildings, with three (3) floors and more. These buildings have a concrete frame structure and not a structural system with load-bearing walls as it may seem from the outside. This is called BMR, a reinforced concrete framework with unreinforced masonry fill walls (MNA). See the diagram below National Research Council Canada.
Unreinforced masonry (unreinforced masonry) walls are usually made up of several brick walls. Headers are visible on the exterior surface. By definition, headers are bricks laid lengthwise. Therefore, one can discover the presence of the header rows by the ends of the exposed bricks normally at every sixth row of bricks (see photo). In fact, the header ties the partitions of the bricks together. However, care must be taken, as sometimes the infill walls made of MNA (unreinforced masonry) do not have headers and the outer walls of the bricks are held together only by mortar and metal ties. Commonly, we observe that the infill walls in MNA (unreinforced masonry) appear aged and show signs of wear and decrepitude.
Before starting the inspection of facades for this type of building, it is necessary to check inside whether or not there is a concrete frame which is normally visible and composed of massive elements (beams and columns in concrete). This reinforced framework is load-bearing and there are massive masonry walls on the outside. These walls are non-loadbearing, of the infill type in MNA (unreinforced masonry) and they are covered with a layer of exterior brick. This layer is connected to the interior masonry using headers or with metal ties against the concrete frame.
Interior masonry - which fills the sections bounded by concrete framing - may consist of two (2) 4 brick walls in thickness for each wall or a wall of 8 terracotta blocks. thickness. The concrete frame consists of columns and slabs of reinforced concrete that support the masonry filling the facades of the building.
Generally, the outer wall of this type of building shows signs of aging like cracks on the bricks themselves, hollowed mortar joints, broken and damaged bricks, bulges which are a sign of weakness of the assembly of masonry and degradation of metal fasteners. In most cases, the exterior brick wall is detached from the entire concrete frame and the walls of the interior masonry.
To repair the facades of this type of building, it is necessary to remove and remake the first brick wall at all places where there are bulges in the masonry walls. Metal fasteners and / or fascia should be examined at these locations and the bricks should be properly bonded to the concrete framing and interior masonry wall, if necessary.
If the bricks of the exterior wall are burst and / or damaged, the altered masonry units must be replaced with materials and methods similar to the original elements in order to maintain the original character. Total replacement of the exterior brick wall is preferable because usually the bricks are quite old, but it is optional. If the exterior surface of the brick is eroded, then the brick must be turned over to expose the other side.
Subsequently, it will repair the mortar joints. To do this, you must hollow out the joints to be repaired to a depth of 2,5 cm (1 in.), Clean the surface and water the wall. Then, the new mortar must be applied in layers by pressing well to compact it. At the last layer of mortar, you will need to shape the joint to match the entire wall. The other step is to repair the brick and mortar with products with colors, textures, dimensions and profiles similar to the existing one.
We want to warn about the potential difficulty of visually determining the type of exterior walls to be analyzed (either carriers or non-carriers). Therefore, to know exactly what type of exterior walls is being studied, an expert (engineer or architect) must complete exploratory holes as well as a thorough analysis before proceeding with repairs or modifications, etc. This is because a modification or repair in the exterior walls, without knowing the nature of these, can threaten the public safety or incur exorbitant costs for the owner.
Articles “facade inspection”
- Mandatory periodic inspection of facades and multi-storey parking lots
- Alert to degraded facades!
- Counter brick wall
- Unreinforced masonry
- Brick wall fasteners