How was the external side wall which supported the roof constructed?
It is important to understand the way the side wall supporting wall that collapsed inn September 2023 was constructed. In this way we can better understand the level of strength and over engineering that was applied to the structure to make it impervious to any type of stress exerted by the roof at any time even during a possible roof failure itself. In other words, the original design and construction of the side wall was as such that it would have withstood any type of stress, including the lateral stress imposed by the roof.
Understanding the original construction of this supporting structure is essential because it was the collapse of this wall that caused the cascading collapses, the first being the roof in September 2023 that it supported and the second slow collapse of the adjacent roof (late October beginning of November 2023) a couple of months after the first collapse of the side supporting wall in September 2023.
The original construction design in order to ensure sufficient strength of the side wall required the implementation of reinforcing internal pillars embedded in the double brick wall construction. It is important also to realise that the wall was further reinforced by the fact that all entrances and windows had all long ago been bricked up. The bricking up of any openings of wall caused the structure to be reinforced even further. Making this supporting wall even stronger than the original design and construction.
Therefore this wall was of solid double brick construction with internal reinforcing pillars and all openings were carefully bricked up. As it is evident from the existing side wall, the embedded pillars have the function to reinforce the structure, making it impervious to static side forces imposed by the weight of the roof. In essence, the roof structure can fail but none of side the walls will collapse as a result of the collapse of part or all of the roof. As further proof of this, despite the natural collapse of the second roof (Late October and beginning of November) this is not causing any strain on the side wall which will or may cause it to collapse even partially at any point in the future. This type of construction is standard for building of this age and it make them really durable solid structures which are not expected to collapse due to deterioration of roof joist rot or any roof structural defect. In essence, this type of construction makes the side wall impervious from either partial or total collapse due to any stress imposed by the roof above.
Lateral forces imposed on to the lateral walls by pitched roofs.
The force imposed by pitched roofs on the lateral supporting walls are vertical directed towards the ground with a slight lateral component pushing the external wall outwards. This is the reason for reinforcing lateral roof supporting walls with pillars or reinforced steel. This is a well known practice carried out in the design and construction of major buildings for centuries, and it is also present in majestic constructions like churches etc. These supporting reinforcing pillars can be either built externally or internally to the building. In our case, the reinforcing pillars are built internally. Hence, the external walls were designed and constructed to withstand any roof defect that could increase the lateral outward force imposed on the side supporting walls.
Summary of the two incidents.
1) The First occurred in September the 13th 2023 which caused the total immediate outward collapse of a supporting wall which in turn caused the collapse of the roof which it supported. This primary collapse in September was also the cause of the consequent second roof slow collapse the same year which started at the end of October 2023, which is referred to as referred to as “second incident” as below.
2) The second incident is consequential to the first incident and it involves the slow collapse on its own footprint of the second adjacent roof while the side wall parallel to and facing Harold Street remains completely intact and uneffected. This side wall of course shows no signs of fatigue or over-loading and it is expected to remain standing given its strong structure. This second incident started at the end of October 2023 and had been slow and progressive in nature carrying on collapsing slowly all throughout November 2023. At the end of January 2024 this slow roof collapse seems to have slowed down to a stop due to seemingly having reached a point of equilibrium. The structure is temporarily stable.
It is important to understand that the second incident is consequential to the first, and the second incident would not have occurred if the first did not. In other words should the side wall (parallel to and facing Castle street) did not collapse in September 2023 the whole structure would have remained intact and would have stood the test of time as it had done from its construction until September 2023. The cause of the collapse of the first roof in September 2023 and the slow collapse of the second roof was the primary collapse of the side wall in September 2023.
As we will see the wall collapsed and that caused a cascade of collapses in domino effect. Without the collapse of the main side wall collapse, the whole structure would have remained solid and stable as it had been since its original construction. Therefore, it is clear that the cause of these collapses is the primary collapse of the side supporting wall. Whatever caused the first supporting wall to collapse is the cause of all the other collapsed following it.
None of these collapses involved or seem to have compromised the main two-story building attached to it.