Control the risk
Having identified the hazards and assessed the risks, you must manage those risks by implementing control measures. Risk control measures may include:
- designing walls to provide additional stability during the construction phase, such as adding sequential core filling with reinforcing or wall stiffeners (see figures 2 and 3)
- building walls at the same time as cross walls (see figure 4) or returns, or nailing-off frame ties in veneer construction, so that they support each other
- installing temporary supports (see figure 5)
- establishing stop heights to allow mortar to gain adequate strength before further construction – e.g. at lintel height
- storing materials away from unsupported masonry walls – i.e. not leaning materials against walls
- preventing inadvertent impact on walls by plant such as wheelbarrows, cranes or pallet trolleys – e.g. using dedicated travel paths and storage areas
- monitoring weather conditions – e.g. wind (see table 1), extreme temperatures and heavy rain – and amending work practices to suit
- stopping work if the existing top course is affected by rain to the point where the mortar bond strength will be impaired
- preventing the collapse of excavation behind masonry retaining walls
- not backfilling behind masonry retaining walls until they are permanently supported or (for self-supporting walls) have reached their design strength
- installing no-go zones, identified by barricades or other physical identifiers, to keep people outside of potential collapse zones. (This is not an adequate control measure for walls that could fall outside the construction site). Prevent such walls from falling under all likely conditions
- communicate the adopted risk control measures to all relevant people on site via site-specific induction training. Also communicate any changes to the controls – e.g. via toolbox talks.
Figure 2: Sequential core filling with reinforcing
Figure 3: Wall stiffener – open-ended blocks used to build around stiffener
Figure 4: Cross walls
Figure 5: Examples of typical types of temporary supports (not to scale).
(A) Metal triangular brace
(B) Timber triangular brace
(C) Metal prop brace