Kate Royce

CM Site Wall Detailing For Moisture

4 posts in this topic

To give a more defined response, can you please provide more clarification on what you define as a site wall?

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Site walls are in many ways a unique assembly Kate. Unlike the typical exterior masonry wall, which is directly exposed to the weather on only one surface, site walls have direct exposure on both sides as well as the top; making them more akin to parapets from an exposure perspective and therefore more susceptible to moisture intrusion and potential efflorescence concerns. Unlike parapets, however, it is pretty rare to flash the base of site walls and fences...not that doing so is technically unsound, but instead it typically doesn't provide the same level of performance-to-cost benefit as would flashing the exterior walls of a masonry building would. 

Instead, site walls are typically detailed with a focus of minimizing moisture intrusion rather than detailing for draining any incidental moisture that may accumulate within the assembly. For the vertical wall surfaces, this is accomplished by using and integral water repellent in the units and mortar and good workmanship and tooling of the mortar joints. The top of these assemblies tends to be where most moisture infiltrates, leading to potential efflorescence. To mitigate moisture intrusion at the top, caps should be sloped to prevent standing water from accumulating and provided with an overhang and drip (kerf) to prevent water from draining under the cap or down the surface of the assembly. In extreme exposure conditions, one can also consider filling the top course of units below the cap with mortar or grout to provide an added layer of protection.

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