By Michael Frech, Sullivan Engineering LLC
Even though parapets are often the easiest architectural feature to monitor and maintain, they are often the most neglected. There are key reasons why these short walls extending above the roof deck experience the most deterioration from weathering.
A standard façade wall is only exposed to the weather on the exterior face of a structure. At the parapet level, the façade cladding material is exposed on three sides: the exterior, the interior and the top. The parapet also has detailing that is integrated into the roof or other waterproofing membrane. This increased exposure and integration provide more opportunities for water infiltration and increases the rate of deterioration.
Older and Current Parapet Designs
The time period in which the parapet was designed often determines the severity and pace of deterioration. Older designs often focused on keeping water out, and did not provide a method for allowing water to exit the parapet assembly. Current designs tend to incorporate redundancy, which means the design prevents water entry and allows water to exit the parapet assembly before it causes deterioration.
Parapets can often be easily inspected from the roof. Unfortunately, this is usually done only when an interior leak is reported. Once there is internal water infiltration however, severe damage to the parapet, the roof assembly or even to the structural elements of the building could be possible. During their seasonal roof inspection, building personnel should also inspect the parapet. Check for deteriorating mortar or sealant in the seams or joints of the coping at the top of the parapet. Manually test the coping material to ensure none of it is loose. Inspect the interior face of the parapet for signs of deterioration such as failing mortar or sealant joints, vertical staining from the coping to the roof, and the integrity of the cladding material itself.
The detail between the roof base flashing and parapet should also be inspected. This detail is often altered from its original design when a roof has been replaced. The new roof base flashings might be surface-mounted, therefore covering the original through wall flashing and weeps that were designed so water could exit the parapet assembly. Building personnel should check the integrity of the flashing material and locate the weeps. The weeps should be positioned above the roof base flashings and be clear of any debris.
Setbacks in the façade will allow for a closeup inspection of the exterior face of the parapet from the roof. If the building does not have setbacks, an inspection using binoculars should be performed from ground level. Any vertical staining, deteriorated mortar or sealant, displaced brick or bowing lintels should be noted.
If any of these conditions exist, water is probably infiltrating the parapet. A design professional should be retained to perform a more comprehensive inspection and to determine the proper method of restoration. Being vigilant in your seasonal inspections and proactive in your restoration efforts can be the difference between a simple repointing project and a total parapet replacement, structural repairs or a roof replacement.
Michael Frech, Sullivan Engineering LLC