TecTopics: Preventing roof damage from ice melts, moisture, and air infiltration

Ice melts
Ice melts that contain potash, urea, calcium chloride, and/or sodium chloride (common table salt) are safe to use with Carlisle EPDM, TPO, and PVC membranes, as well as exposed VapAir™ Seal 725TR. Be cautious if using ice melts on or around metal roof components! Ice melts will discolor copper, corrode and pit aluminum, and accelerate the oxidation (rusting) of non-stainless steel. It is the owner’s responsibility to take appropriate precautions to protect metal components.

If adhering new insulation directly to the surface of 725TR, make sure there is not excessive residue left behind from the ice melt products. The surface of the 725TR should be clean and dry when adhering the insulation. Use a garden hose to spray off any excessive residue left over from ice melt products.

Moisture damage and air infiltration
While occupancy-generated moisture is usually addressed through the use of a vapor barrier, construction-generated moisture can be reduced through a number of techniques. Sealing gaps between the structural deck and walls, as well as gaps around penetrations and at steel deck end laps, is critical. Using multiple layers of insulation, installed with the joints staggered, can provide an additional barrier against air infiltration and reduce moisture concentration in the roofing assembly.

Construction-generated moisture may also be reduced by careful project scheduling (coordinating roofing installations with the concrete pour schedule) and building dehumidification prior to occupancy. Refer to this SPRI advisory for more information about construction-generated moisture. 

On structural concrete decks, it is important to seal any gaps between the structural deck and walls and those around penetrations. Unsealed gaps allow hot humid air from within the building to infiltrate the roofing assembly and possibly condense during cold weather.

The same phenomenon can also occur on steel decks where gaps are not sealed or vapor barriers are not used. Refer to detail G-01: Deck-to-Wall Air Infiltration Resistance Barrier for more recommendations on preventing air infiltration.

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