Proper EPDM Lap Sealant Application: Mound it up for Long-Term Performance

Lap Sealant is required around the edges of Carlisle SynTec’s Pressure-Sensitive Elastoform Flashing and is an important part of the flashing detail. For long-term performance of the lap sealant, it is best to use the pre-formed plastic lap seal feathering tool provided in every box of Pressure-Sensitive Elastoform Flashing. The lap seal feathering tool has a beveled V-shaped groove to create a rounded mound of lap sealant centered over the flashing edge.

A common mistake to avoid when using a cardboard feathering tool is to flatten out the lap sealant bead from using too much pressure or not forming a big enough groove. When lap sealant is flattened out to a thin layer, it is more prone to cracking from the natural expansion and contraction forces that occur on a roof. A major benefit of using the plastic feathering tool is that it doesn’t deform with added pressure, so you still achieve a rounded mound of lap sealant.

To ensure proper application, please follow these steps below which are also outlined on Sure-Seal and Sure-White Lap Sealant product data sheets:

1. All surfaces to be sealed must be dry and free of oil, dust, or other foreign materials.
2. Clean the area to be sealed with Weathered Membrane Cleaner to remove all foreign materials.
3. Apply a 5/16” (8mm) bead of Lap Sealant along the outside edge of flashing.
4. Use the plastic feathering tool to form a rounded mound of sealant directly over the flashing edge.
5. Lap sealant may be applied immediately to Pressure-Sensitive Elastoform Flashing.
6. Lap sealant must be applied and feathered by the end of the working day.

For more information on proper application of EPDM lap sealant, please contact your local Manufacturer’s Representative.