How To Seal Air Ducts With RCD Mastic

A – CLEAN DUCT SURFACE: Use a cloth to wipe dirt, dust, and debris from the surface of the duct. If oil or grease is present, wipe clean with a damp cloth.

B – JOINTS WITH GAPS LESS THAN 1/4 INCH: Coat the entire joint with a 2” wide by 1/16 of an inch thick continuous strip of mastic, using the end of the brush to work the mastic into the joint.

C – JOINTS WITH GAPS GREATER THAN ¼ INCH: Reinforce with RCD Corporation’s Glasscoat (fiberglass mesh) in addition to mastic. Apply a coat of mastic per (B) above, then embed Glasscoat into this first coat of mastic and finish by applying a second coat of mastic filling the mesh entirely.