How To Seal Air Ducts With RCD Mastic

Seal Air Duct Leaks & Save Energy

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.  

Wipe Duct Clean

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.

Brush RCD Mastic Onto 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.

Reinforce Joints & Seams


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