Sheet Metal Worker how-to
How to Seal Ductwork with Mastic
Sealed ducts save energy and meet code leakage requirements.
Quick answer
Sealed ducts save energy and meet code leakage requirements. In short: clean; apply; embed, then complete the remaining steps below.
Step by step
Clean joints of dust and oil.
Apply mastic over the seam with a brush or gloved hand.
Embed fiberglass mesh tape in wide gaps.
Cover screws and corners completely.
Let the mastic cure before insulating or testing.
Safety reminders for sheet metal workers
- Wear cut-resistant gloves and handle metal edges carefully
- Use hearing and eye protection around machinery
- Follow ladder, lift and fall protection rules
- Lock out machines before clearing jams or changing tooling
Key terms
Gauge · Pattern layout · Brake · Pittsburgh lock · S-and-drive · Takeoff: see the full sheet metal worker glossary.