What thickness must plastic be for ductwork?

• A. 1/16 inch
• B. 1/4 inch
• C. 1/8 inch
• D. 1/8 inch or thicker

Answer: (D)

Plastic ductwork has to be thick enough to keep its shape and resist damage during handling and in service. The minimum for rigid plastic duct is 1/8 inch, which gives the needed rigidity to prevent sagging, deformation, or leaks at joints under typical air pressures. Thinner material, like 1/16 inch, would be easy to dent or tear and wouldn’t hold up well. A thickness of 1/4 inch is allowable but thicker than necessary for most cases, adding weight and cost. Saying 1/8 inch or thicker communicates the required baseline while allowing for designed extra strength where needed.