How to Build a Soffit Around Heat and A/C Ducting

HVAC duct carries heated and cooled air throughout a house to vents in the walls, the floors and the ceiling. Builders usually hide duct in the cavities between wall studs and ceiling and floor joists. But in instances where hiding duct in walls, floors or ceilings is not feasible, hiding it in a soffit is a popular alternative. Building a soffit requires basic carpentry skill, as well as the ability to hang and finish drywall.

Tape measure
Hammer or nail gun
Circular or hand saw
Nails
Two-by-four lumber
Corner bead
Half-inch drywall
Utility knife
Drywall nails or screws
Drywall knife
Joint compound
Medium-grit sandpaper

Instructions

- 1
  Locate the closest stud on each side of a vertical duct and the closest joist for a horizontal duct. Nail a row of two-by-fours running parallel to the duct to the studs or joists. The two-by-fours should run the length of the duct and will serve as support for the soffit.
- 2
  Cut several two-by-fours into 12-inch boards. Nail these pieces to the support boards at 24-inch intervals on each side of the duct. Each piece should be directly across from a corresponding piece on the other side of the duct. Attach another piece that crosses the duct and connects the corresponding pieces to form a box around the duct.
- 3
  Measure the box and cut drywall to fit. Apply a thin coat of joint compound along the wallboard seams using your wallboard knife. Press a strip of drywall tape into the compound along the seams, and press a strip of corner bead onto the corners. Apply a second coat of compound, and let the mud dry overnight. Apply an additional coat of compound, let it dry, then sand with medium-grit sandpaper to smooth.

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