How to Create a Ceiling Around Ductwork

Measure the length, width and depth of the duct so that you know how big to make the soffit. Add 2 inches to the width and depth of the soffit. If one side of the duct is within a few feet of the wall, consider extending the soffit to the wall, rather than building a second side to the soffit.

Screw a 2-by-4 to the wall if you are extending the soffit to the wall. Place the board on the wall 2 inches lower than the bottom edge of the duct. Use masonry screws for a concrete wall and galvanized screws for drywall. Skip this step if the duct is in the center of the room and you're building a soffit box with two sides.

Cut side boards for the soffit from 1/2-inch plywood.

Measure and cut 2-by-2s that are as long as the duct. Cut two boards for each side of the soffit.

Screw a 2-by-2 to the top and bottom edges of the 2-by-2s with 1-5/8-inch screws to make the side panels of the soffit. If you're attaching the soffit to the side wall, only build one side panel, as the wall doubles as the second side panel.

Hold the first side panel against the ceiling joist with an assistant's help, and screw it to the ceiling joist with 3-inch screws. Install the second side panel if you have one. Hang the side panels so that the edge with the 2-by-2s faces away from the duct.

Measure and cut the lookouts to fit between the inner edges of the two side panels, or between the side panel and the 2-by-4 on the wall. The lookouts are strips of 2-by-2 that run across the bottom of the soffit; the drywall is attached to them.

Place the lookouts along the bottom edge of the soffit, using one lookout every 16 inches. If the soffit has two side panels, drive the nails through the 2-by-2s on the side panels and into the ends of the lookouts. If the soffit is attached to the wall, use the above method to attach the outer edge of the soffit, and toenail the other end of the lookouts to the 2-by-4 on the wall. Drive the nails through the end of the lookout and into the 2-by-4 at a 45-degree angle.

Measure and cut 1/2-inch drywall to fit on the sides and bottom of the soffit.

Attach the drywall to the framing with drywall screws, using one screw every 6 inches.

Nail metal corner bead to the bottom corners of the soffit. The corner bead covers the joint where the different drywall surfaces meet, creating a smoother corner.

Cover the metal corner bead and joints where the drywall sheets meet with joint compound and drywall tape. Press the drywall tape into the joint compound with the putty knife. Allow it to dry overnight.

Sand the joint compound with fine-grit sandpaper until the surface is smooth. Wipe the dust off of the soffit with a dry rag.

Place two more applications of drywall tape and joint compound onto the soffit, following the same process you used when installing the first application.