How to Frame Basement Soffit

Basement soffit offers a means of hiding ductwork, plumbing and similar building infrastructure. In general terms, soffit is exterior ceiling, such as that under a roof's eaves. In the case of a basement, soffit is framework covered with drywall that covers up the items that hang below the true basement ceiling. A soffit doesn't bear any weight other than the drywall that goes around it, but you still need a solid framework to ensure the soffit doesn't sag. Accurate measurements allow you to build a soffit that fully covers the items on the ceiling without unnecessarily sacrificing head space in the basement.

Tape measure
1/2-inch plywood
2-by-2 lumber
Drill
Screws
2-by-4 lumber
Nails
Hammer
Chalk line

Instructions

- 1
  Measure from the bottom of the ceiling joists to the bottom of the lowest point on the ductwork. Add 2 inches to this measurement to provide enough clearance in the soffit.
- 2
  Measure the width of the ductwork that you plan to enclose with the soffit. Add 5 inches or more to the width to account for the framing and leave some clearance inside. If the ductwork runs near a wall, you also have the option of simply using the wall as the third side of the soffit instead of building another wall. In this case, the width of the soffit is the distance from the far edge of the ductwork to the wall.
- 3
  Cut 1/2-inch plywood to equal the distance from the ceiling to the bottom of the soffit as previously measured. Cut multiple pieces of plywood if needed to make the soffit long enough to cover the entire length of the ductwork.
- 4
  Cut 2-by-2 lumber to run the length of the soffit. Position the boards along the top and bottom edges of the plywood to create the frame of the soffit. The edge of the board should line up with the edge of the plywood. Drill pilot holes through the plywood and lumber before screwing the two pieces together.
- 5
  Cut 2-by-2 lumber pieces that run from the top to the bottom board on the soffit side. Nail these pieces every 16 inches to provide a framework for attaching drywall.
- 6
  Measure 2 1/2 inches away from the ductwork and snap a chalk line there to guide the installation of the soffit side. Attach the soffit to the ceiling joists using 3-inch screws. Drill pilot holes and screw into every joist. The plywood goes toward the ductwork, with the 2-by-2 boards facing away from the ductwork.
- 7
  Attach a 2-by-4 board to the side wall so the bottom lines up with the bottom of the soffit side. Nail this board into the wall studs. If the ductwork isn't close to the wall, build another soffit side that is identical to the first with plywood and 2-by-2 boards. Install it to the ceiling joists the same way you did the first side.
- 8
  Cut additional 2-by-2 boards to create the bottom boards of the soffit, known as the lookouts. Nail these boards between the bottom edges of either side of the soffit with 16-inch spacing. The lookouts need to be flush with the bottom edges of the soffit sides to finish the framework. The soffit is now ready for drywall.

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