Converting a cathedral ceiling to a standard flat ceiling is relatively easy because it requires very little demolition work, only the installation of new ceiling joists. Following the simple steps outlined below will result in a renovated ceiling that will be indistinguishable from new construction done by a professional carpenter.
Step 1 - Remove Existing Sheetrock From Cathedral Ceiling
Using the hammer claw, a nail puller, or flat crowbar, remove the existing sheetrock from the underside of the ceiling rafters until the wood frame is exposed. Be sure that every bit of sheetrock is stripped from the rafters and that every fastener, nail, and screw has been removed.
Step 2 - Prepare the Horizontal Ceiling Joists
With a measuring tape, measure the span of the new horizontal ceiling joists between the two walls that will bear the joists. Measure from the outside edge of the wall’s top plate to the outside edge of the opposite wall’s top plate. This will be the length of the joists. If the span is less than 10-feet, use 2x8 inch lumber for the new ceiling joists. If the span is 10-feet or greater, use 2x10-inch joists. With the circular saw, cut the joists to length, paying special attention to ensure that the cuts are square.
Step 3 - Install the New Ceiling Joists
If the top corners of the upright ceiling joists protrude through the plane of the roof, they will have to be chamfered. The joists should be aligned with each pair of opposing roof rafters. Install the joists so that the ends of the joists are on the same side of each pair of rafters and make sure the joists are perpendicular to the walls.
If there is a bow in the joists, nail the joists in place so that the bow is pointing upward. Over time the bow will flatten itself out and the joist will become straight instead of sagging below the ceiling plane. Using #12 nails, install the joists by “toe nailing” through each joist into the top plate, and through the face of the joist into the rafter.
Step 4 - Install Sheetrock Onto the Ceiling
Using sheetrock screws and a power drill with a Phillips head bit, install 4x8-foot sheets of sheetrock onto the bottom edge of the horizontal ceiling joists. Most wood frame houses are laid out at 12-inches, 16-inches or 2-feet on center.
Since the distance between the rafters and the ceiling joists are the same, the seams of the sheetrock should fall on the center of the joists. You now have a flat ceiling where there was once a cathedral ceiling. All that remains is to finish and paint the sheetrock.