Can You Hang Sheetrock Over Existing Sheetrock on a Ceiling?

Locate Joists

• If you’re installing a double layer of drywall on a new ceiling, you’ll know the location of the joists, because you won’t tape out the seams before hanging the second layer. On an existing ceiling, however, you can’t see the joists, so use a stud finder to locate them. Ceiling joists typically are spaced 16 or
  24 inches apart. Once you find one, it’s simple to measure and locate the rest. Pop a chalk line over every joist for reference.

Screw Length

• The standard rule when hanging drywall is to insert a screw that is 1 inch longer than the drywall is thick. For example, if the first drywall layer is 1/2 inch thick, use 1.5-inch screws to attach it to the joists. When you install the second layer, which adds another 1/2 inch of drywall, use 2 inch screws. Every screw must hit a stud to hold the panels securely.

Panel Layout

• On an existing ceiling where you can’t see the original drywall panel layout, position the panels perpendicular to the joists, and install the largest panels you can safely maneuver. A drywall hoist is essential for reducing the weight burden from your neck and shoulders, and you can rent one from a construction rental store. In the case of a fire-rated ceiling, where you will install both layers of panels at the same time, you must stagger the seam joints. Because local codes may vary, contact your local building authority for additional regulations before installing a double fire-rated ceiling.

Soundproofing

• A double layer of drywall on the ceilings and the walls can reduce noise transmission from floor to floor and from room to room. If you’re hanging a double layer of drywall for noise reduction, you can apply a 1/4-inch bead of silicone over the joists before attaching the panels. The silicone adds a greater measure of noise reduction by creating a small air space between the panels along the seams where they attach to the joists.