Buckling drywall appears as a bulge or wide ridge that develops on a wall or ceiling. Due to the pull of gravity, a drywall ceiling is more likely to bulge than the walls, especially if the drywall becomes heavy with water. The repair process is involved, but even an amateur should be able to achieve high-quality results with enough time.
Probable Causes
There are two common reasons why drywall might buckle. The first is water damage. Drywall can't handle exposure to water, especially if it hasn’t been painted. The moisture causes deformation, leading to bulging and buckling. The second common cause is natural settling of a building’s wood frame, which can cause wood beams to push the drywall outward.
Wood Beam
If there is no water damage, a wood beam likely has caused the buckling. The simplest solution is to fill either side of the ridge with thick coats of joint compound. Use a broad drywall knife, which saves time by allowing you to cover wide swaths. Allow the compound to dry and add as many additional coats as are necessary to camouflage the buckling section of drywall. In between coats, sand the area until is smooth. Use 100-grit sandpaper for the first series of coats and 150-grit sandpaper for final sanding the area in preparation for primer and paint.
Repairing the Wood
Another option is to hire a professional contractor to shift the beam back into place. If you pursue this option, chances are the drywall will have to be removed, meaning you'll have to install and finish new drywall in its place. Depending on the problem, a contractor might notch the beam, force it straight and then brace the cut area with metal cleats. Shaving down the wood also might be an option.
Water Damage
If the bulge is due to water damage, you have two options. First, if the buckling isn't too pronounced, you might be able to hide it with thick coats of joint compound, just as you would to handle a wood beam problem. Before applying joint compound, test the area to see if the drywall shifts easily when you push against it. If it does, use a stud finder to locate the underlying wood frame. Install drywall screws until the surface is inflexible. If you’re lucky, installing screws will reduce the bulge, making the following repairs easier. After that, follow the same coating and sanding procedure as you would to handle a bulge caused by a wood beam.
Installing New Drywall
The other option for repairing water-damaged drywall is to cut out the deformed section and replace it with a fresh installation of drywall. After that, finish the new drywall by sealing it with paper drywall tape and joint compound. To hide the tape over the seams, apply several thick coats of joint compound, allowing each coat to dry. Sand as necessary to smooth the surface.
Lighting
If you don’t want to undertake a large repair project, changing the lighting scheme of the room can decrease the visibility of the buckled drywall. For example, if you have lights that are casting shadows perpendicular to the bulge, the damaged area will be more visible. Moving lights across the room or adding new light sources can make a deformed section less obvious.