Many homebuyers will judge the overall quality of a home by the quality of the wall finish. Since drywall makes up a large portion of the interior, flaws are hard to miss.
Many issues first appear in the area over a joint—the place where the edges of two drywall sheets meet. When a joint is visible, it detracts from the look of the wall or ceiling, potentially leading to callbacks, increased costs, and unhappy customers.
Cause 1:
Crown in the joint compound
Crowns are built-up mounds of joint compound at joints. A crown appears as a raised area along a joint. Crowns are typically caused by poor feathering of the joint compound; properly feathered joints should require little or no sanding.
Solution
Feather each layer of joint compound more than the last, and allow proper drying time between each step. A correctly finished tapered joint should have these layers: bed coat and tape, first coat 4" to 6" wide, second coat 6" to 8" wide, and third coat 10" to 12" wide. A correctly finished butt joint should be feathered out as much as 16".
Cause 2:
Insufficient joint compound coverage
Applying an insufficient amount of joint compound at a joint will result in a valley between drywall sheets, which is visible as a shadow in cross light.
Solution
Before taping, apply a sufficient bed coat of joint compound to create a squeeze out on both edges of the tape. Areas of larger fill may require retouching before the next coat. Using a lightweight compound or a setting-type compound may also reduce shrinkage. Feather each layer of joint compound more than the last, and allow proper drying time between each step. A correctly finished tapered joint should have these layers: bed coat and tape, first coat 4" to 6" wide, second coat 6" to 8" wide, and third coat 10" to 12" wide. Butt joints require greater feathering, because the tape joint is on top of the sheet instead of in the factory edge.
Cause 3:
Drywall sheets installed too tightly together
When drywall sheets are installed too tightly together, any expansion of the sheets will create a visible ridge at the joint. When the sheets move apart, they stretch the tape; when they move back together, the tape buckles. A ridge may also form when the sheets gain a lot of moisture, softening and expanding, causing the factory edge to compress and ridge.
Solution
Drywall sheets should gently touch each other. The natural irregularities of the drywall will create small openings between the sheets that allow joint compound to squeeze through to the back. Hang sheets as flat as possible to avoid edge compression.
Cause 4:
Misaligned framing and changes in framing direction
Misaligned framing can occur where multiple framing components are combined together, such as at headers, sills, joists, ganged studs, or around stairwells. It can also occur where a series of roof trusses don't align along the plane of the ceiling. Placing joints over misaligned framing may lead to visible joints. It's difficult to correctly finish an uneven joint with joint compound. Changes in framing direction, such as where a girder truss is installed to support a hip roof, can also be problematic in the area where the two components are connected. Independent movement of these components will be emphasized at this connection point.
Solution
Inspect the framing for misaligned framing members. Check studs and joists that are ganged together for misalignment. Check roof trusses for alignment along the plane of the ceiling. If they're misaligned, have them shimmed to create a flat surface for the drywall. Also, check the framing at headers and sills for misalignment. Drywall joints should be transitioned at least 2' from a change in the direction of the framing.
