Tips for repairing failing drywall seams

Rob Robillard – Globe Correspondent

November 8, 2018 4:31 pm

QQ The length of a first drywall seam in our home needs to be repaired before we repaint. What would be the best way to do this?

Mike York, Maine

A. Looks like the paper tape of the ridge seam is defective. A common mistake at this point is called “grouting” or “beading” but I can’t tell from the photo if you have that or not. Joint grooves are a uniform fine deformation line that occurs on plasterboard joints. (Drywall is a sheet of plasterboard.) Factors that help to do this are:

■ Wood shrinkage

■ humidity

■ heat / cold

■ Bad workmanship

Any of the above reasons can cause this. The common denominator is the compression of the edges or ends of the finished plasterboard.

Your photo shows a clear flaw in the paper seam tape. You may be able to remove this and repeat with a mesh tape. Problems can arise if the initial layer of sludge dries before the paper tape can be fully embedded in it. This is often the case when recording is done on a hot summer day. Over time, the tape will separate from the wall. Bad application is likely the number one cause of a tape failure.

Note: In order to repair drywall seams, it should be possible to stabilize the plasterboard system. You should wait until after a full heating / cooling cycle to make repairs. During this repair, make sure the room is warm and dry.

Repair steps

■ Lightly sand the ridge and take care not to damage the embedded joint reinforcement tape.

■ If you find that only the tape has failed, use a utility knife to remove it and put a foot past the damage.

■ Sand the area smooth and stop just before the drywall surface. Do not sand down drywall paper.

■ Retape. I like self-adhesive fiberglass mesh tape.

■ Fill the surface above the joint with flooring or general purpose compound and feather as wide as necessary to get a substantially flat surface.

■ Let the connection dry for at least 24 hours.

■ Apply a second coat if necessary.

■ After the joint is dry, you can lightly sand it to feather the edges and remove trowel marks.

■ Apply primer and paint the entire ceiling (yup, the entire ceiling).

Rob Robillard is a general contractor, carpenter, publisher of AConcordCarpenter.com and head of a joinery and renovation company. Send your questions to [email protected] or tweet them at @robertrobillard. Subscribe to our free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp.

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