Q. We've been called back to repair the ceiling of a vacation-home addition we built last year. The 5/8-inch fire-rated drywall ceiling is covered with 14 inches of blown-in insulation. All the tape joints performed well except those within a 6-foot radius above the wood stove; they've lost adhesion and curled. The Northern vacation home is unheated when not occupied and undergoes 12 to 15 heating and cooling cycles annually. What caused this problem, and what's the best way to fix it?
A. Myron Ferguson, a drywall contractor in Galway, N.Y., responds: Framing, drywall, joint tape, and compound expand and contract at different rates. Under normal conditions, these differences don't amount to much, but when you factor in all those heating and cooling cycles and the heat from the wood stove, the joint failure you've observed is not that surprising. Under sustained temperatures of more than 125°F, drywall, compound, and tape gradually deteriorate, while tape can crack, pop loose, or peel when panels shift significantly due to structural movement.
Remember that problems can also arise during installation. For example, under very dry conditions (which can be caused by direct sunlight as well as by the heat from a fireplace or wood stove), freshly taped joints can dry out too fast and the tape can come loose. If too much compound is left behind the tape, or if the compound is thinned down too much, taped joints become weaker and more susceptible to cracking.
To fix your problem, try removing the loose material and retaping with an extra-strength mesh tape like Perfect Finish FibaTape (800/762-6694, www.fibatape.com) and a setting compound. However, I can't say for sure that this will hold up under the conditions you describe. You may have to cover the area with a suspended ceiling and fire-resistant ceiling tiles, which don't depend on any heat-sensitive material or adhesives to stay in place.
