- Q. We have had good luck using the old-fashioned technique for exterior stucco: 1/2-inch plywood, felt paper, wire mesh, then 1 inch of plaster in three coats. Last year our luck ran out. We built a house on a hill where the wind just didn’t stop. A year later, one face — the gable end of a two-story two-car garage — has many hairline cracks. The stucco sub wants to put a heavy fiberglass tape over the cracks and re-stucco that face. Is this a good solution?
A.Steve Thomas, a stucco industry veteran, responds: I have to admit (even after a phone call to the builder), this one has me stumped. There are several possible causes for the cracking. The prolonged high winds could have caused the finish to craze, but why on just one wall plane? The framing lumber could have been abnormally dry, then "stretched" as it picked up moisture — but ordinarily the 1/2-inch plywood should have prevented cracking. Conversely, the lumber could have been excessively wet, then shrank as it was protected from the rain. But again, the plywood sheathing should have restrained movement enough to prevent cracking. It’s also possible that the 1/2-inch plywood could have been butted too tightly, causing it to buckle at edges and cracking the finish.
Another possibility is that the wind lifted the roof and wall, or caused the wall to rack (not uncommon in garage walls because of the large openings and consequent lack of lateral bracing.) I asked the builder whether impact loads or heavy loads in the attic floor could have played a part, but no such impact occurred, and there’s no floor in the attic yet, so no loads.
The stucco itself could have been mixed way too rich (too much Portland cement), which might cause shrinkage cracks. But again, what are the odds of this occurring on just one face?
My best advice to the builder is to try to stiffen the gable end by installing hurricane straps at the top and bottom of each stud and installing metal X-bracing on the interior of the wall. Then I would accept the stucco contractor’s offer to span the cracks with mesh tape and refinish the affected wall plane, in hopes that the resulting color will match the adjacent walls acceptably. It would probably also be a good idea to secure the homeowner’s signature that this attempt on the contractor’s part is the last free effort to solve the problem.