Ask the Builder: How to repair cracked backsplash grout
Q: The grout line between my kitchen granite countertop and the tile backsplash has cracked for the umpteenth time. Each winter the crack appears, and each year I re-grout it hoping it will be the final time. Am I using the wrong grout? How would you repair this, and why does the crack disappear on its own in the summer? I have the same issue with other cracks around my home that mysteriously open and close depending on the time of year. --Gary K., Columbus, Oio
A: I swore off almost all gambling years ago when my wife caught me trying to make double-or-nothing basketball shots with my young son. She made me pay the $100 I was up to when she opened the garage door and discovered me frantically trying to make a basket. Of course, he ratted me out because he thought he was rich. I’m pretty certain he still has that money, and the shameful incident is brought up with regularity at family gatherings!
That said, I’m willing to bet that a lot of my readers have a similar issue in their homes with cracks that appear in the winter months and then disappear in the summer. It happens in my own home.
The source of the pesky cracks is water vapor. You won’t find these cracks in well-built motels made from concrete and steel. Concrete and steel are very stable and don’t change shape when wet. You find them in structures built with wood located in climates with hot and humid summers.
Wood is hygroscopic. This means that it changes in size in response to moisture content. Think of a piece of wood like a synthetic sponge. When you get it wet, it swells. When it dries out, it shrivels. The change in size can be fairly dramatic.
This shrink/swell issue isn’t as bad in older wood-frame homes. I’m talking ones built using old-growth timber from the late 1800s or early 1900s. Modern framing lumber has been hybridized to grow faster, and the light-colored spring-wood bands of wood fibers are much larger than the darker summer-wood bands when the tree growth slows because of the lack of water and oncoming winter.
This newer hybridized lumber is much more reactive to changes in water content than the wood of old. It swells and puffs up slowly as the humidity rises in your home. Here in the northern hemisphere, by the end of August the wood framing in your home is like your lungs after you take an enormous inhalation of air.
As your home transitions to January and February, this water is liberated from the lumber and the cracks bloom in your home like flowers in the desert after a 1-inch rainfall. The water in the wood is pulled out by the drier winter air in your home.
In my opinion, the best way to deal with these cracks is in the dead of winter. Stop using hard grout and switch to the best caulk with the most elasticity. This characteristic is often called out on the label of the caulk. You'll discover high-quality caulks at a home center or large hardware store.
Remember, the more expensive the caulk is, the better it is (usually). Why? In these cases, the manufacturer puts in better ingredients that almost always are more expensive.