· by Michael Blair, Nashville's Tile and Stone
Middle Tennessee winters are not long, but they cross the freezing line again and again, often freezing at night and thawing by afternoon. For tile and stone outside, every one of those cycles is a test. Water that has found its way under a tile or into a cracked grout joint expands when it freezes, lifts a little, lets more water in, and does it again the next night. The first frost here usually comes in late October or early November, and what gets sealed or reset before then decides how the porch looks in spring.
Where the water gets in
Cracked or missing grout is the obvious entry point, but not the only one. The joint where the tile meets the house wall, the edge of a step where tile wraps the nosing, and the perimeter where porch tile meets a column base all open up as the slab and the house move at different rates. Clay soil under a Nashville porch slab swells in a wet winter and shrinks in a dry summer, and the tile rides on top of that.
A porch without enough slope toward the yard keeps water sitting on the surface after every rain. On a covered porch that seems protected, wind-driven rain and water running off the steps still reach it, and standing water in a low corner is where freeze damage starts.
A fall walk-around
Tap the tiles with the handle of a screwdriver and listen. A hollow sound means the tile has lost its bond, and water will find the void. Look for grout that is cracked, crumbled or missing, and for hairline cracks that run through several tiles in a line, which usually follow a crack in the slab below. Check the step edges, where tiles take the most traffic and the most water.
Look at the stone too. Some limestone and slate sheds thin flakes from its face after a winter, called spalling, when water soaks in and freezes. Flaking that has started will continue, and the stone underneath is softer and more open than the face that came off, so each winter takes a little more. Note which pieces are affected now; it tells you whether a sealer is worth trying or whether those pieces are headed for replacement.
- Hollow-sounding tiles, especially on steps
- Missing or crumbling grout joints
- A crack running in a line across several tiles
- Gaps where tile meets the wall or a column
- Low spots that hold water after rain
- Stone faces that flake or shed
What is worth doing before it freezes
Loose tiles on steps come up and get reset now, with a setting material rated for exterior use, because a loose step tile is a trip hazard as well as a water problem. Missing grout gets replaced, and the perimeter joints against the house get a flexible sealant rather than grout, since grout there cracks every season. Porous stone and cement grout can be sealed once they are dry, but a sealer only helps on material that is already sound.
Setting and grouting products have minimum temperatures in their instructions, and many need several days above that to cure. That is a practical reason to do this in late September and October rather than waiting for a mild week in December.
What to leave until spring
A crack running across a line of tiles that follows a crack in the slab is a structural movement problem, and regrouting it only hides it for a season. The right repair usually means cutting out the affected tile, dealing with the slab crack with a movement joint or an uncoupling membrane, and resetting. That is a bigger job and better done in dry, warm weather.
Over winter, keep the surface clear of standing water and avoid rock salt on tile, stone and grout. Sand gives grip without the damage, and many de-icers sold as safe for concrete are not safe for natural stone, so read the label.