My gut reaction to this question is don’t. After putting in hours of hard labor on a re-grout, only to realize the job is five percent done, a demo hammer starts looking mighty good. Must—resist—hammer.
Re-grouting is often a difficult, tedious, time consuming project. There’s a high probability you’ll chip the edges of some tiles, no matter how carefully you work. But that’s not especially helpful, so if you’re contemplating re-grouting, we need to determine why.
Is your grout stable, not cracking or crumbling?
If so, these are some reasons I’ve heard for wanting to re-grout.
“The grout is hopelessly stained and won’t come clean no matter how much I scrub.”
“The grout is blotchy, dark in some areas light in others.”
“I’m totally sick of the grout color.”
Changing the color of grout doesn’t always require re-grouting. Most places that sell tile also sell grout stains. When compared to re-grouting, staining is a simple, effective, and long lasting solution. Some grout stains come with a long warranty. As with any product, read the customer reviews before purchasing.
Before staining, the grout will need to be thoroughly cleaned. Follow the stain manufacturers recommendation for specific cleaning requirements. Generally you’ll need to remove any mold, soap scum, or other material that will keep the stain from penetrating into the grout. If the grout has been sealed, you’ll need to use a tile cleaner capable of stripping sealer. Cleaners for every day use don’t usually strip sealer. Heavy duty tile cleaners will indicate in the instructions if they strip sealer.
I prefer applying stain to grout joints with a cheap paint brush. It’s not necessary to paint the joints perfectly without getting any on the tile. Keep a damp towel handy to wipe excess stain from the tiles before it dries. The stain soaks into the grout and generally won’t wipe off while cleaning-up the excess. Grout stain works well with most glass, glazed ceramic, and porcelain tiles.
Unglazed tiles, tiles with anti-skid, or other rough finishes may hold onto the stain. Stone can be problematic when staining grout. Unpolished stone will most likely absorb the stain. Polished stone may or may not absorb stain. The only way to know for certain if your installation is a good candidate for staining is to test an inconspicuous area.
Is your grout cracking or crumbling?
If so, you’ll need to do some investigating before you tackle re-grouting. Cracking grout can be a sign of a larger underlying problem. If your problem is occurring in an area near a water source, determine if you have a leak. Colored grouts generally appear darker than normal when wet and can sometimes indicate a leak. That’s how I realized I had a dishwasher leak before it became a serious problem.
Moderate leaks typically don’t go unnoticed for too long, but a small long-term leak can quietly rot a wooden sub-floor. An unstable or deteriorating sub-floor often first shows its presence in cracking grout.
Inspect the problem area for hairline fractures in tiles. If you find no fractures, gently rap the tiles with your knuckles, like knocking on a door. Well adhered tiles will sound solid. Loose tiles will sound hollow and sometimes rattle. Cracked or loose tiles typically (not always) indicate a bigger problem that re-grouting won’t fix.
If your grout issue is occurring on shower walls, use the same rapping technique to determine if the tiles are loose. It’s a common practice for some contractors to use drywall for shower walls. In a perfect world where a homeowner applied penetrating sealer to the grout every couple years, thoroughly inspected the grout for hairline fractures, and made repairs immediately, drywall might be adequate. In reality, water almost always seeps through tiny gaps, soaks into and destroys the drywall. This problem usually causes grout to crack and fall out, shortly before tiles begin falling off the wall.
If you’ve determined the substrate backing you tile is sound, and your tiles are properly adhered, re-grouting is a legitimate way to extend the life of your tile installation. If most of your grout is sound but you have a few trouble spots, you may want to consider re-grouting only the problem areas and then applying grout stain to the entire installation to provide a uniform color. The less grout you have to remove the better.
If your joints are large enough, 1/4 inch or more, using an electric multi-tool with a grout blade will make your job less painful, not painless.
If your joints are too small for a multi-tool, determine the hardness of the grout. You may have stored-up a load of good Karma, have someone upstairs who likes, be overdue for a good break, or just be an exceptionally lucky person, and the grout will be soft. If so, scraping it out with a disposable blade utility knife is a viable option. This is a technique I’ve used with deteriorating unsanded grout. The advantage in using a utility knife is the thinness and flexibility of the blade. Extreme caution is still necessary, but I’ve found that I have less chipping this way.
Home improvement stores sell a variety of muscle-powered grout saws and scraping tools. Unfortunately I can’t recommend one that will make your job easy. Pick the one that best fits your grout joint thickness. Be extremely careful not to twist the tool between the tiles. A tiny amount of pressure from a wedged or twisted tool can easily result in a chipped tile. My point here is not to be discouraging, but to emphasize the need for a delicate touch. Properly installed grout is hard. No matter what you use to remove it, you’re in for a workout.