Q: How do I repair grout on a tiled wall or floor?
A: First, it’s important to understand why the grout needs to be repaired. If a patch of grout in the middle of a dry floor crumbles and breaks loose, the floor might have flexed, and all you need to do is scrape out the loose parts, clean the area thoroughly and fill it in with matching grout or color-matched caulk, which will stay slightly flexible and might stay in place better.
The other extreme is a situation where sections of grout on a shower wall have come out and individual tiles are loose. Those are signs that water probably has gotten into the wall behind the tile. Especially if the surface behind the tile is a type of drywall, repairing the grout is a waste of time. You need to remove the tile and start over, or you could end up with rotting walls and musty odors that don’t go away.
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Or maybe it’s something between those extremes: The grout is intact, but it’s hopelessly stained and hairline cracks are beginning to show. In that case, you should scrape out the old grout and install new. If you want to patch only a small area, you might be able to remove the old grout with a simple tool called a grout saw, such as the QEP handheld grout saw, which comes with two blades (one steel, one carbide) for $8.45 at Home Depot. The idea is to start with the steel blade, which is less likely to scratch tile, then switch to the carbide blade to clean deeper and remove stubborn sections. Scraping out grout by hand minimizes the risk of damaging tile.
If you have a lot of grout to remove, though, you need to get a tool with more power. It’s possible to fit a reciprocating saw with a grout-removal blade, such as the Milwaukee grout rake ($13.99 at Home Depot). But unless you’re skilled in controlling the tool, it’s easy to grind into tile. If you have a rotary tool, often referred to by the brand name Dremel, it will also work if fitted with a grout-removal bit.
But the best option for most homeowners is an oscillating tool, also known as a multi-tool, with a blade designed for grout removal. Ryobi’s 18-volt cordless model with a battery and charger lists for $144 at Home Depot, but if you already have a battery for another Ryobi tool, you can get just the tool for $59. Most brands offer similar deals for sharing batteries among tools. Grout-cutting blades for oscillating tools come with either carbide or diamond grit and generally fit any brand of tool. One nice feature: The blades generally have one flat edge, without grit, so you can cut grout right up to the edge of an adjoining surface without damaging it. (DeWalt’s carbide oscillating blade is $13.46 at Home Depot.)
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Clean the tile thoroughly before you tackle grout removal, and let everything dry. If you’re working on tile above a bathtub or countertop, tape on a protective layer of plastic to prevent scratches. Then, while wearing eye protection (and ear and breathing protection if you’re using a motorized tool), remove all the loose grout and as much sound grout as you can — at least to a depth of two-thirds. Brush out the gaps and vacuum up the debris.
The kind of grout you need depends on the width between tiles. Gaps narrower than ⅛ inch, common on walls, need unsanded grout. Wider gaps need sanded grout, but check labels, because grits vary to accommodate joints of different widths. (Wider joints need coarser sand.) Both sanded and unsanded grouts are cement-based or latex-modified products. You’ll also find epoxy grout, which is much trickier to apply but resists stains and moisture and thus might be a good choice for regrouting a shower floor or countertop. If you opt for epoxy, read the application instructions carefully and consider choosing a color that is close to matching your tiles, so if you leave some smears, they won’t be as noticeable.
Prepare the grout as the package recommends, and mist the tiles with water if the directions say to do so. For cement-based or latex-modified grouts, it’s safest to work on only about three square feet at a time. While wearing rubber gloves, press a rubber grout float loaded with grout against the wall or floor, and work the grout into the crevices by making passes in different directions, including diagonally. Wipe off the excess with the edge of the float or with a masonry sponge that you rinse frequently and wring out well. Immediately move on to adjoining areas. When the whole surface is grouted, wipe down everything again with a clean, damp sponge. Allow the grout to dry until a haze covers the tiles, then wipe down again. Once you have let it cure as long as the grout package recommends, wipe off any remaining haze with a clean, dry towel.
Apply a grout sealant to keep water from penetrating and to make your new grout easier to keep clean.
Have a problem in your home? Send questions to localliving@washpost.com. Put “How To” in the subject line, tell us where you live and try to include a photo.
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