What to do about rust

Q: Our vintage 1926 bathroom floor is showing its age and some discoloration now that our building removed radiators. I cannot afford a full bathroom renovation. Can tile be applied on top of the old

Q: Our vintage 1926 bathroom floor is showing its age and some discoloration now that our building removed radiators. I cannot afford a full bathroom renovation. Can tile be applied on top of the old floor? Can the tile be painted?

Washington

A: Yes, tile can sometimes be applied over old tile, and tiled floors can be painted. But before you opt for either of those, you might want to try fixing the floor.

From the pictures you sent, the floor appears to be in good shape, except for where the radiator left rust spots. If that’s the case, why not try to remove the rust? Many rust removers are acidic, and their labels warn that they might etch tile, so try an alkaline rust remover, such as ConfiAd Rust Remover Gel ($37.95 at mystonecare.com). Instructions say to dampen the surface and apply the remover with a spatula or spoon. The gel changes color as it reacts with the rust. Within 10 minutes, wipe it away and rinse.

John Forguson, general manager of My Stone Care, said removing long-term rust usually requires multiple applications. “Put it on, and you’ll get the chemical reaction,” he said. “But there’s still more inside.” Each successive application will reach rust that’s deeper in the tile.

If you can’t remove all the rust, or if the rusty tiles are cracked, you may be able to replace just those pieces. Retro-style hexagonal tiles are very popular, so you may be able to find an exact or close match. Get replacements before you take out the old pieces. On a floor with small hexagonal tiles, a rotary tool fitted with a 1/16-inch bit works well. Dremel is the best-known brand for these tools, which are typically sold with a variety of attachments. At Ace Hardware, for example, the price ranges from $44.99 to $129.99, depending on the number of accessories and the tool’s power ratings. Any of the tools should be powerful enough to remove grout around a few tiles. The Dremel Grout Removal Kit, which includes a bit and an attachment that helps hold the tool at the most efficient cutting angle, is $29.99 at Ace Hardware.

Tiny tiles are back in a big way

Once the grout is out, pry up the old tile and coat the back of the replacement piece with tile adhesive. You’ll need only a little, so you might want to buy a squeeze tube, such as the Red Devil Tile Paste Adhesive ($7.13 for a 5.5-ounce tube on Amazon). Press the piece into place. If the adhesive pools up in the gaps around the tile, clean them out with a toothpick or other slender tool, so there’s room for grout. When the adhesive is dry, fill the edges around the tile with grout. Use unsanded grout, assuming the grout lines are less than ⅛ inch wide. You’ll need only a little, so consider buying it in a squeeze tube. Red Devil’s 5.5-ounce Pre-Mixed Tile Grout is $7.18 on Amazon.

If you want a different look for your bathroom, you can consider painting the floor or adding new tile on top of the old. Painting is obviously the easier option, but the paint will cover both the tiles and the grout lines; although you will get a clean, uniform look, it won’t have the color contrast of tile surrounded by grout. You also would lose the vintage look, and you’d be cleaning and inevitably scratching paint, not the far hardier finish of glazed ceramic tile.

Adding a new layer of tile gets around those issues: You would still see the grout, and the floor would perform as if it were installed from scratch. But there are a few caveats. First, adding tile on top of old tile is only a good idea if the floor is stiff and the added weight isn’t an issue. If the underlying floor is concrete, you should be okay. But if you have a wood-framed floor with some bounce to it, be cautious. The new tiles might pop loose.

Also be aware that unless you pay attention to details, you will have a floor that looks like a quick fix, not a quality job. The new layer will change the height of the floor. You will probably need to trim the bottom of the door, so it swings freely. Door trim and baseboards look odd unless the bottom edges overlay the flooring. If there’s one place in a house where people have time to stare at these details, it’s the bathroom. So even though it’s extra effort, you will probably want to cut a little off the bottom edge of the door trim and remove and reinstall the baseboards. If you have a built-in vanity, the higher flooring will cut down on the kick space unless you remove the cabinet, install the tile and reinstall the cabinet. You will definitely need to remove and reinstall the toilet or upgrade to a new one.

If you proceed, you or whomever you hire will need to prep the existing tile by scratching up the surface with 80-grit sandpaper to make it less slick, which will help the new tile stick. And any high spots will need to be ground down. But after that, the installation should proceed as if you were getting a new floor. The most appropriate adhesive and caulk will depend on the tiles you choose.

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What to do about rust