How to Match Grout Around Replaced Tile

Why this matters

The tile you replaced can be a perfect match and the repair still shows, because the grout around it is a different color. Customers see grout first: it is the grid their eye reads, and a box of bright new grout lines around four tiles is a target painted on the floor. The trap is that grout lies about its color twice. The old grout is darker than it was installed, because it is dirty, and the new grout is darker than it will be, because it is wet. A tech who matches wet new grout to dirty old grout is comparing two wrong numbers, and the result shows up the next morning, a shade too light, after the truck is gone.

The procedure below produces a short written log as it goes. The log is the point: it is what lets you mix the same color tomorrow, and what lets the next tech who opens this wall match your grout instead of guessing.

The steps, and the line each one writes

1. Measure the joint, and let it pick the grout type. Measure the width of the old joints with a ruler or a set of feeler gauges. The common rule, which the grout bag states for that product: unsanded grout for joints narrower than 1/8 in, sanded for 1/8 in and wider, up to the bag's maximum. Reason: unsanded grout in a wide joint shrinks and cracks as it cures, and sanded grout will not pack into a narrow joint and its sand scratches polished stone and glass. Then look at the old grout: glossy, very hard, resisting a scratch from a key, is likely epoxy, which takes epoxy to match. Log line: joint width and the grout type it calls for.

2. Clean a section of the old grout to see its real color. Pick a patch of joints next to the repair, about a hand's width, and scrub it with a neutral or alkaline tile cleaner and a stiff nylon brush, then rinse and let it dry fully. Do not use an acid cleaner. Reason: the grout's color in use is the grout plus whatever soap, oil and soil it has absorbed, and the only stable reference is the grout itself. Acid etches cement grout and attacks marble and other calcareous stone, so it changes the very thing you are trying to read. Hazard: keep cleaners apart, because mixing products can release toxic gas, and ventilate the room; wear gloves and eye protection. Log line: cleaned or not, with what, and how long it dried.

3. Decide whether you match the clean color or the dirty one. This is the honest fork. If the customer will clean the whole floor, match the clean color. If not, the repair will sit beside dirty grout, and you may need to match a shade darker than the clean patch, or clean the whole field around the repair as part of the job. Ask, and write the answer down. Log line: target color, clean or as-found.

4. Test whether the old grout is sealed. Put a few drops of water on a cleaned joint. If it darkens within a few seconds, the grout is unsealed or the seal has worn off. If the water beads and the grout stays dry for a minute or more, it is sealed. Reason: a sealer slightly deepens and can slightly gloss the color, so sealed old grout and unsealed new grout look different even when the powder was the same. Log line: sealed or not.

5. Compare against the chart in daylight. Take the grout maker's color chart, or better, its cured sample sticks where the store has them, to the cleaned patch, and compare by daylight from a window, not under kitchen LEDs or a work light. Pick the two nearest colors, one slightly lighter and one slightly darker, if no single chip is right. Reason: the same grout reads warmer or cooler under different lamps, and a match chosen under one light can miss under another. Log line: the candidate colors and the light you judged them in.

6. Make test batches, and let them dry before you judge. Mix small batches, one straight color and one or two blends of the two candidates by volume, blending the dry powders completely before adding water. Measure the water with a marked cup and use the same proportion every time. Press each into a scrap: a joint between two offcut tiles taped to a board is ideal, because grout in a real joint reads differently from a smear on cardboard. Let them dry at least overnight before comparing. Reason: wet grout reads darker than dry grout, and it lightens as it cures. Extra water also lightens it and makes it blotchy, which is why the water is measured. Hazard: dry grout powder, especially sanded, carries crystalline silica; pour it low and slowly into the water rather than dumping it, and keep your face out of the dust. Log line: each batch, its ratio, its water, wet read and dry read.

7. Mix the chosen batch the same way, and grout. Same ratio, same water, same mixing time. Pack the joints fully, strike them to the same depth and profile as the old joints, and clean the tile faces with a damp sponge, wrung out, since a soaking sponge pulls color out of the joint. Log line: the batch used.

8. Seal if the old was sealed. After the cure the sealer label states, apply the same kind of penetrating sealer to the new joints, and lightly to the cleaned old patch so it reads the same. If the old was not sealed, sealing only the new joints makes them read different from everything else. Log line: sealer and date, or "not sealed, matched old".

Worked example: the match log for a shower valve

A plumber replaced a shower valve from the front and had to remove six 4 1/4 in wall tiles around the trim plate. The tiles were reset with attic stock the homeowner had kept. The grout is about 20 years old, installed as off-white and now reading beige. The filled-in log:

 GROUT MATCH LOG - hall bath, shower valve
 ------------------------------------------------
 Joint width:   1/16 in, measured -> unsanded
 Old grout:     cement; scratches with key, not epoxy
 Cleaned:       6 in patch, alkaline cleaner,
                dried 2 h before reading
 Target:        clean color (customer will clean
                whole shower this weekend)
 Sealed?:       water darkened in about 3 s -> no
 Light:         daylight, window, early afternoon
 Candidates:    A = bright white  B = warm bone
 ------------------------------------------------
 Batch  Mix (by vol)  Water        Wet     Dry 24 h
 1      B straight    marked line  match   too light
 2      3 B : 1 A     marked line  lighter too light
 3      B, then 1/4   marked line  darker  close,
        part tint                          slightly cool
 ------------------------------------------------
 Result: no batch matched within 24 h. B straight
 matched wet, dried lighter.
 Next: order cured sample sticks, two darker
 colors, before grouting.

The log records a miss. Batch 1 looked like a perfect match wet and dried noticeably lighter than the cleaned old grout overnight, which is exactly the trap in step 6. Batch 2 went the wrong way, because adding the white candidate made a lighter mix out of a base that was already drying too light. Batch 3 used a tint the plumber had on the truck and dried close but cool. Rather than grout with a near miss, the plumber left the joints open with a protective tape over them and the shower out of use, which the customer agreed to in writing for two days, and came back with two darker candidates.

On the return, a darker bone color dried to a match against the cleaned patch in daylight, and the log got one more line: batch 4, the new color straight, at the same water line, dry read "match", used. The old grout was unsealed and stayed unsealed, so the new grout was not sealed either.

The first try was not wasted. It ruled out the obvious color, it caught a match that would have dried wrong, and it gives the next tech the exact color and water that worked.

Two ways a good match goes wrong after you leave

A white haze on dark grout. Dark and colored cement grouts can dry with a chalky white bloom on the surface, called efflorescence, when salts carried by excess water come out as it evaporates. The joint now reads lighter than the batch you matched, and the customer sees a mismatch the next week that was not there when you left. The cause is almost always too much water, in the mix or in the sponge. Measured water in step 6 and a wrung-out sponge in step 7 prevent most of it; a dry haze can often be removed with the cleaner the grout maker names, once the grout has cured.

Matching on a wall and grouting a floor. Floor grout darkens faster than wall grout because it takes foot traffic and mop water. A floor color matched to a cleaned patch will read light against the rest of the floor within a week if the customer does not clean the floor. That is why step 3 asks the question in writing.

When no mix will match

Some old grout has aged unevenly, darker at the floor and lighter up high, or has been half-cleaned for years, and no single new color matches all of it. Three honest options, each a different promise:

• Blend and accept. Grout with the closest color and tell the customer it will read slightly different up close. This is the acceptable grade of repair, and it goes on the estimate before the job, not on the invoice after.
• Color-seal the whole field. A grout colorant, a pigmented sealer brushed onto every joint in the wall or floor, makes all the grout one color, new and old. It is a full-surface job, not a patch, and it is priced that way.
• Regrout the field. Removing and replacing the grout in the whole wall is the only way to get a true uniform result, and it is a tile setter's job. See related: When a Finish Repair Belongs to a Painter or Finish Carpenter.

Which of those the customer bought is the decision; see related: Invisible, Blended or Acceptable: The Three Grades of Finish Repair.

References

• See related: Tile + Grout Selection Reference
• See related: How to Replace a Few Cracked Ceramic Tiles
• See related: Why New Material Does Not Match Old Material
• Grout and sealer manufacturer product data (joint width range, water ratio, cure time before sealing)