How to Regrout a Shower

The Short Answer

If the Tile Is Solid and the Grout Is Crumbly, Regrouting Works

A regrout takes the old grout out of the joints, cleans the joint down, packs it back with new grout matched to your tile, and seals it once it cures. That is the whole job when the tile is still bonded to a sound wall. When the wall behind the tile has water in it, the same shower needs the wall opened, and the grout is the last thing that gets fixed.

Sorting It Out

How to Tell a Grout Problem From a Wall Problem

You do not need to open anything to sort most of this out. Look at the failure, not at the shower.

When The Joint Wants Silicone

There is one more case that looks like a grout problem and is not. A joint that fails every single time in the same place, usually a corner, the joint where the tub meets the wall, or where the wall meets the floor, is a joint that moves. Those joints want silicone, not grout. Grout cannot flex. If you regrout them, they fail again on the same schedule.

The Work

What a Regrout Actually Involves

1. 1.Clear and protect the room. Door masked off, floor covered, the rest of the house kept out of the dust.
2. 2.Take the old grout out. A grout rake or an oscillating tool with a grout blade pulls it, and a carbide blade on a hand tool works in tight spots. The joint has to come out down to the back of it, not just scraped at the surface.
3. 3.Clean the joint. Vacuum the debris and wipe the tile faces, because new grout bonds to the sides of the tile and a dusty joint is a weak joint.
4. 4.Look at what is under it while the joint is open. This is the moment to see if the backer board is damp, or if the wall moves. If it does, that changes the scope and it gets written down before the work goes on.
5. 5.Mix the grout to the consistency on the bag. Too wet and it goes soft and dusty. Too dry and it does not pack into the joint.
6. 6.Pack the joint at an angle with a float, then strike the face off with the edge of the float so the joint is flat and the tile edges are clean.
7. 7.Wait until the grout will hold a fingerprint without smearing, then sponge it with clean water. A second pass with a fresh sponge takes the haze off.
8. 8.Let it cure, then seal it if it is cement grout. The joint has to be dry before sealer goes on, and sealing over dirty or damp grout locks the stain in for good.
9. 9.Run silicone in the joints that move. Corners, the tub edge, and the wall to floor transition get silicone, not grout.

One note on materials. Epoxy grout does not need sealing, because it is not porous. Cement grout does. We check which one your shower has before anyone buys sealer. We set the tile you buy and we set the grout you buy, and we will tell you what your joint needs before the order goes in.

Tools

What Tools a Regrout Needs

• A grout rake for the open joint, or an oscillating tool with a grout blade. The rake is slower and it is gentler on the tile edge.
• A grout float for packing the joint and a margin trowel for mixing.
• A vacuum, a stiff brush, clean water, and a fresh sponge for every joint you clean.
• A razor scraper for the haze, and tape along the tile face so the cleanup does not scratch the glaze.
• A silicone gun with pure silicone caulk for the corners and the tub joint.
• Eye protection, a dust mask, gloves, and a wet and dry vacuum for the cleanup.

The tools are cheap. The part that decides how a regrout turns out is whether the old grout comes all the way out and whether the joint is clean before the new grout goes in. That is a matter of patience, not of equipment.

Failure

What Makes a Regrout Fail

• Regrouting over a problem that is not the grout. If water is coming through the wall or through the pan, the new grout fails the same way the old one did.
• Grouting a joint that moves. Corners and the tub joint need silicone, and grout in them cracks along the same line every time.
• Leaving old grout in the joint. New grout does not bond to old grout, so a skim over the old joint is a thin new surface sitting on a weak one.
• Mixing the grout too wet. It looks fine going down and it dusts out later, because there was not enough binder in it.
• Sealing too early, or sealing over grout that is dirty or damp. That locks the stain in permanently.
• Packing the joint over a wet or moving substrate. The grout cannot bond to a damp backer board.
• Using the shower before the silicone has cured. A joint that is hit with water too early is a joint that has to be redone.

What to Do Next

What to Do Next

If you are not sure which kind of problem you have, the next step is a short visit where somebody knocks on the tile, looks at the joints, and tells you which of three things it is: a grout job, a silicone job, or a wall that has to be opened. Nothing gets started until you have that in writing.

What Goes On The Estimate

On the estimate we write down what we found, what we are going to do about it, and what changes the price if the wall behind the tile is in worse shape than the surface suggests. If a shower needs more than a regrout, we say so on the estimate instead of after the first day of work.