How to regrout a shower — it’s one of the most common questions we get from St. Louis homeowners looking at grout that’s cracked, stained, or growing mold that won’t clean off.
The short answer is that shower regrouting is a multi-step process that takes a full weekend when done correctly. Old grout has to come completely out before new grout goes in. The corners need silicone caulk, not grout. And the new grout needs 48 to 72 hours to cure before the shower can be used again.
When it’s done right, a regrout restores the waterproof barrier behind your tile and gives a shower 10 to 20 more years of life. When it’s rushed or done wrong — new grout over old grout, grouted corners instead of caulked ones, grout applied to a wet substrate — it fails within months. We get calls to fix both scenarios regularly.
This guide covers what the process actually involves, what goes wrong and why, what it costs in St. Louis in 2026, and how to tell whether your shower needs regrouting or something more.
Does Your Shower Actually Need to Be Regrouted?
Not every grout problem requires a full regrout. Before spending money on anything, it’s worth spending five minutes assessing what you’re actually dealing with.
Signs That Point to Regrouting
Cracking or crumbling grout. Press on the grout joints. If they give, flex, or crumble, the grout has failed. Water is already finding its way behind the tile with every shower.
Grout separating from the tile edge. When grout pulls away and leaves a visible gap at the tile edge, that gap is a direct water entry point. You can’t fill over it — the old grout needs to come out first.
Mold that keeps coming back. If mold returns within a week or two of cleaning, it’s established inside the grout, not just on the surface. Surface treatments don’t reach it. The grout needs to come out.
Permanent discoloration. Grout that’s been permanently stained by years of hard water, soap, or mold — even after deep cleaning — is often better replaced than chased with cleaning products.
When You Can Get Away With Cleaning Instead
If the grout is intact and uncracked but just discolored, press on every joint first. If they’re all solid and there’s no give at all, the grout is structurally fine. A proper grout cleaner with a stiff brush, followed by a fresh coat of penetrating sealer, might be all that’s needed.
When the Shower Has Gone Past Regrouting
This is the part most people don’t know to check — and it’s the most important.
Tap test every tile. Knock on each one with a knuckle. A hollow sound means the thinset bond underneath has failed. The tile isn’t actually attached anymore. Regrouting over hollow tiles traps moisture behind them and makes the problem worse — it doesn’t fix it.
Press on the walls. Push gently on the tile surface near the bottom of the walls and in the corners. Any flex or soft feel means the substrate behind the tile is wet and compromised. The problem isn’t the grout — it’s what’s behind it.
Check for cracked tiles. A cracked tile breaks the waterproof surface. Regrouting around it doesn’t restore that barrier.
If you find hollow tiles, soft walls, or cracked tiles across multiple areas, the shower needs more than regrouting. At that point, our shower tile repair assessment is the right starting point. We can tell you in one visit whether the damage is limited to the grout or whether the substrate behind the tile has been compromised — which changes everything about what the right repair is.
Grout vs. Caulk: The Most Common Shower Mistake
Before we talk about the regrouting process, there’s one distinction that determines whether a regrout lasts or fails within a year.
Tile-to-tile joints on flat wall and floor surfaces → grout.
Corners and transitions — where the floor meets the wall, where two walls meet, where tile meets a tub or shower pan edge → silicone caulk. Never grout.
Corners move. Every day, the shower structure expands slightly when it’s warm and contracts when it’s cool. Grout is rigid. At a movement joint, it cracks — usually within a year, sometimes faster. Silicone caulk is flexible. It moves with the structure and stays sealed.
We see grouted corners in almost every shower we’re called to repair. The grout looks fine for a while. Then it cracks, opens up, and water gets behind the tile at the most vulnerable transition point in the whole shower.
If your shower corners currently have grout in them, that’s why they keep cracking. Replacing corner grout with color-matched silicone caulk solves the problem permanently.
What the Regrouting Process Actually Involves
Removing the Old Grout
This is the most time-consuming part of the job — and the part that determines whether everything that follows holds up.
New grout applied over old grout doesn’t bond to the tile or the substrate. It bonds to the old grout, which is already failing. It looks fine initially and falls out within months. The old grout has to be removed to a depth of at least 1/4 inch — enough that the new grout has a clean surface area to bond to on both sides of the joint.
We use oscillating multi-tools with grout removal blades for the field work. Inside corners require grout saws and manual work to avoid chipping tile edges. The process produces significant dust — old grout contains silica, which requires respiratory protection and proper cleanup.
This step takes 3 to 5 hours on a standard shower surround. Rushing it is the fastest way to ensure the new grout fails early.
Inspecting What’s Underneath
Once the grout is out, we can see the tile edges and substrate clearly for the first time. This is when we find out if the regrout is straightforward or if there are problems that need addressing before new grout goes in.
Tile edges that have chipped slightly — not a problem. Backer board that looks dark or wet behind a cleared joint — a problem. Tiles that shift when pressed after the grout is removed — a problem. We assess what we find before any new material goes in.
Cleaning and Drying the Joints
Every joint gets vacuumed and wiped before new grout is applied. Any dust, debris, or moisture left in the joint weakens the bond. We let joints dry completely — typically 2 to 4 hours in a ventilated bathroom — before grouting starts.
Applying New Grout
We use Laticrete grout systems on every project. The type depends on joint width. Shower walls with joints under 1/8 inch get unsanded grout — that’s most standard installations. Shower floors with wider joints get sanded grout. And for clients who want the most durable finish that never needs sealing, epoxy grout is the answer.
Grout goes on with a rubber float, packed firmly into the joint at a 45-degree angle. After a section is packed, the float scrapes across diagonally to remove excess from the tile surface. Walls are worked top-down. The floor works from the back toward the drain.
The mix ratio matters. Too much water makes grout weak — it looks right when it goes on and cracks after it cures. We mix to a thick, workable consistency and let the grout slake for 5 to 10 minutes after initial mixing, which activates the chemistry and improves the final bond.
Cleaning the Haze
About 10 to 15 minutes after application, cleaning starts. A damp sponge — wrung out thoroughly, not wet — wipes diagonally across the tile surface to remove grout from the tile face while leaving the joints full. We rinse frequently and change the water when it goes milky. This process happens in 2 to 3 passes as the grout firms up.
The final thin haze that remains after sponging is buffed off with a dry cloth once the grout has cured.
Tooling the Joints
As the grout firms — usually 30 to 45 minutes after application — we run a finger or jointing tool lightly along each joint to compress and smooth the surface. This makes the grout slightly concave, helps it shed water, and gives it a consistent finished appearance.
Caulking All Corners
Once the grout is cleaned and the tape removed — while the grout is still green — color-matched silicone caulk goes into every corner and transition. A smooth bead, tooled wet with a finger, then tape pulled immediately. No corner gets grout. Every corner gets caulk.
Curing and Sealing
New cement-based grout needs at least 48 to 72 hours before the shower is used. The floor needs 7 days before sustained water exposure — shower floors sit in standing water with every use, and undercured grout soaks up that water before the chemical structure is set.
After curing, we apply a penetrating grout sealer to all cement-based grout. Penetrating sealers soak into the grout and protect from within. Surface sealers sit on top and wear off faster. Epoxy grout needs no sealing.
What Goes Wrong in a Shower Regrout
We get called to repair regrout work regularly. The same mistakes come up every time.
New grout applied over old grout. It looks fine for a few months. Then joints pop out in chunks because the bond was to the failed material, not to the tile.
Grouted corners. Cracks appear within 6 to 18 months. Water gets behind the tile at the most vulnerable points in the shower.
Grout applied to a damp substrate. Looks right when it goes on. Fails early because moisture in the joint prevents proper bonding.
Wrong grout type for the joint width. Sanded grout in a narrow joint cracks under its own tension. Unsanded grout in a wide floor joint shrinks and pulls away from the tile edges.
Shower used before grout cures. The most common homeowner mistake. The grout looks solid. It isn’t. Water exposure before the cure is complete weakens the final bond and is the most common reason new grout fails in the first year.
How Long Does a Shower Regrout Last?
Done correctly, cement-based grout in a shower lasts 10 to 20 years. Epoxy grout lasts 20+ years without sealing.
What shortens it: grouted corners instead of caulked ones, early water exposure, skipping the sealer on cement grout, and hard water deposits left to build up without regular cleaning.
Done wrong — new grout over old, wet substrate, wrong product — it can fail in under a year.
Shower Regrouting Cost in St. Louis (2026)
Professional shower regrouting in St. Louis typically runs $600 to $1,500 for a standard shower. The range reflects shower size, tile complexity, whether the floor is included alongside the walls, and what we find during the assessment.
Labor runs $10 to $25 per square foot. Materials add $1 to $5 per square foot depending on grout type. Epoxy grout costs more in materials but saves the cost of sealing and resealing over time.
We provide free on-site estimates with clear, itemized pricing. No phone-call range that changes when we arrive.
FAQs: How to Regrout a Shower
No — not correctly. New grout applied over old grout bonds to failed material, not to the tile. It looks fine for a few months and then falls out. The old grout needs to come out to at least 1/4 inch depth before new grout is applied.
Unsanded grout for joints under 1/8 inch — most shower walls. Sanded grout for joints 1/8 inch or wider — most shower floors. Epoxy grout works for any joint width, requires no sealing, and is the most durable option available.
Walls: 48 to 72 hours minimum. Floor: 7 days before regular use. Using the shower too soon is the most common reason new grout fails in the first year.
Yes, for cement-based grout — sanded or unsanded. A penetrating sealer should be applied after the 72-hour cure period. Epoxy grout does not require sealing.
Regrouting replaces the cement grout between tiles on flat surfaces. Recaulking replaces the silicone caulk in corners and transitions. A proper shower maintenance job does both — fresh grout in the field, fresh silicone caulk in every corner.
Professional regrouting runs $600 to $1,500 for a standard shower in St. Louis, depending on size, tile type, and scope. We provide free on-site estimates with itemized pricing.
Shower Grout Looking Old in St. Louis?
If your shower grout is cracking, pulling away, or growing mold that won’t clean off — we can tell you in one visit whether regrouting is the right fix or whether there’s something behind the tile that needs to come out first.
At Tile Gurus, every regrout uses Laticrete materials, silicone caulk in every corner, and a penetrating sealer after curing. Landon has been doing this work since he was seven. We know what a regrout that lasts looks like — and we know what a failing one looks like, because we fix them too.
We serve homeowners across St. Louis County and St. Charles County — Chesterfield, Kirkwood, Clayton, Webster Groves, O’Fallon, Creve Coeur, Wentzville, and beyond. For larger problems involving tile failure or substrate damage, see our custom shower tile and shower floor tile services.
📞 Call or text (636) 297-5165 for a free estimate.
