How to Regrout a Tiled Wall or Floor

Merged job: this walkthrough integrates three queue rows into one — *remove failed grout from a shower* and *regrout a tiled wall or floor* (tile-cutting-and-grout line) plus *rake out failed grout* (demolition-and-opening line) — because they are one job done with two families of tool. If your tile is coming up, you are on the wrong page (see the last section). Written for the person doing the job.

Job: cut the failed grout out of a sound tiled wall or floor and pack the joints with fresh grout — every tile stays put; only the filler is renewed.

Time: removal dominates, by a wide margin. A tub surround or a small backsplash is a morning; a full shower or a bathroom floor is a hard day, and cutting the old grout out is the long half — the fill goes fast and the *cure* runs on the calendar (days before you can seal or shower).

Difficulty: patience and restraint, not strength. Two disciplines decide the whole job: rake to real depth without ever touching the glaze, and don't wash the haze too early.

What this store does NOT sell for this job — stated plainly, because credibility is the moat: the standard fill tool for a normal glazed-tile field is a rubber grout float and a grout sponge, and neither is in this catalog. Buy them anywhere. The 18400 grout bag we *do* sell is the right tool for deep, wide, or porous stone joints — not for floating a standard glazed field. Also not here: the powered grout remover itself (the Regrout Tool), the grout (the chemistry), and a wet saw.

Everything else: the bag or box of grout — sanded or unsanded, and Step 3 decides which · a rubber grout float · a grout sponge and two buckets of clean water · a utility knife for the perimeter caulk · a rented oscillating multi-tool with a grout-removal blade if the floor is big · a HEPA shop vacuum · an N95-or-better respirator · nitrile gloves and safety glasses · a grout-haze cloth (cheesecloth or microfiber) · tub-and-shower caulk for the perimeter and corners · penetrating grout sealer for the finish.

Before you start: is this a regrout at all?

Triage — regrout or full redo. Regrouting fixes *failed filler* on a *sound field*, and nothing else. Tap the tiles with a knuckle and press on them: solid, well-bonded tile with cracked, powdery, stained, or moldy joints → regrout, and you're on the right page. But tiles that sound hollow and drum, tiles that rock or lift, a field that flexes underfoot, or cracks that run *through* the tiles and continue tile-to-tile in a straight line across several of them → that is a setting failure — the bed, the substrate, or building movement — and no grout on earth fixes it. Grout is not glue and not structure; regrouting a moving floor just re-cracks the fresh joints on the same schedule. That job is a tear-out (sister guide *Demolish ceramic tile and thinset*), or a single-tile rescue (*Replace a single cracked tile*) if the failure is one isolated casualty. Say the distinction out loud before you start: demolition takes the tile off; regrouting keeps every tile and renews only what's between them.

Grout, or caulk? Sort the joints before you cut anything. Not every line in a tiled room is a grout joint. The perimeter — tile-to-tub, tile-to-floor, tile-to-countertop — plus every inside corner and every change of plane are movement joints, and they belong to flexible caulk, not grout. Grout packed into a corner between two planes that move independently cracks on a schedule you can set your watch by; it is the single most common reason a "regrout" fails within a month. So divide the work now: field joints (tile-to-tile) get grout — this guide; the perimeter and every corner get raked out and re-caulked (*Remove old caulk* → *Recaulk a bathtub or shower joint*). Plan to do both in one session — the field cures while the caulk sets.

Match the new grout to the joint you have — sanded vs unsanded. Measure the joint width, because it chooses the grout. The trade boundary: unsanded grout for joints narrower than 1/8" (sand grains bridge and void in a hairline joint), sanded at 1/8" and wider (there the sand is structural, controlling shrinkage as the cement cures — a wide joint in unsanded grout cracks down its own centerline). On color: a full-field regrout is your chance to change it, but a *partial* regrout — refilling only the visibly failed joints — prints a color seam where new meets old that never blends. If you can't do the whole field, at least regrout complete runs wall-to-wall, never isolated patches in the middle of a field.

The mold check, and the boundary it draws. Wet-area grout fails wet, and black staining that has gone from *on* the grout to *in* it does not bleach away for good — that's a reason to remove it, not scrub it. Where you're prepping the substrate or keeping any old grout, kill live mold first: a 1:10 bleach solution or an EPA-registered mildewcide, rinsed with clean water, with the room ventilated. And the boundary that is load-bearing, inherited from the recaulk trade: never mix bleach with ammonia- or acid-based cleaners — the reaction makes chloramine or chlorine gas, and a closed shower stall is exactly the small, poorly ventilated box where it accumulates. One honest limit: if the mold runs *behind* the tile — shadows spreading from under the field, a musty wall, soft substrate — grout is cosmetics; that wall is a tear-out, not a regrout.

Rake out the old grout (the long half of the job)

Pick your remover by the joint's state and the job's size. These three tools are not redundant — each owns a different case:

Already crumbling, powdering, or soft joints — and the perimeter caulk → the 43670 Dig-it. Its ground point digs into the failed line and hooks the dead grout up out of the channel; the beveled edge shears the residue off the tile faces, cutting on push and on pull; and the *same* tool then strips the perimeter caulk bead you're replacing (point under the bead, roll it up in a rope; bevel cleans the tracks off both faces). One tool for the crumbly grout, the corners, and the caulk. Its blade is carbon steel — the store's stainless neighbors resist rust, this one earns a wipe-dry and a light film of oil after wet work.

Sound-but-cracked cement grout that has to be *cut* out to depth → the 19402 grout saw. Its abrasive blade grinds a kerf straight down a hard joint where the Dig-it's point would only skate. This is the from-zero tool, and for most whole-field regrouts it is the primary remover.

Whole floors, whole showers — where footage is the enemy → a powered remover. The rental-counter answer is an oscillating multi-tool with a grout-removal blade. If you already own that tool and it has started skating out of joints, worn-smooth tips are exactly the fault and fresh ones are the fix.

The removal doctrine — two-thirds depth, centered, off the glaze. This is the same doctrine whichever tool you're driving:

Cut to about two-thirds of the joint's depth. Enough to give the new grout genuine cross-section and fresh, raw walls to key into — without chasing every last crumb at the bottom. This is why "just grout over the old grout" always fails: a skim over a full joint has no body (it cracks and sheds in months) and no key (old, dense, sealer-saturated grout gives fresh cement nothing to grip). Removal *is* the trade.

Keep the cut centered, and treat the glaze arris on each side as the most visible millimeter in the room. A blade or point that rides against the glaze leaves a chipped, nibbled edge that reads as damage forever. Grout regrows; arrises don't.

Technique: start mid-joint, where the grout stands proudest and the tool has material to seat in — not at an intersection, where four glaze corners crowd the tool and there's nothing to steer by. Short, light strokes; let the grit or the point do the arithmetic, because pressure doesn't cut faster, it just wanders the tool into a tile edge. Open the joint's centerline first, then ease its shoulders. Work intersections last, arriving into each crossing from a groove you already cut so the tool is always supported. On walls, mind the ends of your strokes — a loaded tool skating downhill out of a vertical joint is where most glaze chips happen.

Swap blades on the tells, not the calendar. When the pace halves, when your hand is bearing down harder than you told it to, when the blade starts climbing toward an arris — that is a spent 19403 blade, and a fresh one is arris insurance. Pressing a dead blade harder is the exact mechanism that chips glaze. (Don't confuse the 19403 grout-saw blade with the 19453 hammer-scraper blade one line over — different parent, different trade, zero interchange.)

Epoxy grout is the honesty case. It's a thermoset resin — glassy, uniform, slightly plastic to a fingernail where cement reads matte and chalky — and it barely hand-rakes at all. If the joint is epoxy, the hand tools lose from the start; that removal is oscillating-tool and grinding work. Probe an unknown joint before you commit the afternoon.

Silica — the load-bearing safety of the removal, not boilerplate. Cured cement grout is a crystalline-silica product (sanded grout is substantially silica sand by weight), and cutting or raking it dry throws respirable crystalline silica — the dust behind silicosis and lung cancer, dose-driven, latent, and incurable. Scale the concern honestly: a hand saw in short strokes is the low-energy end; a whole room's worth of joints is real cumulative dust, made at arm's length from your face in a small unventilated room; a powered remover is the peak. So do all of it — mist the joint or work damp where the tool tolerates it, vacuum cuttings as you go with a HEPA vac instead of sweeping dry, ventilate the room, and wear a respirator (N95 as the floor; a half-mask with P100 filters for a full room). OSHA's construction standard, 29 CFR 1926.1153, sets the permissible exposure limit at 50 µg/m³ over 8 hours with an action level at half that, and its general-industry twin is 29 CFR 1910.1053; anyone doing this for pay works under the standard, and a homeowner's lungs get no exemption from the toxicology. (The line's dedicated *Control silica dust in tile and grout work* guide is the fuller treatment.)

Vacuum and wipe the joints clean. Dust or debris left in a joint is a bond-breaker — new grout keys to raw grout walls, not to powder. HEPA-vac every joint, then wipe the field with a damp sponge and let it flash off. When you're done the joints should be clean, sound-walled, and — for cement grout — *slightly damp but not wet* when the new grout goes in. Pull the perimeter caulk and any exposed spacers now; the corners get caulk later, never grout.

Mix the grout

Small batches, and the same water every time — this is where color is won or lost. Buy the grout the joint width chose in Step 3, and mix to the label's ratio. Then the discipline that prevents half the failures on this page: use the identical water-to-powder ratio for every batch. Grout color is water-sensitive — a wetter batch cures lighter, a drier batch darker — so eyeballed water prints a patchwork of shades across a floor that looked uniform while wet. Measure the water; don't pour by feel. Mix to a stiff, peanut-butter-thick paste that holds a ridge: too wet and you get shrinkage, efflorescence, weak joints, and washed-out color; too dry and it won't pack or bond. Let the batch slake (rest) the few minutes the bag specifies, then remix — slaking lets the cement and pigment wet out fully, and skipping it leaves the batch weaker and blotchier. Wear gloves: wet cement grout is caustic (it runs pH 12–13) and burns skin on long contact without much warning. Mix only what you can pack and tool before it starts to set — a stiffening batch is a fight the grout wins.

Float it in

Pack it diagonally, at 45°, to full depth. Load the rubber float, hold it at about 45° to the tile face, and press the grout diagonally across the joints — never along them. Diagonal strokes let the float ride *across* each joint and drive grout in, while stroking *along* a joint lets the float's edge dip into the channel and scoop the grout right back out. Work the grout from several directions so every joint packs full depth with no trapped air — pinholed, weak, hollow joints come from under-packing, and a joint that is full and dense is the entire structural point of regrouting (you removed to two-thirds depth precisely so the new grout would have real body). Press firmly and make the *grout*, not the float, do the filling.

Strike off the excess — float on edge, diagonal again. Once a manageable section is packed, tip the float up nearly on edge, like a squeegee, and sweep it diagonally across the tiles to shear off the surplus and leave the joints full and flush. Diagonal again, so the edge skims the tile and doesn't dig the joints back out. Now the tile face carries only a thin film — and that film is what the sponge takes off next, on a timer. Work in sections small enough that you can pack, strike, and later sponge each one inside the grout's working window; don't grout more floor than you can tool.

Tool and strike, then the timed sponge-wash

Wait for the initial set — this is the haze window, and it decides everything. Stop and wait. The grout has to firm up before water touches it, or the sponge drags it straight back out. The test is a thumbprint: press a joint, and when it's firm enough to take a print without paste lifting onto your thumb, the first sponge pass is due. Washing too early is the single most common regrout mistake — see Step 13.

The first sponge pass — damp, not wet — tools the joint *and* starts the haze clock. Wring the grout sponge out in clean water until it is barely damp; a dripping sponge is how you ruin a floor. Wipe the tile face in light strokes, rinsing the sponge and wringing it near-dry every pass or two, and change the water the moment it turns milky. The damp sponge does two jobs at once: a light drag along each joint after the cross-strokes shapes it to a consistent, slightly concave profile, and the face of the sponge lifts the surface film off the tile. The discipline that decides the result:

Barely damp, light pressure. Too much water pulls cement and pigment out of the joints — that is low, pitted joints, blotchy color, and efflorescence later.

Don't overwork it. Two or three light passes with clean water beat ten wet scrubs; every extra wet pass thins the joint and washes color out of it.

Rinse and change water constantly. A dirty sponge just smears grout slurry into a haze you'll fight for an hour.

Buff the haze — inside its window. As the last film dries it leaves a light cementitious haze on the tile face. There is a window: after the grout has set hard enough that buffing won't disturb the joints, but before the haze cements itself onto the tile — usually not long after the sponge passes, once the surface goes matte. Buff it off with a dry cheesecloth or microfiber cloth. The trap this step exists to prevent: if you go back and *wash* the early haze with a wet sponge, you re-wet the joints, drag grout, and smear a worse haze. Dry-buff the fresh haze; save water for genuinely set grout. A haze that has hardened past the window needs a proper grout-haze remover (a mild acid), later and per its own label — never splashed onto fresh, unsealed grout you'll etch.

Cure, then re-caulk and seal

Cure it slow and damp. Fresh cement grout gains strength by *curing*, not merely drying, and it cures stronger slightly damp than bone-dry — a light mist and a cover for the first day or two make a denser, harder, less-efflorescent joint, where a joint that flash-dries in a hot room ends up weak and powdery. Keep traffic off a floor and water off a shower for the label's cure time — days, not hours. No showering, no cleaning products, no scrubbing the new joints while they cure.

Re-caulk the movement joints while the field cures. Now the perimeter and corners you raked out in Step 2 get their flexible bead — tile-to-tub, inside corners, plane changes — with tub-and-shower caulk, tooled once, and the tub filled first if it's a bathtub joint. This is not optional and it is not grout: a grouted corner cracks, a caulked one flexes. The *Recaulk a bathtub or shower joint* guide owns the whole method (and the fill-the-tub physics behind it).

Seal the grout after full cure. Cement grout is porous — it drinks water and stains, and in a wet area an unsealed joint is a mold reservoir waiting to happen. After the grout has fully cured (the days the bag specifies — sealing too early traps moisture and fails), work a penetrating grout sealer into the joints, wipe the excess off the tile face before it dries, and give it the recoat and dry time the sealer's label states. Wet-area grout is a wear layer — re-seal it periodically. (Epoxy grout, if that's what you used, is non-porous by chemistry and needs no sealing — but epoxy is a different install, with a short pot life and its own rules.)

What goes wrong (and the fix)

"I chipped the glaze raking the grout." Aggressive removal — a spent blade or a loaded point pressed harder and allowed to climb out of the channel into the arris. Center the cut, take short light strokes, swap to a fresh 19403 blade on the tells, and open the joint's centerline before its shoulders. The chip is permanent; the discipline that prevents it is free.

"The new joints are pinholed, weak, or hollow." Under-packing — the grout wasn't pressed to full depth from enough directions, or the batch was too wet (it shrank) or too dry (it wouldn't consolidate). Rake the weak joint back out and repack it firmly on the diagonal, full depth. That two-thirds-depth removal exists precisely to give the fill room to be strong.

"There's a haze I can't get off." You washed too early and smeared grout slurry, or you let the haze harden past its window. Fresh smear: let it set, then dry-buff with cheesecloth. Hardened haze: a grout-haze remover per its label, after the grout has cured — and don't drown it in water, which restarts the color-wash problem.

"The color came out blotchy and patchy." Inconsistent water — batch-to-batch mix ratios, or over-wet sponging pulling pigment out. Measure the water identically every batch, slake every batch, and sponge barely damp. A badly blotched floor sometimes only recovers with a grout colorant over the top — far cheaper to mix consistently the first time.

"A white powder keeps blooming on the joints." Efflorescence — soluble salts carried to the surface by too much water, whether a wet mix, wet sponging, or water migrating through the joint from behind. Let it fully cure and dry, brush off the dry bloom (an efflorescence cleaner if it's stubborn), and next time mix drier and sponge with less water. Persistent efflorescence in a shower means water is getting behind the tile — a bigger problem than the grout.

"It cracked again in the same corners within weeks." Those aren't grout joints — they're movement joints, and grout can't flex. Rake the cracked corner out and *caulk* it (Step 16). This is the most common "my regrout failed" story, and it's a tool-choice error, not a technique error.

"The whole field is re-cracking / tiles sound hollow underneath." Not a grout problem — the tile or the bed is moving, and regrout was the wrong repair. You're in tear-out or single-tile-replacement territory (sister guides). An honest guide says when the job isn't the job.

The history footnote (because these pages should be worth reading)

Grout failure is a young household chore because the grout joint itself is young. For most of the history of tile the setting method was the full mortar bed — an inch or more of floated sand-cement with the tile beaten into it — and there were no thin cement lines to fail; the joints were simply part of the bed.

Cross-linked guides: *Remove failed grout from a shower* and *Control silica dust in tile and grout work* (same line) · *Choose a grout joint width* (sanded vs unsanded) · *Replace a single cracked tile* (when a tile, not just the joint, has failed) · *Remove old caulk* → *Recaulk a bathtub or shower joint* (the movement joints this guide hands off) · *Dig out crumbling mortar joints* and *Strip an old caulk bead* (the Dig-it's sister jobs) · and the clear opposite of this job, *Demolish ceramic tile and thinset* (when the tile comes off instead of staying). Every linked PDP lists this guide under its applications — the graph runs both directions.