Regrout Shower Tile: Step-by-Step DIY Guide

Most homeowners who end up regrouting their shower put it off for way too long. Not because they’re lazy. Because they look at that cracked, moldy grout and genuinely don’t know if they’re looking at a $15 fix or a $1,500 tile replacement job. Here’s what I tell people when they describe it to me: if your tile is solid and your grout is just ugly or deteriorating, you can almost certainly handle this yourself for under $60 in materials and a weekend afternoon.

I’ve regrouted more showers than I can count, both professionally and on my own houses. The work itself isn’t complicated. The part people get wrong is preparation, specifically not removing enough of the old grout before they start applying new product over the top of it. I’ve watched that mistake turn a $60 project into a $400 do-over. This article is going to walk you through doing it right the first time.

One thing worth knowing upfront: not all grout failure looks the same, and the cause matters. Cracked grout in a straight line usually means substrate movement or a crack in the mortar bed underneath. Grout that’s just soft, powdery, or stained is normal wear. If you see cracks running through the tile itself, or if tiles feel hollow when you tap them (that dull thud versus a solid ring), stop and call a tile contractor. But if your tile is tight and the problem is just the grout, you’re in good shape.

What You’re Actually Dealing With

Grout is porous. Even sealed, it absorbs water vapor over years of daily showers, and eventually it breaks down. Most residential shower grout that sees regular use starts showing real wear somewhere between 8 and 15 years, though I’ve seen cheap sanded grout on a busy household shower look rough at 5. The good news is that regrouting doesn’t require removing tile. You’re pulling out the old grout to a sufficient depth and pressing in fresh material.

Here’s the part I wish someone had told me 20 years ago: you don’t need to remove every trace of old grout. You need to remove enough that the new grout has depth to bond and won’t just pop out. The rule of thumb is 2mm minimum. In a typical 3/16" joint, that’s roughly two-thirds of the depth. A lot of DIY guides skip that number entirely, which is why so many regrouting jobs look good for three months and then start crumbling again.

You’re also going to need to decide whether to use sanded or unsanded grout. The dividing line is joint width. For anything under 1/8" (common with small mosaic tile), use unsanded. For wider joints (most standard 4x4 or subway tile installations), use sanded. Using unsanded in a wide joint gives you grout that shrinks as it cures and cracks. Using sanded in a narrow joint scratches polished or glass tile surfaces. The grout bag at the store will tell you the right range, but the manufacturer’s spec sheet, not the bag front, has the real detail.

Tools and Materials

You don’t need much, but what you use matters.

The single most important tool is a grout saw or oscillating multi-tool with a grout removal blade. For a small shower, a $12 manual grout saw from Home Depot works fine, though it’s tedious. For anything larger than about 25 square feet of joints, rent or buy an oscillating tool. Fein makes excellent blades (around $18 for a 2-pack), and the Dremel MM50 oscillating kit runs about $79 at big box stores and makes the removal stage dramatically faster. The first time I tried to do a full shower surround by hand, it took me four hours just on removal. With an oscillating tool, same job: under 90 minutes.

Total for a typical full shower surround: $45-$80 if you already have an oscillating tool, or $80-$160 if you’re buying or renting one.

One product opinion worth stating directly: Mapei Ultracolor Plus FA is genuinely excellent grout. It’s a fast-setting, polymer-modified sanded grout that resists staining better than standard portland-based grouts right out of the bag. Costs maybe $3 more per bag. Worth every cent for a shower application. I’ve been recommending it to homeowners since it became widely available, and as of July 2026, it’s stocked at most Lowes and Home Depot locations.

The Removal Stage (Don’t Rush This)

Vacuum the shower first. Then get a bright work light and look at every grout joint before you start. Mark any joints where the tile looks cracked or sounds hollow when tapped. You want to flag those for closer inspection, not just grout over them.

With your oscillating tool and a carbide grout blade, run along the center of each joint. Keep the tool moving. If you hold it still, you’ll nick the tile edge. The goal is to cut down to 2-3mm depth, not to excavate to the substrate. You’ll hear and feel the difference between cutting grout and hitting tile. After a few joints, you’ll get a feel for the pressure needed.

After removal, vacuum everything, then wipe joints with a damp sponge and let it dry for 30 minutes. Here’s the detail most guides leave out: after vacuuming, blow compressed air across the joints if you have a can or compressor. Grout dust in the joint bottoms interferes with adhesion more than most people expect. I learned that one from a tile setter I worked with in 2011 who had been in the trade for 30 years, and he was right.

Mixing and Applying New Grout

This is where patience matters more than technique.

Mix your grout to the consistency of peanut butter, not hummus. Too wet, and it shrinks and cracks. Most bags tell you to add water to powder, not the other way around. Start with less water than you think you need. If you’re using Mapei Ultracolor Plus FA, the working time is roughly 20-30 minutes before it starts to set, so mix only what you can apply in that window. For a full shower, that means working in sections.

Pack the grout into joints using your rubber float held at roughly 45 degrees, pressing firmly across the joint at an angle (not along it). This forces grout down into the joint rather than dragging it back out. Work a 4-6 square foot section at a time. Apply grout, then come back with your float held nearly flat to scrape the excess off the tile face.

Wait. This is the step homeowners get impatient with. Let the grout haze slightly, usually 10-20 minutes depending on temperature and humidity. Then use a damp (not wet) sponge to clean the tile face in circular motions. Wring the sponge frequently. Change your rinse water often. A contractor I know jokes that if you’re not changing the bucket every 10 minutes, you’re just spreading grout slurry around. He’s not wrong.

A worked example from a job I oversaw: a 42-square-foot tiled shower surround with 4x4 tiles on 3/16" joints. Removal stage took 2.5 hours with an oscillating tool. Mixing and application took 90 minutes working in 5-square-foot sections. Cleanup and sponging took another 45 minutes. Total active time: about 5 hours. Final haze buff with a dry cloth the next morning took 15 minutes.

Corners Get Caulk, Not Grout

This deserves its own section because it’s one of the most common and expensive mistakes I see.

Every inside corner joint in your shower, the corners where two walls meet, where the wall meets the floor, where tile meets the tub deck or shower pan, needs flexible caulk, not grout. Always. The reason is simple physics: those surfaces move independently as the building expands and contracts with temperature and humidity changes. Grout is rigid and will crack in those joints every single time, often within a year. When it cracks, water gets behind the tile.

Use a silicone caulk that’s color-matched to your new grout. Laticrete Latasil and Custom Building Products Polyblend Plus both make color-matched lines. Apply it with steady pressure, smooth it with a wet finger, and don’t shower until it’s cured per the manufacturer’s spec, usually 24 hours minimum but often 48.

I’ll be honest: I skipped the caulk step on my first personal shower regrouting job in 2007 because it seemed fussy. Had a cracked corner joint within eight months. Retapped the tile, checked the substrate, everything was fine. Just the missing caulk. That lesson cost me an afternoon and it stuck.

Sealing and Cure Time

Cement-based grout (which is what almost everyone is using) is porous and needs to be sealed after it cures. The cure time before sealing is typically 72 hours for most sanded grouts, though some fast-setting formulations allow it sooner. Check your specific product.

Aqua Mix Sealer’s Choice Gold is a penetrating sealer that soaks into the grout rather than forming a surface film. Apply it with a small foam brush or applicator bottle directly to the grout joints, let it sit for 5 minutes, and wipe the excess off the tile. You’ll usually want two coats. It’s not expensive (around $16 for a pint), and it genuinely makes the grout easier to clean for years afterward.

One thing I don’t have perfect data on: how often you need to reseal. I’ve seen recommendations ranging from annually to every 3-5 years. My honest take is that it depends heavily on shower traffic and cleaning products used. A single-person household using mild cleaners might go 3-4 years. A family with daily heavy use might want to reseal every 12-18 months. The water bead test tells you: drip water on the grout, and if it soaks in rather than beading, it’s time.

Sources

• Tile Council of North America (TCNA) Handbook for Ceramic, Glass, and Stone Tile Installation: Industry standard reference for grout joint sizing, product selection, and waterproofing requirements.
• Laticrete International Technical Data Sheets: Manufacturer specifications for grout working times, cure schedules, and substrate compatibility.
• Mapei Technical Support Documentation: Product-specific guidance for Ultracolor Plus FA including mix ratios, working time, and sealing recommendations.
• Portland Cement Association (PCA): Technical data on cement-based grout chemistry, water-cement ratios, and shrinkage behavior.
• Custom Building Products Application Guides: Installation standards for caulk versus grout joint placement, particularly for corner and perimeter applications.

Photo: Curtis Adams via Pexels