Bathroom Tile Regrouting DIY: 6 Steps to Stop Water Damage

TL;DR: Cracked or missing grout allows water to seep behind tiles and into walls, causing mold and structural damage. Remove old grout with a grout saw, vacuum all dust from joints, apply new grout diagonally across tiles to pack the joints, then seal after 72 hours. The project costs $25-40 and takes 4-6 hours for a standard tub surround.

_Last reviewed: July 2026 · 6 min read_

Cracked grout around your tub or shower isn't just cosmetic—every time you run the water, moisture works its way into the wall cavity. Over a year, that can mean 2-5 gallons of water behind the tile, rotting studs and growing mold. The fix is regrouting, and you can do it yourself in a weekend with basic tools and $30 in materials.

Okoniq Property Hub logs every bathroom repair with photos and dates so you know when you last regrouted and when the next round is due.

Why does cracked or missing grout matter?

Grout seals the joints between tiles. When it cracks or falls out, water flows through the gap and sits against the drywall or backer board behind the tile. In a shower that gets daily use, a 1-inch crack can channel a tablespoon of water per shower—350 tablespoons a year, or about 1.3 gallons. Multiply that by a dozen cracks and you're pumping gallons into the wall. The result: soft drywall, black mold, and eventual tile failure when the adhesive breaks down. Regrouting stops the leak before you need a $4,000 tile replacement. If moisture is already an issue elsewhere in the bathroom, a bathroom exhaust fan upgrade helps pull humidity out of the air before it condenses on tile.

How do you remove old grout?

You need clean tile edges for the new grout to bond. A grout saw—a small hand tool with a carbide or diamond grit blade—cuts out the old material without scratching the tile face. Hold the saw at a shallow angle and make two passes down each joint to a depth of 1/8 to 1/4 inch. Don't try to remove all the grout down to the backer board; you only need to create a clean channel for the new material. An oscillating multi-tool with a grout blade speeds the job but costs $80-120 if you don't already own one. For a single bathroom, the $8 hand saw is enough. Wear safety glasses—grout dust flies. This step takes 60-90 minutes for a typical tub surround.

Why vacuum the joints before you apply new grout?

New grout won't adhere to dusty tile edges. After you finish cutting, use a shop vacuum with a crevice nozzle to pull all dust and loose grout crumbs from the joints. Then wipe the tile faces with a damp sponge—don't flood the joints, just remove the surface film. Let the tile dry for 10 minutes. If you skip this step, the new grout sits on a layer of powder and pulls away from the tile within six months. This vacuuming and wipe-down adds 15 minutes but doubles the life of the repair. If you're dealing with persistent moisture problems in adjacent spaces, basement waterproofing and crawl space moisture control may be worth checking to address the root cause.

How do you mix and apply new grout?

Buy unsanded grout for joints narrower than 1/8 inch (most wall tile), sanded grout for wider joints (floor tile). Mix the powder with water in a small bucket according to package directions—about the consistency of peanut butter. Let it slake (rest) for 10 minutes, then stir again without adding more water. Load a rubber grout float and apply the grout diagonally across the tile face, pressing into the joints with firm strokes at a 45-degree angle. Diagonal strokes pack the joints without pulling grout back out. Make two passes over each joint to ensure no voids. After you've covered a 10-square-foot section, hold the float at a near-vertical angle and scrape diagonally across the tile to remove excess grout from the surface. Wait 10-15 minutes until the grout is firm to the touch, then wipe the tile with a damp sponge in a circular motion to clean the haze. Rinse the sponge frequently. For corners and edges where the float doesn't fit, use a gloved finger to press grout into the joint.

When and how do you seal the grout?

Sealant blocks water and stains from soaking in. Wait 72 hours after grouting for the material to cure fully—check the package for the exact time, as some rapid-set formulas cure in 24 hours. Buy a penetrating silicone or siloxane sealer (not a topical coating) and apply it with a small foam brush or sponge applicator. Work in 3-foot sections, brushing the sealer onto the grout lines and wiping any overspray off the tile face within a minute. One coat is standard; two coats 30 minutes apart add extra protection in high-traffic showers. Reapply sealer every 12-18 months. Mark the date in your maintenance log so you don't forget. If you're tracking multiple bathrooms across rental properties, Okoniq Property Hub stores the sealing schedule with photos of each job.

What tools and materials do you need?

For a standard tub surround (roughly 60 square feet of tile), expect to spend $25-40 and 4-6 hours:

• Grout saw or oscillating tool with grout blade: $8-120
• Shop vacuum: $40 if you don't own one
• 10-pound bag of grout (sanded or unsanded): $10-15
• Rubber grout float: $8
• Grout sponge (large, with rounded corners): $3
• Grout sealer (quart bottle): $12-18
• Bucket, gloves, safety glasses: under $10 total

If you're also replacing caulk around the tub edge, add a caulk gun and a tube of mold-resistant silicone caulk ($6). Pull the old caulk with a utility knife before you start grouting, then apply fresh caulk after the grout has cured. Caulk is flexible and belongs in corners and along the tub rim; grout is rigid and belongs in tile-to-tile joints. Mixing the two causes cracking. For other small repairs that add up—like a door hinge maintenance fix or ceiling light fixture replacement—keeping a log helps you see patterns and plan your next project.

FAQ

How long does DIY regrouting last?

Properly applied and sealed grout lasts 10-15 years in a residential shower. High-traffic showers or soft water areas may see 8-10 years. Reseal every 12-18 months to extend the life.

Can you grout over old grout?

Only if the existing grout is sound and you're filling hairline cracks. If the old grout is crumbling or missing in chunks, you must remove it to a clean edge or the new layer will delaminate within months.

What's the difference between sanded and unsanded grout?

Sanded grout contains fine sand and is used for joints 1/8 inch or wider—it resists shrinking in wide gaps. Unsanded grout is smooth and used for joints narrower than 1/8 inch, common in wall tile, because the sand can scratch polished surfaces.

Do you need to seal grout?

Yes, unless you used an epoxy grout (rare in DIY projects due to cost and difficulty). Unsealed cement-based grout absorbs water and stains. A penetrating sealer fills the pores and repels moisture without changing the grout's appearance.

How do you know when it's time to regrout?

Look for cracks wider than a credit card edge, missing grout that exposes the tile edge, or dark stains that won't scrub away. If you press the grout with your thumbnail and it crumbles or feels spongy, it's time to remove and replace.

This is educational information, not construction or home-repair advice. If you discover soft drywall, widespread mold, or structural damage behind the tile, call a licensed contractor to assess the scope before proceeding.