How to Re-Grout a Shower
Updated February 25, 2026
Remove crumbling or moldy grout and replace it with fresh grout and sealer -- the repair that prevents water damage behind your shower tiles.
Overview
Grout does not last forever. After 10-20 years (or sooner with hard water and poor ventilation), it cracks, crumbles, and develops mold that cleaning cannot remove. When grout fails, water gets behind the tile and into the cement board or drywall. That leads to mold growth on the substrate, soft spots in the wall, and eventually a full tear-out that costs $3,000-$8,000. Regrouting costs $15-$40 in materials and a weekend afternoon. It is the maintenance task that saves thousands in future water damage repairs.
What You'll Need
Safety First
- Wear safety glasses when removing old grout. The grout removal tool throws small chips. An oscillating tool at high speed creates fine dust -- add a dust mask.
- Do not use the shower for 48 hours after grouting. Premature water exposure weakens the grout before it cures fully. Use another bathroom or plan accordingly.
- If you find soft, crumbling cement board or actual mold on the wall surface behind the grout, stop. The substrate is compromised and needs professional assessment before regrouting over it.
Step-by-Step Instructions
- Remove the Old Grout
Use a manual grout removal tool ($8-$12, carbide-tipped blade) or an oscillating multi-tool with a grout-removal blade ($15-$25 for the blade). Score along each grout line, removing at least 1/8 inch of depth -- deeper is better for adhesion. Work carefully to avoid chipping the tile edges. Vacuum the dust and debris from the joints as you go. The goal is to remove all soft, crumbling, and discolored grout down to solid material.
Tip: An oscillating multi-tool is 5-10x faster than a manual tool but requires more control. Set the tool to medium speed and let the blade do the work -- pressing too hard chips tile edges. Practice on a less visible area first. - Clean and Prepare the Joints
After removing the old grout, vacuum all joints thoroughly. Wipe with a damp sponge to remove remaining dust. Check for any soft spots in the cement board substrate behind the joints -- push gently with a screwdriver. Solid? Proceed. Soft or crumbly? That section has water damage and may need cement board replacement before regrouting. Let the joints dry completely (2-4 hours with a fan or overnight) before applying new grout.
Tip: A shop vacuum with a crevice attachment cleans grout joints better than any other method. The narrow nozzle reaches into the joints and removes debris that a sponge pushes around. - Mix and Apply New Grout
Use sanded grout for joints wider than 1/8 inch (most shower floors and some walls). Use unsanded grout for joints 1/8 inch or narrower (most wall tile). Mix to a thick peanut butter consistency -- not runny. Spread grout over the joints with a rubber grout float held at a 45-degree angle, pushing grout into the joints firmly. Work in 3-4 square foot sections. After filling, hold the float at 90 degrees and scrape excess grout diagonally across the tile surface.
Tip: Work in small sections (3-4 square feet at a time). If you spread grout over a large area and it starts to set before you wipe it, removing the haze becomes extremely difficult. The working time for most grouts is 15-20 minutes before it starts to firm up. - Clean and Shape the Joints
Wait 15-20 minutes after applying grout to each section (the grout should be firm to the touch but not hard). Wipe the tile surface with a damp sponge in diagonal strokes -- do not wipe along the joint or you will pull grout out. Rinse the sponge frequently. Two passes: first to remove bulk haze, second to clean. Let the grout cure 24 hours. After 24 hours, a light grout haze may remain on the tile -- buff it off with a dry cloth or cheesecloth.
Tip: The sponge should be damp, not wet. Excess water on the grout surface weakens it and causes color inconsistency. Wring the sponge until almost dry between passes. - Seal the Grout
After 48-72 hours of curing, apply a penetrating grout sealer. Use a small applicator bottle to run sealer along each grout line. Let it soak in for 5-10 minutes. Wipe excess off the tile surface. Apply a second coat after the first dries (1-2 hours). The sealer fills the pores in the grout and prevents water from penetrating. This is the step most people skip -- and it is the reason grout fails prematurely. Reseal every 1-2 years.
Tip: Test the seal after 24 hours by dropping water on the grout. It should bead up, not soak in. If it soaks in, apply another coat. This water-bead test works any time you want to check if your sealer is still effective.
Pro Tips
- Use caulk (not grout) at all change-of-plane joints: where walls meet the floor, walls meet the tub, and wall corners. These joints move with temperature and settling. Grout cracks at these points. Caulk flexes.
- Epoxy grout ($20-$30 per box) is waterproof without sealing, stain-proof, and never needs resealing. It is harder to work with (sets faster, harder to clean off tile) but is the last grout you will ever install. Worth the extra effort for a shower that stays perfect for 20+ years.
- Color-matched caulk is available from grout manufacturers (Mapei, Custom Building Products) so the caulk lines blend with the grout lines. Buy them together for a uniform look.
- If the shower has a niche, bench, or curb, pay extra attention to the horizontal surfaces. These collect standing water and are the first grout lines to fail.
- Pre-mixed grout ($15-$25 per tub) eliminates the mixing step and comes in a consistent color. Slightly more expensive than powder grout ($8-$15) but easier and more foolproof for DIY work.
When to Call a Pro
Call a tile professional if you find water damage behind the grout (soft cement board, visible mold on the substrate, loose tiles), if the shower has extensive tile damage in addition to grout failure, or if you want epoxy grout applied (it requires experience and fast work due to the short working time).
Frequently Asked Questions
When should I call a plumber to re-grout a shower?
Call a tile professional if you find water damage behind the grout (soft cement board, visible mold on the substrate, loose tiles), if the shower has extensive tile damage in addition to grout failure, or if you want epoxy grout applied (it requires experience and fast work due to the short working time).
What are some expert tips to re-grout a shower?
Use caulk (not grout) at all change-of-plane joints: where walls meet the floor, walls meet the tub, and wall corners. These joints move with temperature and settling. Grout cracks at these points. Caulk flexes. Epoxy grout ($20-$30 per box) is waterproof without sealing, stain-proof, and never needs resealing. It is harder to work with (sets faster, harder to clean off tile) but is the last grout you will ever install. Worth the extra effort for a shower that stays perfect for 20+ years. Color-matched caulk is available from grout manufacturers (Mapei, Custom Building Products) so the caulk lines blend with the grout lines. Buy them together for a uniform look. If the shower has a niche, bench, or curb, pay extra attention to the horizontal surfaces. These collect standing water and are the first grout lines to fail. Pre-mixed grout ($15-$25 per tub) eliminates the mixing step and comes in a consistent color. Slightly more expensive than powder grout ($8-$15) but easier and more foolproof for DIY work.
What tools do I need to re-grout a shower?
You will need: Grout removal tool ($8-$12 manual) or oscillating multi-tool with grout blade ($15-$25 for the blade), Rubber grout float ($8-$12), Sanded and/or unsanded grout ($8-$25 depending on type), Sponge and bucket (for cleaning excess grout), Penetrating grout sealer ($8-$12 per bottle), Shop vacuum with crevice attachment (for cleaning joints), Safety glasses and dust mask.
When should I call a professional instead of doing this myself?
Call a tile professional if you find water damage behind the grout (soft cement board, visible mold on the substrate, loose tiles), if the shower has extensive tile damage in addition to grout failure, or if you want epoxy grout applied (it requires experience and fast work due to the short working time).
How difficult is this project?
This project is rated intermediate. It requires moderate DIY skill and the right tools.
How long does this take?
Plan for approximately 4 - 8 hours (spread over 2 days for cure time). First-timers may need extra time.
How much will this cost?
The estimated cost is $15 - $40. Costs vary by location and materials chosen.