Short answer
Repair if the crack is small, purely cosmetic, and the base is solid with no flex or signs of leaking. Replace if the shower floor flexes underfoot, the crack runs through high-stress areas (around the drain or corners), there are multiple or growing cracks, or any evidence of water intrusion or subfloor damage.
How to make the call (context and criteria)
The right choice depends on two things: what the floor is made of and whether water is getting past the surface.
- Acrylic/fiberglass pans: Hairline or chip damage can often be repaired. Flexing or long cracks usually means the pan lost support and needs replacement.
- Tiled shower floors: A single cracked tile can be swapped if the substrate is solid. Hollow-sounding or loose tiles, widespread grout cracking, dark/damp grout, or movement usually means the waterproofing or mortar bed has failed and a rebuild is the reliable fix.
Quick tests and what they tell you
Identify material
- Smooth one-piece with a flange = acrylic/fiberglass (or solid-surface/cultured marble).
- Grout lines = tile over a mortar bed or foam tray with waterproofing.
Check for movement
- Stand near the crack and gently shift your weight. Any flex or crunching suggests compromised support. Repair won’t last.
Look for leak evidence
- Stains or peeling paint on the ceiling below.
- Musty odor, cupping baseboards nearby.
- Use a moisture meter on drywall below and framing if accessible.
Perform a simple dye/flood test
- Insert a test plug in the drain, add a few gallons of water tinted with food coloring to just cover the crack, and watch below for drips for 30–60 minutes. If it leaks, plan for replacement or full rebuild.
Diagnostics pointers
- Moisture meter wood reading: >15–20% MC suggests a leak.
- Proper shower slope: 1/4 inch per foot toward the drain.
Decision guide
Acrylic/fiberglass pan
- Repair: Minor gelcoat chips, hairline surface cracks, or a short crack in a non-flexing area. No leak detected. Cost $25–$80 in materials; 2–4 hours.
- Replace: Pan flexes, crack near drain or corner, multiple or growing cracks, underside not accessible to reinforce, or dye test shows leak. Pan $200–$800; labor $500–$1,500+ depending on tile walls and plumbing.
Tiled shower floor
- Repair: One or two cracked tiles with a firm, non-hollow bed; no leak signs. Tile/adhesive/grout $30–$150; 2–6 hours.
- Rebuild: Widespread loose tiles, hollow sounds, recurring grout cracks, stains below, or poor slope. Expect $3,000–$10,000+ depending on size, finishes, and local rates.
Step-by-step: Small acrylic/fiberglass crack repair
Only proceed if the pan is solid and no leaks are detected.
Tools/materials
- Color-matched acrylic/fiberglass repair kit (gelcoat or acrylic), or 2-part epoxy + fiberglass cloth for reinforcement
- Drill with 1/8" bit (for stop-holes)
- Rotary tool with small burr or V-groove bit
- Sandpaper: 120/220/400/800+ grits; polishing compound
- Acetone, clean rags, masking tape
- Nitrile gloves, safety glasses, N95
Steps
1. Clean the area with a non-abrasive cleaner; degrease with acetone.
2. If the crack is propagating, drill tiny stop-holes 1/8" at each end (do not drill through the pan; just the top layer) to prevent spreading.
3. V-groove the crack lightly with a rotary tool to accept filler. Mask around the repair.
4. If underside access is available and there’s slight flex, apply a patch of epoxy and fiberglass cloth underneath to stiffen the area. Let cure per product instructions.
5. Mix and apply gelcoat/acrylic filler or epoxy to the V-groove. Slightly overfill.
6. After full cure, sand progressively (220 → 400 → 800) and polish to blend.
7. Inspect after a few days of use for any hairline returns.
Tip: Many kits offer tinting to match white/bone/almond—test on a scrap card first.
Step-by-step: Replacing a single cracked floor tile
Proceed only if surrounding tiles are well-bonded and the surface is firm.
Tools/materials
- Oscillating multi-tool with carbide grout blade, or manual grout saw
- Small cold chisel and hammer; margin trowel; 1/4" notched trowel (as needed)
- Replacement tile, thinset (or rapid-set) and matching grout; grout float and sponge
- Shop vac with HEPA filter; painter’s tape; knee pads; N95 and eye protection
Steps
1. Remove surrounding grout with the oscillating tool—avoid cutting into adjacent tiles.
2. Tape off nearby tiles; score the cracked tile; chisel out pieces from the center moving outward.
3. Scrape and vacuum the old thinset. The bed should be firm; if it’s crumbly or damp, stop and reassess—likely a bigger issue.
4. Test-fit the new tile for height and slope continuity.
5. Set with thinset, maintain proper slope to drain. Allow to cure, then grout.
6. Re-caulk floor-to-wall joints with 100% silicone, not grout.
Safety considerations
- Wear eye protection and an N95/respirator when cutting or sanding (silica and fiberglass dust).
- Use gloves and adequate ventilation with solvents and epoxies.
- Avoid standing or applying heavy pressure on a cracked pan—use a kneeling board to distribute weight during repair.
Best-practice tips
- Movement kills repairs. If you feel flex, address support from below or plan replacement.
- Do a dye test before and after repairs to confirm no leaks.
- For acrylic bases, check manufacturer guidance—some specify compatible fillers and polishing methods.
- Use 100% silicone at change-of-plane joints; re-grout is not a fix for movement.
Common mistakes to avoid
- Smearing caulk over a structural crack—water will find a way.
- Skipping stop-holes on a running crack in acrylic/fiberglass.
- Overusing expanding foam for support; it can distort the pan. If you must, use low-expansion foam sparingly and only with underside access and backer support.
- Replacing a cracked tile without addressing a hollow, unstable bed.
When to call a pro
- You detect leaks, high moisture readings, or ceiling damage below.
- The pan flexes or cracks are near the drain/edges.
- Multiple tiles are loose or the floor sounds hollow.
- You lack access below but suspect subfloor damage.
- Insurance may be involved due to water damage.
A quick assessment with a flashlight, a moisture meter, and a dye test will usually tell you which path to take. Small, stable defects can be repaired. Flex, leaks, and widespread failure point to replacement or a full rebuild for a long-lasting fix.