Symptoms
- Visible crack line across the shower floor
- Base flexes slightly when stepped on near the crack
- Water may seep through during use
- Crack may be accompanied by discoloration below
Likely causes
- CommonImpact damage from a dropped heavy objectFiberglass and acrylic bases can crack from a dropped bottle, tool, or shower seat.
- CommonInadequate support beneath the base during installationIf the base wasn't set on a full bed of mortar or adequate support, it can flex and crack over time under weight.
- PossibleAge-related stress crackingYears of temperature changes and weight cycling can crack an aging base even without a specific impact.
- Less commonSettling or movement of the subfloor beneath the baseStructural shifting in the floor joists can transmit stress to a rigid shower base.
What to do
- Assess the crack's size and location; a small, stable hairline crack away from the drain may be a candidate for a patch kit.
- Clean and dry the cracked area thoroughly before attempting any repair.
- For minor cracks, use a fiberglass repair kit, applying filler and gel coat as directed, sanding smooth once cured.
- Press gently around the crack to check for flexing; noticeable give means the support underneath may be compromised.
- If the base flexes or the crack is large or near the drain, avoid a cosmetic-only patch since water will likely still get through.
- For significant flexing or a large crack, plan for base replacement, which usually means removing surrounding wall material too.
- In the meantime, avoid using the shower if water is visibly leaking through the crack to prevent subfloor damage.
Tools and parts
- Sandpaper
- Mixing stick
Fiberglass shower base repair kitSearch: “fiberglass shower pan repair kit”
When to call a pro
Call a contractor if the base flexes underfoot or the crack is large, since a cosmetic patch won't solve a structural or leaking problem.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.