Table of Contents
• Why Shower Grout Grows Mould in the First Place
• Does Mould Resistant Grout Actually Stop Mould?
• Epoxy Grout vs Cement Grout for Showers
• Grout Sealer for Shower Walls: Do You Need It?
• How to Clean Mould From Shower Grout
• Shower Grout Maintenance That Prevents Repeat Growth
• Fixing the Moisture Source Before You Regrout
• Frequently Asked Questions
Last Updated: November 1, 2026
Why Shower Grout Grows Mould in the First Place
Mould in shower grout isn't really a grout problem. It's a moisture problem that shows up in the grout first because grout is porous and sits right where water hits and stays. Warm, wet surfaces that never fully dry give mould exactly what it needs.
Here's what usually feeds it. Hot showers release steam that settles on tile and grout lines. If the bathroom doesn't clear that moisture within a reasonable window, the grout stays damp for hours. Cement-based grout absorbs water into tiny pores, and those pores become a comfortable home for mould spores.
Watch for the signs: dark specks or fuzzy patches in the corners, lines that look grey even after scrubbing, or a faint musty smell that comes back a day after cleaning. If a clean grout line turns dark again within a few days, the moisture source is still there.
The fix starts with airflow. For more on the wider bathroom moisture causes behind grout mould, read our homeowner's guide to stopping bathroom mould growth .
Does Mould Resistant Grout Actually Stop Mould?
Mould resistant grout for shower walls does reduce growth, but it does not make a shower mould-proof. Some grout products include antimicrobial agents to slow mould colonization on the grout surface. That helps, especially in showers where moisture lingers.
What it won't do is stop mould from growing if water sits on the surface for long periods or if the room never dries out. Once the additive is worn down by cleaning products or time, the protection weakens. Treat it as one layer of defence, not the whole plan.
In practice, mould resistant grout works best when paired with good ventilation and a regular cleaning routine. If your shower still grows mould after you switch, the ventilation is the first thing to check. A Moisture Defense Package may be worth a look for the airflow side of that equation.
Epoxy Grout vs Cement Grout for Showers
Epoxy grout and cement grout handle moisture very differently, and the choice affects how often you'll deal with mould.
Cement grout is the traditional, budget-friendly option. It's easy to install and widely available. Its downside is porosity: it absorbs water, which makes it more likely to stain and grow mould over time. It usually needs sealing and more frequent cleaning.
Epoxy grout is non-porous, so water and soap sit on the surface instead of soaking in. It resists staining and mould better than cement, and it doesn't need sealing. The trade-offs are cost, a harder install, and a tendency to be less forgiving during application. It also cures fast, so you'll want to work in small sections.
Pros and cons at a glance:
Grout Type
Pros
Cons
Best For
Cement (unsealed)
Low cost, easy to work with
Absorbs water, needs sealing, mould-prone
Dry, well-ventilated bathrooms
Cement (mould resistant)
Additive slows growth, familiar
Protection wears off over time
Moderate moisture, budget projects
Epoxy
Non-porous, no sealing, strong stain resistance
Higher cost, tricky install
Heavy-use showers, high-moisture rooms
Application matters too. Epoxy needs a clean, dry surface and tight timing. Cement needs proper curing before sealing. Get the install right and either option performs well.
Grout Sealer for Shower Walls: Do You Need It?
If you choose cement grout, you almost certainly need a sealer. Sealer fills the pores so water beads on the surface instead of soaking in. That reduces staining and makes cleaning easier.
Sealer is not a substitute for ventilation. It slows moisture absorption, but a shower that stays wet will still grow mould eventually. Reapply it according to the product's instructions, usually every one to two years depending on use. Test the product on a small area first, since some sealers can darken grout.
If you use epoxy grout, you can skip sealer entirely. Epoxy is already non-porous, so there's nothing for a sealer to do.
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How to Clean Mould From Shower Grout
Start by ventilating the room and wearing gloves and eye protection. Use a cleaner made for mould on grout, and follow the label. Apply it, let it dwell as directed, then scrub the lines with a stiff brush. Rinse well and dry the area.
A common mistake is scrubbing with too little dwell time. The cleaner needs time to break down the growth. Another is mixing products, which can create dangerous fumes. Use one cleaner at a time.
If mould keeps returning to the same lines within days, cleaning alone won't fix it. The source of moisture has to be addressed.
Shower Grout Maintenance That Prevents Repeat Growth
Prevention comes down to routine. Wipe down the walls after showers, squeegee water off the tile where you can, and keep a regular cleaning schedule. Check grout lines monthly for discolouration or soft spots.
Run your bathroom exhaust fan during and after showers. Leave it on long enough to clear the steam, not just until the mirror looks clear. Many homeowners switch it off too early, which leaves moisture trapped in the grout. Keeping the fan clean and in good working order helps. Our guide on how to clean and maintain bathroom exhaust fans covers the steps. For a specific rule of thumb on how long to run the fan after a shower, see why running the bathroom fan after a shower matters . If you are considering a fan upgrade, the Your Fan Your Way option is worth a look.
Replace cracked or missing grout promptly. Water gets into gaps and feeds growth out of sight, so small repairs now prevent bigger problems later.
Fixing the Moisture Source Before You Regrout
Regrouting a mouldy shower without fixing the airflow can leave the same damp conditions in place, and mould may return. Our page on bathroom fan humidity control after showers explains how airflow and a humidity sensor can work together to keep moisture from returning to the grout.
Homeowner inspecting a bathroom exhaust fan to prevent moisture before applying mold resistant grout
Start by checking the fan itself. A fan that is noisy, weak, or outdated may not be clearing steam properly. If the bathroom still feels damp long after showers, or if you see condensation on the ceiling, the fan is likely the problem. Our guide on how to tell if your bathroom fan needs replacement explains the warning signs.
Once airflow is sorted, regrout if needed, choose the right grout type for your situation, and build a cleaning routine around it. Addressing the source first means the new grout has a fair chance to stay clean.
Bathroom Fan Pros serves homeowners across approved Lower Mainland zones in British Columbia. If your fan is not clearing moisture, you can check current service eligibility and request a quote through our website before you spend money on grout.
Frequently Asked Questions
What is the best mould resistant grout for shower walls?
Epoxy grout is generally the strongest choice for shower walls because it is non-porous and resists water, staining and mould far better than standard cement grout. Many manufacturers also sell cement grouts with added mould inhibitors, which help but do not replace good ventilation. Compare product specifications, check that the grout suits your tile joint width, and ask your installer which option they recommend for your shower's conditions. Current product prices vary by brand and quantity, so check with your supplier before buying.
Is epoxy grout better than cement grout in a shower?
For most showers, yes. Epoxy grout does not absorb water, so there is little for mould to feed on, and it resists staining from soap and hard water. It is harder to install and costs more per bag than cement grout, and it needs careful mixing and clean-up. Cement grout is workable and widely available, but it is porous and needs regular sealing to perform well in a wet shower.
Does mould resistant grout stop mould from growing?
It slows growth but does not stop it on its own. Mould needs moisture, warmth and a food source such as soap scum. Mould-resistant grout removes some of those conditions, but a shower that stays damp because the fan is weak or missing will still grow mould. Pair the grout with proper exhaust ventilation, regular cleaning and, where recommended, a grout sealer.
Do shower walls need grout sealer?
Cement-based grout usually does, because it is porous and absorbs water and soap residue. Sealing reduces staining and slows moisture penetration. Epoxy grout generally does not need sealing. Check the manufacturer's instructions, and reseal according to their recommended interval, which is often every one to two years depending on use and cleaning habits.
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