Bathroom Mould and Grout in Ontario Homes
Bathroom mould and grout discolouration are among the most common issues Ontario homeowners raise when requesting a deep clean. Ontario's humid summer climate and cold winters (which drive people indoors and into hot showers) create a perfect environment for bathroom moisture accumulation. Here's what's actually causing it and what works to remove it.
Why Ontario Bathrooms Get Mould So Fast
- Closed-up winters: From November to April, bathroom windows stay closed — without fresh air ventilation, moisture from showers has nowhere to go except into grout, silicone caulk, and ceiling corners
- Exhaust fan inefficiency: Most Ontario homes have bathroom exhaust fans that are either inadequate for the bathroom size or haven't had the filter cleaned in years — a clogged exhaust fan is barely better than no fan at all
- Silicone caulk: Silicone caulk at the tub/wall junction is the fastest mould site in any Ontario bathroom. It cannot be cleaned once colonized — it needs to be replaced
What Actually Removes Bathroom Mould
- Surface mould on tile: Hydrogen peroxide (3%) or oxygen bleach (borax-based) applied and left to dwell for 10–15 minutes, then scrubbed with a grout brush. Never use bleach on coloured grout — it strips the colour
- Deep grout mould: Professional-grade enzymatic penetrating cleaner, then a grout re-seal application to slow recurrence
- Mouldy silicone: Remove and replace. There is no effective cleaning solution for colonized silicone caulk — cleaning the surface removes appearance but not the root growth
Prevention
The single most effective step: run the exhaust fan for 20 minutes after every shower. The second most effective: squeegee the shower walls after each use. Both together dramatically slow grout mould accumulation.