Two things drive kitchen mold. Cooking puts a lot of moisture into the air, and if the extractor recirculates rather than vents outside (or is not used), that moisture condenses on cool surfaces and the ceiling. And the kitchen has more concealed water connections than any room — under the sink, behind the dishwasher, the fridge water line, the washing machine — where a slow leak soaks the cabinet base and the wall behind unnoticed.
Key takeaways
- A recirculating or unused extractor lets cooking steam condense and grow mold.
- Under-sink and behind-appliance leaks are the most common hidden source.
- Check cabinet bases and the wall behind the fridge and dishwasher.
- A musty smell from a cabinet is a leak signal.
Cooking steam and extraction
Boiling, steaming and frying release water vapour continuously. A ducted extractor hood vented to outside removes it. A recirculating hood (charcoal filter, no external duct) removes smells but returns the moisture to the room. If your hood is recirculating, or is not switched on, that steam condenses on the coolest surfaces — the ceiling, wall cabinets on an external wall, and the window — and grows mold there.
Concealed leaks
- Under the sink — tap tails, the trap, the waste connection, and the shut-off valves.
- Behind the dishwasher — the supply line and the drain hose connection.
- The fridge water/ice line — a slow drip behind an appliance that is rarely moved.
- The washing machine — inlet hoses and the standpipe.
These leak slowly into cabinet bases and the wall behind, and the first sign is often a musty smell when you open the cabinet.
What to check
- Empty the under-sink cabinet and look and feel for damp on the base and back panel; check for staining and swelling.
- Pull the dishwasher and fridge forward (carefully) and check the floor and wall behind.
- Look at the ceiling and the tops of wall cabinets for speckling.
- Check whether the extractor hood actually vents outside.
Fixing it
Repair any leak and dry the cabinet and wall fully — swollen particle-board cabinet bases usually need replacing. If the extractor recirculates and the kitchen has a mold problem, ducting it to outside (or fitting a proper wall/window extract) solves the steam side. Keep humidity down and the kitchen ventilated while cooking.
A swollen, delaminating cabinet base under the sink has been wet for a long time. Replacing the panel without finding and fixing the leak just wets the new one.