December 30th, 2022 by Sarah Miles

What causes mould in sheds?

Mould and dampness can prove to be a real issue for outbuildings such as sheds, garages, and summer houses. If allowed to take hold, it can be difficult to eradicate fully, leave an unpleasant smell, and ultimately cause the shed to rot. Mould in sheds, just like mould in bathrooms or other areas of the house, is primarily caused by excess moisture. Your shed is especially vulnerable in winter because it’s cold so the air doesn’t dry out and weather conditions like rain, frost, and snow all add moisture.

Why are sheds vulnerable to mould?

Sheds are much more vulnerable to developing mould than your home because of the following issues:

Moisture can’t escape
We tend to shut sheds up tight over the winter, thinking we are doing the right thing for security or for protecting the contents from the weather but, in fact, the structure struggles to ‘breathe’. This means that moisture becomes trapped and makes the whole environment increasingly damp.

Solutions:

• Ventilate the shed to allow moisture to be released. Open windows and doors periodically over the winter, when the weather is dry, or install louvre vents.
• Remove moisture from the air by leaving moisture traps inside. Some even say that cat litter helps. If you have power in the shed, a dehumidifier can be very effective.
• Never leave damp items in there. Leaving items that are wet or even just damp (eg bikes, golf club sets etc) will just add to the moisture in the air. Always allow items to dry completely before storing.

The air can’t dry out
When it’s as cold as it is in the winter, it’s very difficult for the air to get dry and the moisture can’t evaporate.

Solutions:

• If you have power, you can add some low-level heat by using a tubular heater. They are compact, can be wall-mounted, and are energy efficient so you don’t need to worry about running costs. They will take the chill from the air and allow it to dry
• Retain heat better by insulating the shed (if you are using a heater, this also minimises heat loss and, therefore, energy wastage). Insulation materials such as foil-back compression insulation can be very effective but make sure you do it correctly (or get a tradesperson to do it) as incorrectly installed insulation can impact the breathability and actually trap moisture inside.

Contents can become damp
Even if all the contents of the shed are dry when you put them in, certain materials can still absorb moisture from the wood of the floors and walls. Perishable materials such as paper, cardboard, and fabric are particularly vulnerable.

Solutions:

• Pull items, especially things like sofas and chairs in a summer house, away from walls to allow air to circulate around them properly
• Store perishable materials off the floor and away from walls, for example on some racking. Alternatively, bring them into the house for the winter.