Moisture and Mould Issues In Garden Sheds

Timber building maintenance is crucial to the longevity of your Shed, Summerhouse or Garage. At this time of the year I am often asked; how do I get rid of black mould? Why is my Shed damp? And what are these white spores appearing?

The answer to that is; stop it from happening in the first place! If you’ve left it too late and you’ve succumbed to the evil mould read on.. 😉

Garden sheds can suffer from moisture and damp issues at certain times of the year. Wooden sheds are even more prone to these problems, as timber is a natural material. Winter and Spring are the main times, when there may be a high level of moisture in the air. This is caused by wet weather and damp conditions.

Effects of moisture are…

• Premature rot
• Mould on interior panels and roof
• Warping and sagging of timber

Preventing Damp Issues

There are a few things that you can do to prevent and minimise the damage which can be caused by moisture.
A cause of rot in garden sheds could be rising damp, this is caused by groundwater being absorbed through the floor bearers and into the floor.  To prevent this from happening it is best sorted during the initial planning stages of siting and building the shed. You will need a barrier between the ground and the floor of the shed, to stop the moisture entering.

How you do this will depend on what type of base you are using on which to position the shed...

• Bases made using gravel allow any rain water to flow freely through it and prevent water from pooling. This reduces the chances of water being soaked up by the floor bearers.
• Timber rafts can be used to raise the shed completely off the ground, so that it is almost impossible for water to penetrate the floor bearers.
• Concrete and paving slab bases need to be as level as possible to prevent water from pooling. A shed that sits in puddled water will inevitably absorb water.

Not only can sheds suffer from ground moisture, but also from moisture in the air. This issue is particularly widespread in Winter. Moisture, caused by damp, wet conditions can get trapped inside sheds, especially if they are not used often. If the outside temperature drops, any moisture inside the shed will cause condensation on the inside of the shed panels, roof, floor and possibly other items stored in the shed. This condensation will cause mould and mildew to form very quickly.

To combat this issue, make sure your building is well ventilated, and allow the shed to vent as often as possible throughout the winter (crucial when you may not use it as much). This will enable fresh air to circulate around the building and stop moisture from building up.  To do this, you can open the windows if you have them or leave the door open from time to time in dry weather.  If your building is over 15m2 and doesn’t already have an air vent or louvres, consider fitting one.

Ensure you do not store wet or damp items in the shed, like garden tools or bikes etc… try to dry them off before returning them to the shed. The slightest bit of moisture stored in your Shed or Garage can cause a whole world of mould problems, especially if you leave it locked up for a couple of months without any ventilation. If you do get mould forming, it is advisable to remove it as quickly as possible with an anti-mould cleaner, before it penetrates and permanently damages the timber.

However, the above may be impossible! If you can’t dry EVERYTHING (!) try using a moisture absorber, such as a dehumidifier or moisture absorbing crystals which attract excess humidity from the air by a simple chemical process.

Keep anything likely to decay off of the floor and walls (paper, cardboard, material) to prevent them from sucking the moisture out of the timbers. Timber likes to breathe so make sure you’re allowing air space around all items in your building –especially in Summerhouses where you may plan to have furniture up against walls.

Single skinned buildings will always be susceptible to moisture, so consider insulating and lining your building. This creates a cavity, a breather membrane and a separate internal lining = moisture blocked. This is a costly alternative so it depends on your own Shed desires.

There you have it! Mould hasn’t got a look in. If you follow these tips and keep up the general maintenance of your building such as preserving your Shed, Summerhouse or Garage annually your ManCave, ShedShed will last you many years to come.