blog feature image for Mouldy Summerhouse? 6 Easy Steps to Combat Mould

Mouldy Summerhouse? 6 Easy Steps to Combat Mould

NattyShedGirl Buyers Aftercare, Summerhouses 1 Comment

Why is my Summerhouse Mouldy?

I’ve answered this question two times already this month and so I thought you know what, those two people can’t be the only ones facing a mouldy Summerhouse?

Over the past few years Scotland has experienced unprecedented  levels of rainfall.

Personally, our specification and the way we make our buildings has completely changed in order to combat this, as well as the expectancy of customer after care. 30+ years of hand crafting wooden Summerhouses, you start to really understand why it behaves the way it does when it is not looked after properly.


Set the scene; you’ve not been in your summerhouse for a while, then one day the sun comes out and off you pop with a cup of tea and that really good book you’ve nearly finished. However, when you arrive the doors are stuck and there is this black mould that has appeared?!

What on earth? How could this be?!

How do I fix this?

There are many ways in which you can prevent moisture building up in a single skinned building (single skinned, ie no insulation or lining).

Firstly ensure your building is properly aired – moisture collects in the timber through ingress and needs a way to escape!! Pin those doors back and get the air flowing. Circulation stops the warm heat staying stagnant inside and creates a through draft which drys the timbers.

When a building is not aired it invites moisture to build up and this creates mould spores. This is particularly evident in buildings were people may store damp (it doesn’t have to be ringing wet to be damp) furniture, gardening equipment, bikes or golf clubs . This mould/blackening is unfortunately now irreversible, however, it can be stopped from spreading any further.

Here’s the method we recommend to rectify this issue…

Mouldy Shed or Summerhouse Treatment Tips

  1. Remove all furniture and fixings from the building.
  2. Apply neat bleach (straight out the bottle, wearing gloves and old clothes with all doors and windows open) with a sponge to all effected areas. This will kill the existing live spores and lighten the blackening considerably (not completely).
  3. Leave the building to air for a day.
  4. Apply an anti-fungal/pesticide to all the timbers inside the summerhouse; we find PermaGaurd works well.
  5. Leave the building to air for a day.
  6. After that, you may wish to apply some colour to the inside to cover up the staining caused by the blackening.

I would suggest using Sadolin Quick Dry watered down to give a classic nautical look like I have done to my show studio. I used Gregorian Grey Sadolin Quick Dry and I watered it down by one third, to give it a light consistency.

Vd lining - scandinavian redwood

Please be aware all online colour charts are not a great representation of the actual colour when on wood

At the end of the day, if you’re reading this blog you’ve already got mould in your summerhouse or timber building.

It’s not the end of the world, the structure itself is fine, it just needs some care and attention and these 6 steps will help you achieve that.

So go on, what are you waiting for?

Show your summerhouse some love. <3