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By Cara Mackay on 17 Apr 2016

How to STOP your shed from getting mouldy…

You’ve just wandered into your shed after the winter madness. You’re starting to get the tools out to get stuck into the garden – but here what’s this I spy with my little eye – a little black patch – maybe it’s a spider.

You suspiciously edge in for a closer look … ACH, IT’S MOULD!!! 

How the hell do you get rid of mould in your shed?

Mould is one of our favourite subjects here at Gillies & Mackay. We know that it’s a scourge on timber buildings, and one of the main things putting people off from buying a timber beauty.

How do I get rid of black mould?

Why is my shed damp?

What are these white spores appearing in my shed?

We’re asked these things time and time again. And the answer to that is: stop it from ever happening in the first place! That’s right! Prevention is better than cure, and it’s totally possible to live a mould-free shed life, with a little bit of guidance from the experts (that’s us).

If you’re reading this thinking: “Uh oh, I already have mould in my shed”. Then don’t worry, we’ve already got an article written all about how to get rid of mould from your shed if you’ve got it.

But if you’re here because you’re thinking about getting a timber shed, Garden Room or Garage and absolutely do not want to come across mould in your shed EVER – then read on.

Why does mould form in sheds?

Mould loves moisture. Most sheds are single-skinned buildings with single glazing meaning you typically get moisture build-up and condensation. 

And water gets into even serious sheds like ours. Because timber is naturally porous, it will take in water from the air (especially when it’s raining) and sometimes this water will pass through to the inside of the shed. This is a completely normal situation and should be expected in a single-skinned building.

But during the warmer months, the timber has a chance to dry off quickly. You’re in and out of your shed regularly and the ventilation this provides means that water ingress doesn’t cause any problems.

In the winter months, when your shed is out of use, it’s not getting the air circulation needed and there’s nowhere for the moisture to escape. 

Constant moisture is the prime breeding ground for mould to form in your shed. The key here is to keep your shed dry. 

But how can you do that?

How to Guarantee A Mould-Free Timber Building

To be absolutely 100% certain that water ingress won’t cause mould in your timber building, make sure it isn’t single-skinned. I know. This might seem like a bit of a cheat, especially if you already have a single-skinned shed, summerhouse or garage. But this is the guaranteed best solution to this problem.

How do we know?

Because when water ingress causes issues in a building, we get calls about it. We got so many calls about single-skinned garages over the years that we had to take action. That action was to develop our 3-tiered garage specification, which layers cladding, an air gap, a dampproof membrane and OSB over the framing. This specification is so reliable that it inspired our decision to stop making single-skinned summerhouses in 2023, and replace them with our revolutionary 3-tiered Under 12m2 Garden Rooms instead. We don’t want mould in your building any more than you do!

Top 5 Tips to Prevent Mould in your Shed

But if it’s a single-skinned building you’re set on, prevention is still better than cure, and we want to stop this mould from ever getting a footing in your beloved timber building. So how do we go about that?

  1. Ventilate your shed
  2. Make sure everything is dry
  3. Add moisture absorbers or a dehumidifier
  4. Keep perishables off your shed floor
  5. Add insulation

So let’s go into these in a little more depth.

1. Ventilate your Shed

Ventilation is crucial in the winter months when you may not use your shed as much.

To ventilate your shed: Open the doors and windows periodically in dry weather.

If your building is over 15m2 and doesn’t already have louvre vents, it would be a good idea to fit them. This will allow moisture to escape easily.

2. Anything You Store In Your Shed Must Be Dry

You can’t store damp golf clubs, wet bikes, or sodden wellies in your shed and get away with it you know. The slightest bit of moisture stored in your timber building can cause a whole world of mould problems, especially if you leave it locked up for a couple of months without any ventilation.

Leave them out to dry for a bit or if not – get a dry towel or a good bit of kitchen roll and wipe down your items before placing them back in your shed. 

Any whiff of moisture – the mould spores will be at you!

3. Moisture Absorbers or Dehumidifier

Number 2 was a bit harsh… How can you make sure EVERYTHING is completely dry?! 

You can’t, so you need some sort of moisture absorber – some say Cat Litter works? 

This is my favourite though: The Mega Moisture Trap (it even sounds cool). De-humidifiers work too if you have electrical access to your shed – especially recommended if you use your shed as a workspace.

4. Keep Perishables Off Your Shed Floor

What do we mean by perishables?

Things like paper, cardboard and material. Light moisture passes through timber – perishables absorb and hold moisture meaning they can get damp and stay damp – keeping your shed damp.

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.

5. Add insulation to your shed

Similar to our three-tier specifications, insulation can help regulate temperatures in your shed to minimise moisture build-up. However, it must be added in correctly to ensure breathability otherwise you could end up trapping moisture and causing both mould and rot in your shed.

We still recommend you follow the other tips we’ve shared with you even with insulation. For instructions on how to add insulation to your shed read: How To Insulate Your Shed.

If you’re getting a brand spanking new shed we recommend that you ask us about getting shed insulation fitted.

6. Additional tip: Buy a triple-skinned shed instead

I know, I’m repeating myself! But single-skinned buildings will always be susceptible to moisture. If you haven’t bought your shed yet and want to avoid moisture and mould completely – buy a timber building that is triple-skinned instead! Our 3-Tier Sheds use the same specification as our Garages but also come with a timber floor. While these are a more costly alternative, there’s no better way to keep moisture, and therefore mould, out of your building. If you’d like to know more, read this.

Shed Maintenance is key when it comes to preventing mould…

There you have it! Mould hasn’t got a look in.

If you follow these tips and keep up the general maintenance of your shed your Man Cave, She Shed or Gin Palace will last you a lifetime. And ultimately preventing mould in a timber shed is the ultimate aim.

Learn more on Shed Maintenance: 

If you feel your shed is at the end of its lifespan and you’re not winning the mould or rot eradication fight – it might be time for a new shed that outlasts you. Book a consultation with one of our team to discuss your brand new shed.

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