Learn how to clean up the exterior of a shed that looks tired

Interestingly, I just had to clean and tidy up the outside of a large shed that had not been painted with stain or Creocote (the creosote replacement) since it was installed ten years ago. The shiplap was still in excellent condition with no rot but the shed treatment had completely faded and algae had begun to take hold. To deal with this properly – what a job you’re thinking. Well actually, no it was easy! It’s not something to struggle with you’ll be excited to hear. That is, if you follow this guide and use the right tools.

Key information:

Use a petrol pressure washer to blast your shed clean
Do I need an Algae / Moss killer if I am using Creocote or Timber treatment?
How to apply the Crecote to your shed? I used a garden sprayer.
How much Creocote will I use?
What to do if you have some rot in my shed?
Don’t forget to clean up after your shed exterior is sorted.
Key preparation and what you’ll to make shed cleaning easy

Use a petrol pressure washer to blast your shed clean

WARNING: Be careful and do a little test patch first. From personal experience if your timber is soft you can literally blow a hole in your shed :). Not that it’s a problem really because if rotten you need to remove that decayed timber anyway but it’ll come as a shock!

You’ll literally be amazed at the capability of a petrol pressure washer when it comes to stripping the old remaining treatment, algae, and dirt off your shed. Be careful though, when I ventured too close with the nozzle I actually began to bite into the timber so make sure you start with a test patch to be sure this method is for you. To say I was amazed by the cleaning performance of my Wilks 750 petrol pressure washer would be an understatement. Here’s a look at this shed blasted clean and coated up compared to the side which has yet to be dealt with. I would say any powerful pressure washer is fine, as long as it has the grunt to clean off your timber. I just know my Wilks pressure washer did it on half power so no stress on the motor either. From the angle the difference is pretty apparent and impressive.

It took me a little over half an hour to blast down one side. Warning, I did this in the middle of Winter and ended up wet, cold, and not in the best of moods. This is most definitely a job for Spring or Summer and not just because of the cold. I had to wait three weeks for a clear run of weather and the timber on the shed to be completely dried out. This is imperative because you’ll want the Creocote to bite in deep for a beautiful, long-lasting finish, or, if you prefer, a more natural wood finish or stain and in which case you might like a wood preservative for sheds.

Do I need an Algae / Moss killer if I am using Creocote or Timber treatment?

From personal experience I would say no, don’t bother. You can save your money if you blast the shed with a pressure washer and especially if you’re using a timber treatment that has the ability to kill fungi and bacteria in the timber.

How to apply the Crecote to your shed? I used a garden sprayer.

I used a pressure type garden sprayer and it worked superbly. A warning. You must wear some kind of mask that really protects you from the vapour as well as some gloves and sensible footwear. I wore my wellies. Read the safety instructions clearly. Although Creocote isn’t as potent as creosote, I highly recommend giving it the same respect. It’s nasty stuff and it really works to treat your shed.

The next bit of golden advice is to ensure you lay a dust sheet with plastic lining, or plastic sheeting to protect your floor. I promise you that not following this step will be disastrous, especially if you have a patio or lawn you are proud of! Although the garden sprayer is quick, it is messy. I wouldn’t blame you for brush application with the knowledge already in hand now. You will get it everywhere – well I certainly did but the speed made it totally worthwhile. I had a double garage size shed side covered heavily in twenty minutes once setup!

Don’t panic, my shed started off a boring looking brown before it dried. Not the nice shiny colour I was hoping for at all. Eventually when everything dried out it looked super and just how I had envisaged it. In the picture below you can see the shiny starting to come through but not quite there. It’s a much nicer look now so don’t panic that you’ve made the wrong choice. The Creocote I used was dark brown for reference.

How much Creocote will I use?

That’s up to you but one side of this shed which is 5.5 metres wide and 2.5 metres tall used 4 litres. There was a significant amount of wastage using the garden sprayer and I really really coated it up. I daresay someone frugal would get away with half but the results were fantastic as you can see from the before and after imagery I have included.

So with my calculations in mind you can get about 3.5m2 out of 1 litre. The sprayer coated at least twice and this coverage is the lower end of manufacture guidelines so seems fine to me too.

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What to do if I have some rot in my shed?

You’ll want some wood filler. Personally I like using Ronseal wood treatment in conjunction with Ronseal wood filler that you can find in the link provided. Some may consider Ronseal wet rot hardener if the decay is really bad to stabilise the timber.

Treat and stabilise the timber. Then apply the putty. Simply sand smooth and then cot. The reason I love Ronseal the most is I know from personal experience that it covers with shed stain and wood oil very nicely so tidies in well not leaving an obvious sign of the rot that was there before.

Don’t forget to clean up after your shed exterior is sorted

Throw away that plastic sheeting as soon as you can. I bagged mine up in some sacks that didn’t have any holes. I gave the patio a blast power with the washer after all had dried up to get up any of the spots of Creocote.

Key preparation and what you’ll to make shed cleaning easy

All in all cleaning the shed exterior was a rewarding job that made a nice difference to the aesthetics of my garden. I would highly recommend using a pressure washer if you can but I am certain sandpaper and a treatment would work too like Cuprinol 5 star. The garden sprayer is a time choice. If you want a fast superb looking job then use it. Once the Creocote fully dries you’ll sit back and look at a job well done. Next I’ll tackle the shed roof and document that as well.

About Terry Smith

I’m Terry Smith from gardentoolbox.co.uk, a professional landscape designer, hobbyist gardener, and barbecue fanatic with 20 years experience building and restoring. So as you go through my site you'll watch me document some of the professional garden installs I make as well as the major projects I take on at home. While sharing those experiences and guiding you, I'll be recommending some great tools I use to enable this along the way so you can really buy in confidence. Always feel free to pop me a message: info@gardentoolbox.co.uk

View all posts by Terry Smith

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