Common decking problems and their solutions

If you’ve ventured out into the garden of late, you might have spotted a few problems with your decking. If not, you’re one of the lucky ones but unfortunately a clean bill of health now doesn’t always translate into a clean bill of health further down the line. Below are three of the most common decking problems, along with advice on how to diagnose and deal with them.


Mould can often be washed off with a fungicide but it’s just as easy to scrub it with hot soapy water and it’s kinder in an environmental sense. Jet washing will release a powerful spray of water and help you get inbetween the planks but if carried out incorrectly, you run the risk of further damage. If there are any signs of flaking, you’re best off sticking to scrubbing or scraping it to help preserve the wood grain.

Garden decking ideas

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Once the decking’s clean, leave it to dry and apply a clear wood preserver designed for decking or seal it with a sealant. Due to the way the sunlight falls, decking located on the northern side of the home is most susceptible to mould and mildew as southerly sun keeps those fungi-friendly conditions at bay. For mould to grow, there needs to be a food source (pollen, dust or dirt), dampness and a temperature that sits between 4 and 38 degrees Celsius (the exact number depends on which type of mould) with greater than 60% humidity.



If your decking is losing its colour and it’s starting to look worn out, the outside environment is to blame. This type of problem normally occurs after an extensive period of sun and warm weather. While moving it inside is out of the question, you can give it a boost by re-staining with a stain or paint. Remember that hardwood decking ages over time, so cracks and warping are common as wood progresses. It’s good practice to re-treat and seal it every two years to keep it ticking over, with a product such as a stain and wood preserver combination or a water sealer with stain or paint. When you’re painting a specific area, sanding it first will allow it to blend in with the rest of your decking, while a change in colour will require sanding inbetween each coat (at least three), whether that’s a tiny area or the entire deck. The best environment is an almost dry deck so give it a quick wash before you start.

Garden decking kits

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While there’s no saving already rotted wood, you should check the posts and joists for signs of rot (mould, soft wood and water stains) to make sure that the underlying structure isn’t damaged before you replace the planks. When a deck post is placed in the ground, concrete is normally poured around the base to secure the post. Dirt can settle around the post and allow water to build up when it rains, weakening it over time. Water can also build up around the screws and nails which attach the decking planks to the joists and this can work its way through to the wood and the joists below.

Garden decking

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If the rotting hasn’t been present for long, there’s a good chance that it’s isolated to the planks themselves. A quick way to test how much damage has been done is by pressing a screwdriver into the wood. The further it can go without effort, the further the rot has progressed.

Garden design tips

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Bear in mind that a damaged deck with mould can point to a poorly placed source of water such as a gutter which could be allowing water to store on the surface of the deck. There’s no point replacing your wood if you don’t solve the water problem first, so make sure that your gutters are draining through the decking down to the ground below or away from it entirely. If water’s running off the roof, it’s time to invest in better gutters!

If you need help dealing with your decking, post your job in our Carpenter/Joiner or Flooring Specialist category under Wooden Decking. Up to three tradespeople can contact you to quote and you’ll be able to view their profile pages, complete with customer ratings, to help you decide who to hire.

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  1. I want to change back terrace from slabs to Decking, we have South West facing back garden. If anyone can help.

    1. Hi Mrs Graham,

      To find a tradesman to help, you’ll need to post your job using the webform on our homepage: Up to three local tradesmen will then contact you to quote and you’ll be able to choose between them to find a tradesman that you feel most comfortable working with.

      Best of luck!

    1. Hi Caroline,

      For your own protection, I have removed your telephone number from your post. If you’re ready to have decking installed, you can post your job on our main site where up to three local tradesmen can contact you to quote. Our tradesmen do however have to pay for these leads, so if you’re not certain of carrying out the job, I would suggest posting on our Ask an Expert section for a quote:

  2. I had decking fitted and I’m really pleased with it but I have to treat mine every year and it’s a large area so please take this into account. Now I’m getting older it’s a big job for me where if I’d had decorative slabs I could have just used the jet washer 🙂

  3. how can I cover my decking to keep the inside of a planned summer house dry please……..I need to seal the whole inside somehow

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