What causes wet rot? Signs of wet rot and treatment tips

Read on to discover wet rot signs, what causes wet rotand how to prevent it spreading.

Updated 23 July 2019

Wet rot: steaming red mug on the window sill of a window covered by condensation.

Key steps 

  • A leaky roof, burst pipe and more could cause wet rot.
  • Look out for localised fungus, bleached timber, soft spongy wood or damaged, flaky paint, which are wet rot signs.
  • Check which wood decay you are dealing with. 
  • Call in a professional for treatment options.
  • Treat unaffected timber to protect it.

Wet rot can affect wood in your house where there is contact with water or moisture. If left untreated, it can lead to serious damage. Here you’ll find a guide to wet rot signs, what causes wet rot, and how to prevent and treat it. 

The most important thing when dealing with wood decay is being able to tell the difference between wet and dry rot. Read our sister article on dry rot signs and treatment for more detail on that type of decay.

What causes wet rot?

Wet rot is a type of wood decay caused by fungus, naturally occurring in the presence of high moisture levels. There are several reasons your timber could have wet rot. These include:

  • A leaky roof
  • Burst pipes
  • An incorrectly connected washing machine
  • A leaking bath or shower

How to spot wet rot signs

As there many different forms of wet rot, it can be quite difficult to identify wet rot. You also need to take care to identify if it is a more serious case of dry rot. For details on identifying and getting dry rot treatment, click the link in the top tip. Here are some wet rot signsto keep an eye out for.

  • Localised fungus growing on timber. 
  • If you have wet rot, the timber will feel soft and spongy, even if covered in paint.
  • Timber looks darker than surrounding wood in most cases, however some types of wet rot cause wood to bleach.
  • When dry, the timber cracks and crumbles.
  • Timber affected by wet rot can also be susceptible to shrinkage.
  • Damaged or flaky paint could increase your risk of wet rot. To check if timber beneath paint has wet rot, push a thin bladed knife into the wood. The blade should stop almost immediately, but if you find it pushed all the way through to the handle, it’s likely to be a case of wet rot. 
  • Wet rot will leave behind a damp, musty smell.
  • The colour of the timber decay will be different to dry rot and is an easy way to differentiate the two.

Steps for wet rot treatment

There are a few important steps you will ned to take when it comes to wood rot treatment:

  1. Firstly, you need to ensure which type of decay you are dealing with.If you are sure it is wet rot, read on. If you believe it might be dry rot, click here to find details of dry rot signs and treatment.
  2. Try and find out what the cause of the decay is. Wet rot will be caused by moisture in the area, so look in the surrounded area to find the cause.
  3. You will want to check with a professional for treatment options.If timber has lost its integrity due to the wet rot, it will need to be removed and replaced. This is especially important where timbers are used to ensure the structural integrity of your home.
  4. Treat unaffected timber to protect it. All surrounding wood will need to be treated with a wood hardener and preservative. This will help prevent the spread of wet rot.
Originally published 11 July 2019