What Is Wet Rot?

Wet rot occurs when timber has become damp or moist for an extended period of time. There are many types of fungi which are considered wet rot and they all have one purpose- to break down wood and feed on its nutrients. In turn, this decreases the structural integrity of the wood and your property in general.

The fungus forms fruiting bodies, which disperse clouds of spores. These are carried by natural air currents within a home, allowing wet rot to spread to other areas where it can grow. The spores which land on suitably damp and untreated timber germinate by pushing hollow threads into the timber which are called hypha. The hypha branch out deeper into the wood through smaller, needle-like tubes called mycelium. The mycelium consumes and breaks-down the damp timber into food to sustain the growth of the wet rot.

Unlike dry rot, wet rot cannot expand and grow through masonry, meaning that it generally remains confined to the area in which it started. However, if damp is affecting a large area of timber, it is highly possible that the rot will spread a considerable distance.

Does your home have Wet Rot?

What Causes Wet Rot?

There are three main causes of wet rot: moisture, wood type, and environmental conditions.


Moisture is the primary cause of wet rot. It can come from a variety of sources, such as leaks in a roof, guttering or plumbing, rising damp, or poor ventilation. When exposed to excessive moisture, timber is the perfect environment for fungi to grow and spread.

The most common reasons for a building’s timber becoming moist are:

  • Roof Defects
  • Internal Defects
  • Wall Defects

Wood Type

The type of wood used in the construction of a building can also contribute to the development of wet rot. Softwoods like pine and cedar are more likely to fall victim to wet rot than hardwoods, like oak and teak. Softwoods are more porous in nature and naturally have a higher moisture content, making them an ideal breeding ground for fungi.

Environmental conditions

Factors including temperature and humidity can also affect the growth of wet rot. Wet rot causing fungi thrive in warm, damp conditions, so buildings located in areas with high rainfall, high humidity or low ventilation are more likely to suffer from wet rot.

Preventing wet rot requires identifying and eliminating the source of moisture, treating affected areas with fungicidal treatments, and ensuring proper ventilation and drainage systems are in place. By understanding the causes of wet rot, homeowners, and builders can take the necessary steps to prevent this potentially-destructive condition from occurring.

causes of wet rot

What are the Consequences of Wet Rot?

Wet rot can have severe consequences for the structural integrity of buildings and structures. If left untreated, wet rot can cause serious damage to buildings and be costly to repair.

One of the primary consequences of wet rot is the weakening of timber. As the fungi spread, they consume the wood’s primary strengthening components: cellulose and hemicellulose. This in turn causes the wood to become soft and structurally vulnerable, compromising the overall integrity of a building.

Wet rot can also affect the aesthetic appearance of buildings. As the fungi spread, they can cause discolouration and staining on walls and ceilings, as well as leaving a damp, musty odour. This is a major issue in homes and commercial buildings, where the appearance and smell of the property can impact its value.

Another danger of untreated wet rot is the potential for the fungi to spread throughout the building. This can cause further damage and create a hazardous environment for occupants, as the weakened structures can collapse or become unstable.

If left untreated, wet rot can attract other pests and insects, such as termites, which can further weaken the structure and cause additional damage.

consequences of wet rot

What are the Signs of Wet Rot?

Wet rot is a progressive and aggressive maintenance issue. Untreated, it can cause significant and widespread damage to any home which is why it’s essential to act fast whenever you suspect a problem.

Here are the key signs of Wet Rot:

  • Discoloured and darkened timber skirting boards, architraves, or floorboards
  • Movement in the floor or bounce
  • Discovery of fungus which is skin-like in appearance and yellow or dark brown
  • A stringy fungus which bleaches the wood which it affects
  • Wood that appears soft, spongy or crumbles easily
  • A musty, damp odour
  • Wood that has become warped, twisted or distorted
  • Cracks or splits in the timber
  • Wood that feels damp or moist to the touch
  • Paint or varnish that has peeled or flaked away from the wood
  • Evidence of moisture or water damage in the surrounding area, such as water stains on walls or ceilings.

Wet Rot Treatment

Where wet rot is discovered, the badly decayed wood which is beyond repair should be removed and disposed of as a first action, no matter where the rot is found. This is the first step in wet rot treatment.

We then use the ALLDAMP Timber Treatment Solution to reduce and stop the spread of the further rot due to the already affected timber. Any wood which is not removed needs to be treated with a suitable timber preservative and any timber used to replace the old should be pre-treated against fungal decay. This makes sure that the fungus does not return.

The above, however, does assume that the cause of the wet rot – the damp – has been solved. For more information about damp treatment, visit our damp proofing page.


How can I tell whether a fungus is Wet Rot?

We have listed some common signs of wet rot above on this page, but you should always seek an expert opinion. wet rot can pose serious danger to you and anyone living in the property, and we would advise undergoing wet rot treatment.

Is Wet Rot dangerous?

The fungus that causes wet rot is not directly dangerous to our bodies or our health. However, the damage it causes to timber is a risk and makes it a considerable danger in the home. It’s not uncommon for wet rot to cause considerable damage to floors or the structure of a building.

Does timber affected by rot always need to be replaced?

The need to replace timber affected by an outbreak depends on the severity of the infestation and the duration of the damage. As the rot progresses, the timber loses strength, and if it becomes unable to support weight, replacement is necessary. Our surveyors evaluate the extent of the damage and strive to minimize replacements to reduce costs. If replacement is unnecessary, our team applies a specialized fungicide to treat the affected timber.

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