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Wet rot is a form of wood-decaying fungi that can cause structural damage in buildings by weakening timber in areas with a persistent source of moisture. Over time wet rot can cause timber to lose its structural integrity, often causing joists, floorboards and other sections of timber to become weak and spongy.
Our guide has been designed to help identify a wet rot problem, what might be causing it and how to prevent it from returning. If you think you have a wet rot problem, you may require a professional damp and timber survey to further investigate. This is important in order to fully understand the extent of the damage and the source of moisture causing the problem.
Rentokil Property Care have a number of CSRT and CSTDB qualified surveyors who are experts in wet rot identification, and will provide you with detailed recommendations for remedial work to remove the moisture source and treatments, if required.
We are Property Care Association Members and have a number of branches across the United Kingdom, meaning we have qualified and experienced surveyors and technicians local to you.
Wet rot is the term used to describe most of the fungi we see in nature, that degrade the strength of timber exposed to water, and can cause it to weaken, crack and over time become structurally compromised.
The different types of wet rot will consume moisture and nutrients from the damp timber which causes it to become decayed. It is typically confined to the source of moisture and will not spread further, while typically requiring wood with a moisture content of 50% to 60%.
Wet rot spores germinate on the surface of wet timber, causing the life cycle to repeat.
The main difference between wet rot and dry rot is that wet rot requires a higher moisture content in timber, typically around 50% to 60%. Dry rot spores can germinate on timber with a moisture content of as low as 20%, but typically 30% to 40% is optimum for growth.
Dry rot can also be far more destructive than wet rot, this is because dry rot can spread away from the source of moisture in search of new timber to attack, while also being capable of spreading through masonry. Typically wet rot is isolated at the source of moisture and will not spread through masonry. Because of this, different treatment methods may be required, as the extent of the problem can vary depending on the type of rot.
Wet rot is still capable of significant damage to a property, especially if left over long periods of time. Both are common in sub floor voids where there are often damp conditions and a lack of air flow. Because of the differences between wet rot and dry rot and the treatments required, correct identification is essential.
While dry rot is typically seen as more destructive as it can spread through walls and across surfaces, both types of rot can lead to severe structural damage of timber.
Dry rot mycelium and strands can grow, spread and carry nutrients through masonry, behind plasterwork and across steelwork. This means that while wet rot can severely damage timber in an isolated area, dry rot could, if left undisturbed, spread and destroy whole sections of timber in a property, including across different stories.
In sub-floor voids and basements with compromised ventilation, it is not unknown for both types of rot to extend across the building footprint. But dry rot will always spread further and more rapidly, as it can move away from the original moisture source.
Once any form of rot has taken hold it is essential that a professional survey is carried out to fully understand the extent of damage, and to assess whether structural timbers need to be replaced.
While wet rot is the general term for most species of fungi we see in nature and that will degrade the strength of wood and timber, they are generally divided into two types, brown rots and white rots.
White rots will use enzymes to feed on both the cellulose and lignin content in the wood whereas brown rot will only digest the cellulose.
Brown rots are darker in appearance compared to white rots and because they only digest the cellulose, and leave behind the lignin, this makes timber shrink and crack. This causes it to turn brown and become dry and brittle when touched. The most common form of brown rot is Cellar fungus, known as Coniophora puteana.
White rots are a type of timber decay that can appear white in colour. Unlike brown wet rot it will consume both the cellulose and lignin, meaning timber becomes soft, fibrous and pulp-like, meaning it is spongy when touched. Oak fungus (Donkioporia expansa) and Phellinus contiguus are two common types of white rot.
While not being a white rot or brown rot, some types of fungi can form on saturated building materials such as plaster and masonry. These types of fungi can feed on detritus rather than wood or structural timber.
This makes them visible both inside and outside of properties, and common in rooms where moisture is produced like bathrooms and kitchens. They can often be found growing near leaking showers, behind toilets or growing out of cracks in external renders. One of these is Peziza, otherwise known as plaster fungus or 'Elf cup.'
Wet rot will occur when timber is saturated with water over a period of time. When moisture is absorbed into the timber and the moisture content of timber is optimum, wet rot spores that are always present in the atmosphere all around us will land on the surface and germinate. The fungi will begin to grow and develop tiny threads known as hyphae, and over time these develop into a larger mass known as mycelium. Mycelium excretes enzymes onto the wood surface to break it down and absorb nutrients, which in turn breaks down the structure of the wood.
This causes it to lose its structural integrity, and can lead to floorboards, joists and other structural timbers becoming weak and damaged.
Wet rot is common in the UK because of the high levels of rainfall and the varying age of housing stock which often have building defects, allowing moisture to enter the property. Many properties are of solid wall construction, often without adequate damp proof courses and built using structural timber.
Wind driven rain can penetrate into masonry buildings, and will affect properties with defects, or those where regular maintenance is not carried out, defects like cracked masonry, broken plumbing or guttering and leaking downpipes provide entry points for moisture. These defects allow water to collect and then penetrate into the fabric of the property, causing timber to become saturated, providing the conditions for wet rot spores to germinate.
While regular maintenance can help prevent wet rot issues, often the problem is hidden under floors or in roof spaces. This means that the problem can go undetected until there is severe damage and structural failure. A professional survey can help investigate the full extent of the problem and provide answers.
Wet rot can often be difficult to spot until it is too late, as it is often hidden out of sight, in concealed areas of your property. It is common in below ground spaces, in sub floor voids, behind skirting boards in contact with damp masonry and around window frames and window sills. It can often occur in bathrooms or behind leaking appliances.
If you do notice signs of fungal decay, the next step is to understand if the problem is wet rot or dry rot, as they share many of the same characteristics. This is where you may require the services of a qualified professional, who can fully assess the extent of the damage, the type of rot, and provide you with long term solutions to prevent it returning.
Common signs of Wet Rot include:
Visible fungal growth - Fungal growth will appear confined near the moisture source, as most wet rot does not spread further.
Nearby source of moisture - You may notice damp patches, leaks, pooling water next to the fungal growth, with external building defects close to where the fungal growth is found.
Darkened spongy timber - Timber that is a darker colour than usual, and can be soft and spongy to the touch.
Cracked crumbly timber - Timber may appear cracked, with paint flaking away.
Shrinking timber - Timber may warp and shrink, meaning noticeable changes to the shape.
Loss of strength - Affected timber may appear bouncy and springy, especially floor boards near walls where joists are rotten.
Wet rot has a distinct damp, earthy and musty smell, which can be similar to decaying vegetation. The wet rot smell comes from the fungi breaking down the structure of the timber, which releases organic compounds. This may be similar to the smells of decaying leaves when you take a walk in woodland.
If you notice a damp smell in your property this could indicate a problem with moisture ingress, and wet rot. It is crucial to investigate for any visual cues in order to discover the source of the smell.
If you are concerned about a wet rot problem in your property, or if you are unsure if a fungal decay problem is wet rot or dry rot, you may require professional assistance.
Sometimes small isolated areas of wet rot, such as on an external window sill, may only require DIY treatments, but for extensive problems affecting structural timber, a CSRT or CSTDB qualified surveyor should be consulted.
It is essential that you stop the source of moisture causing the problem, otherwise the problem will return, while professional wet rot wood treatment is always recommended for effective and long-lasting results.
A qualified surveyor is able to fully investigate your property, identify the source of damp problem causing the fungal decay outbreak, check the condition of timber and the extent of any damage. Timber decay is often hidden underneath floorboards in the sub floor void, behind panelling or in roof spaces.
The surveyor will detail their findings in a survey report, laid out in an easy to understand manner, with recommendations for treatments, if required. The surveyor will be on hand to answer any questions you may have.
Our surveyors have extensive experience dealing with all types of properties, meaning they understand the architecture of buildings local to you, and can correctly identify damp and timber problems to strict industry standards. We can provide extensive advice and solutions for domestic home owners, commercial clients, social housing providers and for listed or historic properties across the UK.
If a surveyor identifies wet rot during their survey of your property, and you wish to go ahead, our experienced technicians will carry out remedial wet rot treatments to remove the wet rot and prevent its return.
We have local technicians who are skilled in joinery and will carry out repairs to the highest industry standards. They will talk you through the process from start to finish, while ensuring that you face minimal disruption. Our technicians are equipped with protective floor coverings, Hilti dust extraction units and vacuums in order to keep your property clean and tidy.
Rentokil Property Care has been working in peoples homes and businesses for over 70 years, correctly identifying property issues and providing long term solutions.
We are experts in property preservation, and can provide you with personalised advice for wet rot problems affecting your property.
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