Wet Rot vs Dry Rot — How to Tell the Difference and What to Do
If you’ve spotted something strange or alarming in the timber in your home, whether it’s discolouration, crumbling, or a musty smell, you need to understand what you’re dealing with before it gets worse.
Understanding the difference between wet rot and dry rot can help you know which steps to take. Both are serious issues, and they require different approaches. In this guide, we will cover how to identify each type and what to do next.
Visual Differences: What Does Each Type of Rot Look Like?
If the timber has a dark, soft, spongy appearance, this could be the biggest indicator of wet rot. Other signs include paint bubbling, localised darkening, a musty smell, and the timber feels damp to the touch.
In comparison, dry rot normally has grey or white mycelium strands that are often described as cotton-wool growth. Dry rot also has a distinctive ‘cuboidal’ cracking pattern where the wood breaks into brick-like chunks. It is also accompanied by rust-red spore dust, and can look dry even when the source of damp has been resolved.
Wet Rot:
Dry Rot:
Where Each Type Typically Occurs
Wet rot most often occurs in areas with consistent, localised moisture. Areas like these include window frames, door frames, fascia boards, skirting boards, and subfloor timbers. If these areas are exposed to rising damp, this puts them at significant risk of developing wet rot over time.
Dry rot (also known as Serpula lacrymans) usually originates in poorly ventilated, dark areas like under floorboards, roof voids, and cellars. Most notably, it can spread through plaster, brick and mortar once it has taken hold, making it more difficult to contain.
Causes: What Creates the Right Conditions?
Both types of rot require moisture, but the sources can differ. Wet rot is caused by direct or ongoing moisture, including plumbing issues, roof leaks, condensation build-up, or rising damp. Addressing these issues early is the most effective way to prevent wet rot from taking hold.
Dry rot normally begins in damp conditions – which is typically a 20-30% wood moisture content – but it can spread and persist even if the damp source is fixed. Rising damp is a contributing factor to dry rot, and requires a very thorough treatment to address it and prevent its return.
Which Is More Serious?
Although both are serious issues in their own right, dry rot is generally considered the more concerning type of rot. This is because of its ability to spread through masonry, across walls and into other nearby timbers, even without a continuous moisture source.
Because dry rot can travel through masonry, it is significantly harder to contain and eradicate. In contrast, wet rot tends to remain localised to the source of direct moisture. Regardless, both types cause structural damage without proper intervention, and should not be ignored.
Treatment Differences
When it comes to treating wet rot, the source of moisture should be located and eliminated. This is the best way to begin treatment, because once the source has been addressed, the affected timber can be removed and replaced to restore the affected area. Normally, this treatment does not involve any chemicals, which makes it less costly to resolve.
For dry rot, the source of moisture will be removed and the environment dried out. The infected timbers will then be removed and disposed of before chemical treatment is applied to nearby timber to destroy any remaining fungal growth. Once treatment has been completed, new timber can be installed with physical barriers to isolate them from masonry. Proper ventilation must also be provided to floor voids to ensure airflow and prevent any spores from settling in the wood.
Why Call a PCA-Accredited Specialist?
Both rot types will require an accurate diagnosis as failing to identify it properly can result in incorrect treatment and potentially allow the rot to regrow. Dry rot, especially, can spread invisibly through masonry, which requires a specialist to assess and see what damage has been caused.
Our PCA-accredited specialists follow industry-standard treatment protocols, giving you confidence that the work has been carried out correctly, and recurrence has been prevented.
At Kenwood, we offer timber and damp surveys to assess your home, identifying potential wet or dry rot before the growth escalates. Our solutions cover complete timber replacement and structural restoration for a permanent resolution.
If you’ve spotted signs of rot in your property, don’t leave it to chance. Get in touch with one of our experts today to book a next day survey and eradicate the rot in your home for good.
Frequently Asked Questions
Is wet rot dangerous?
Yes – however, the risk will depend on location and extent. Wet rot weakens the timber, and if left untreated, can compromise the structural integrity of floors, frames, and joists. It is essential to identify and eliminate the moisture source before it can spread.
Can dry rot spread through brickwork?
Yes – this is what makes dry rot more concerning than its wet counterpart. Dry rot (Serpula lacrymans) can spread through masonry, plaster, and mortar to find new sources of timber to infect, which is why professional treatment is essential.
How do I know if I have dry rot or wet rot?
Wet rot is often identified by the way it changes timber, creating a soft, spongy surface. In comparison, dry rot causes cracking in cuboidal shapes that come off in chunks when touched. An accurate diagnosis will require professional inspection, as both rot types can appear similar in early stages as they are triggered by moisture.
What happens if dry rot is left untreated?
If dry rot is left to spread, it will continue to move through walls and into nearby rooms. This may cause progressive structural damage to the timber, making it unsafe and reducing the property’s value. If stopped at an early stage, treatment will be less disruptive and less costly compared to remediation at a later stage.
Does wet rot mean I have a damp problem?
Yes – wet rot is always a sign of an underlying moisture problem. Treatment must address the damp source as well as the affected timber for an effective result.
