Dry Rot vs Wet Rot: what’s the difference?
Finding rot in your home isn’t ideal. As soon as you notice any mushroom-like structures (called hyphae strands) on or around wooden surfaces, it’s time to act.
A home survey can help identify if you have dry rot in your home and recommend the best action to take. This can give you an idea of the cost implications.
So, you’ve found rot in your home. Is it dry rot or wet rot?
Let’s find out.
What is dry rot vs wet rot?
Both dry and wet rot can be extreme hazards for a building. However, dry rot is likely to cause more damage in the long run.
Dry rot usually refers to the fungus Serpula lacrymans – in the rest of the world, there may be a couple of other local species, but not in the UK.
Serpula lacrymans spores float through the air and settle on surfaces of all kinds, including wooden beams, furniture and structural components. When the moisture content of these timbers rises above 20%, it’s ideal germination conditions.
Wet rot, in contrast, refers to a family of fungi and could be one (or more) of a few different kinds. In Britain, the most common species is Coniophora puteana.
It germinates in wood once the moisture content reaches around 50% or higher (much more than dry rot).
What do wet rot and dry rot look like?
Wet rot species look pretty different to dry rot. However, the most significant difference is the texture of the affected wood.
Wet rot leaves the wood feeling spongey and soft. Dry rot removes all the moisture and cellulose, leaving a dry, brittle and weak timber.
Generally speaking, a wet rot fungus might be any colour different from the wood it feeds on. It’s usually white or grey with a dark tinge in the centre, but sometimes it’s dark.
If you can jab a sharp object (like a screwdriver) straight into the affected fungus and wood, it’s a sign that you’re dealing with wet rot. Be extremely careful if this is a structural beam.
Wet rot fungi will also be localised to the water source. It consumes the moisture until there simply isn’t anywhere left to go.
Dry rot, though, is another story. It’s identifiable from the long, wispy hyphae and cotton wool-esque mycelia. The fruiting bodies release reddish spores, and the fungus is generally red or brown with a white layer near the outside.
Because dry rot requires very little moisture to spread, it quickly develops past the original water leak. If you aren’t careful, it can do severe structural damage in a very short period.
What causes dry rot and wet rot?
Wet rot is caused by a severe case of damp. Water gets into the wood, and once it reaches a moisture content of 50% or more, the spores resting there can germinate.
These leaks often penetrate the building from the outside. In other words, you might have a problem with eaves troughs (gutters), downpipes, or a hole in the roof. Continuously and severely leaking pipes would have the same effect.
Dry rot also germinates in damp conditions, but requires much less moisture in the wood (around 20%). This makes it much more of a risk, primarily because it does much more damage.
It’s often impossible to notice dry rot until it’s been spreading for some years, as the problems typically develop in dark areas of a building, like underneath floorboards or inside walls.
The best way to prevent dry or wet rot is to keep on top of damp. Ensure your roof and drainage systems aren’t blocked or leaking. Install adequate ventilation throughout the home (but especially in humid rooms like bathrooms and kitchens).
All these measures should prevent you from needing a dry rot survey at all, keeping your home safe and secure and retaining its value.
Why it’s essential to identify which type of rot you have
Understanding whether you have wet or dry rot is the first step in beginning treatment.
Remember, wet rot generally doesn’t spread as much as dry rot. However, if you find the roof has been leaking for twenty years, it could still be a severe case.
Whether you have dry rot or wet rot, a home survey can help you spot the visible signs and, in some cases, identify how far the fungus has spread and how much damage it’s done. This can helo you decide whether to appoint a specialist to investigate the problem further.
Once identified, both types of rot can be treated with fungicides, but if the problem is widespread, you may need more remedial work to repair the damaged timbers.
GB Home Surveys is a team of chartered surveyors based in the West Midlands, South Wales, and the South West. Our home surveys can be a good starting point for spotting and investigating the first signs of rot, to see if you need expert help.
For more information and a commitment-free chat, feel free to reach out through the form below.
