How to spot dry rot and what to do nextBy: Dakota Murphey
Common sense dictates that you should always have an independent survey carried out before you buy a property. You wouldn’t buy a second hand car without a thorough professional inspection, so why would you take the risk with what could well be your biggest ever financial commitment? Ideally, the building survey will return only minor niggles, giving you the peace of mind that your investment is essentially sound. If serious issues or defects are found, the ‘bad’ survey findings will form the basis of how you proceed with the purchase.
Take the case of dry rot, for example. You would think that a conventional building material such as timber designed to provide structural strength delivers long-term functionality. But as a natural resource, wood is also a vulnerable material that, given the right conditions, can be susceptible to fungal attack – such as dry rot.
What exactly is dry rot?
Dry rot is the common name for a living, growing fungus called Serpula Lacrymans that feeds on timber and, ultimately, destroys wood. It is the most serious form of fungal decay and its presence in a building should send alarm bells ringing. The fungus attacks timbers, digesting the part of the wood that gives it its strength and severely damaging the structural integrity of the affected building.
An important characteristic of dry rot is that it generates moisture through the digestion of timber. In contrast to ‘wet rot’, which typically occurs as a consequence of long-term water ingress or an external leak and tends to be localised around the source of dampness, dry rot can spread without any external source of moisture being present.
If there is any suggestion that the property you are buying could be suffering from dry rot, this will be flagged in red on your RICS survey report, with urgent advice to arrange for further investigation by a timber decay specialist. If you are intending to carry on with the purchase in view of this information, you should commission a dry rot survey to identify the presence of fungal decay, investigate residual timber strength, and outline sensible treatment options and costs.
How does the fungus develop?
Serpula lacrymans spores exist naturally in the atmosphere, but it is only when the right environmental conditions are present that it has a chance to develop and take hold. The perfect habitat for fungal growth is a combination of humidity (20% moisture content, much lower than the 50% required for wet rot) and poor ventilation.
Damp timber that is conducive to dry rot typically occurs as a result of building issues such as rising or penetrating damp, leaking rainwater goods and lack of ventilation. It is important to be aware that these defects may be present in buildings of any age – from nearly-new builds to historic homes. Dry rot commonly thrives in roofs, underfloor areas or behind wall fabrics that have poor ventilation.
There are four characteristic stages in the growth cycle of the dry rot fungus:
- Spores – present in the air, ready to germinate under the right environmental conditions: food (timber), moisture (20%) and air.
- Hyphae – fine white cobweb-like tendrils that grow when spores land on moist timber, acting as channels to extract and transport moisture from timber.
- Mycelium – cotton-wool like substance made from hyphae that spreads away from the original site across timber and even brickwork, in search of new food.
- Sporophore – distinctive, mushroom-like fruiting body with a red centre containing fresh spores that are released to continue the spread of dry rot.
How can you spot the signs of dry rot?
Unless you have specialist knowledge in the field, it can be hard to detect dry rot in a building, particularly when the infestation is in the early stages. However, if you come across some of the following tell-tale signs and symptoms, you should take action straight away.
- Damp, musty, fungal smell
You may well smell dry rot before you see it! A musty odour on its own doesn’t necessarily indicate that dry rot is an issue, but the damp conditions that the smell is indicative of can often lead to dry rot.
- Dark, crumbly wood
Dry rot leaves deep cracks across the grain of the wood. Sections of timber may have a brittle appearance and may have cracked into small cubes. The affected wood may be darker in colour and will crumble due to a lack of structural integrity.
- Fluffy white mycelium
Mycelium growth may be visible across the wood. In addition to the white, cobweb-like coverage, timbers often appear to have a grey ‘skin’, and signs of purple or yellowish tinges or patches may be apparent.
- Fruiting Body
Beyond the timber itself, you may see large flat mushroom-like fruiting bodies, ranging in colour from grey/white to deep orange. Red dust may be spreading from rust coloured centres. Fruiting bodies can easily grow through decorative finishes including paintwork and plaster.
How do you treat dry rot?
It cannot be stressed enough that dry rot is a serious building issue that should never be taken lightly. Left undealt with, the fungus has the potential to cause serious structural damage to your property. While DIY treatments are available for minor outbreaks, serious dry rot problems would always be treated by specialists.
As a potential property buyer, you do have the option of not proceeding with the purchase of any building affected by dry rot. However, if you have your heart set on the building and are willing to engage with the dry rot problem, you should find a competent dry rot and timber specialist to help.
Unfortunately, there are no quick fixes or shortcut solutions, meaning your dry rot contractor will need to provide a comprehensive programme of repair to:
- Locate the source of the moisture that is maintaining the rot
- Repair the defects causing the damp (e.g. damaged gutters, defective render, faulty plumbing)
- Strip out the decayed wood, damaged linings, panellings, skirtings, ceiling wall fabric, flooring etc
- Repair all affected timbers and apply an appropriate fungicide to protect the wood during drying out
- Reinstate walls, floors and ceiling fabric once the full extent of dry rot has been dealt with
- Decorate as necessary.