Timber decay such as dry rot and wet rot can affect buildings of all ages. Unless these are properly identified and urgent remedial action is taken, the condition and value of your property can take a nosedive.

Fungal decay occurs in building timber that has been wet for some time, creating the right conditions for wood-destroying fungi to thrive. The best-known species are Serpula lacrymans (dry rot fungus), Coniophora puteana and Poria vaillantii (wet rot fungi). Dry rot is the most serious form of fungal attack in a building, since it can spread and destroy much of the timber. The consequences of a wet rot fungal attack tend to be less serious since the decay typically remains local.

While all types of wood rot behave in the same way when an outbreak occurs, there are significant differences between wet rot and dry rot. Wet rot fungi require a higher level of moisture for growth to take place compared to dry rot which thrives in environments with a moisture content of 20-30%.

Understanding dry rot

Serpula lacrymans aka dry rot or brown rot develops quickly on the surface of infected timber in still, humid conditions where it produces a mass of cotton wool-like growth (mycelium), often with water droplets present on the surface. The continued growth of the delicate hyphal threads over time supply water and nutrients to the fruiting bodies, spreading onto adjacent stone or brick walls in search of more timber. Mortar joints, plaster layers and areas of damp wall can easily become infected.

Dry rot can lead to any and all internal and external wooden structures to become vulnerable to decay and destruction. An attack leaves the timber weak and brittle, with a poor appearance. It can also be expensive to remedy. Due to the low moisture content required, dry rot can spread easily around the house, so the key action to take is to remove the source of moisture. If you’re not sure whether dry rot is present in your home, there are various way you can identify its existence, including:

• Sinking or shrinking areas of timber, particularly around skirting boards

• Characteristic cuboid cracking and darkening timber

• Fungal areas that resemble cotton wool, sometimes with water droplets on the surface

• Mushroom-like growths (fruiting bodies) in silver/grey shades, often with yellow/purple patches

It cannot be stressed enough that if dry rot is detected within your property, swift action must be taken to tackle the issue and prevent the fungus from spreading and causing more damage.

Understanding wet rot

Wet rot is primarily caused by Coniophora puteana or Poria vaillantii and it tends to stay in the area of dampness where it develops rather than spreading around. Any timber that is exposed to large amounts of continuous moisture constitutes an ideal breeding ground for the fungus. If you have leaky roof, gutter or bath problems, excessive condensation, burst pipes or penetrating damp, you need to take action to prevent the onset of timber decay caused by wet rot.

Identifying wet rot in your home is not as straightforward as you may think since its appearance can vary. However, do look out for:

• A characteristic damp, musty smell

• Timber shrinkage and sinking

• Soft, spongy areas of wood, particularly around window frames and sills, door frames and skirting boards

• A cracked appearance and a darker colour

• Visible fungal growth

Again, if you detect signs of wet rot in your home, it is available to act quickly to remedy the problem in order to maintain the condition and value of your property.

What to do if your home is affected?

As shown above, the first step is to correctly identify the type of fungal decay taking place. Commission a detailed diagnostic inspection by a specialist surveyor or damp & timber decay specialist to get the full picture in a report that should detail both the cause of the problems and any proposed remedial action.

In cases of wet rot, treatment is often no more serious than applying a fungicide to the affected timber, and in extreme cases the timber will need replacing. The cost of treatment depends on the severity of the problem. Replacing timbers can be costly.

Dry rot treatment starts with finding the source of the moisture and fix the fault, then laying bare the full extent of the spread, which may well involve removing plaster and render in all directions in addition to removing flooring. Once the infected timbers have been identified, they need cutting back to at least 500mm beyond the last signs of fungal growth. Clean up all evidence of fungal growth and replace the timber with pre-treated timber that has been impregnated with dry rot fungicide. You should also sterilise the brickwork. For badly affected properties, be warned, costs can run into many thousands.

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