Yorkshire Dampcourse home page :: Wet and Dry Rot

Wet and Dry Rot

The ingredients for rot to start in timbers are timber, fungal spores and water.

Excluding any one of these from the 'mix' prevents rot from occurring. In properties there are many timbers and spores everywhere; this leaves the one controllable ingredient as water. Unfortunately we place many timbers in areas of buildings where they are susceptible to moisture ingress. This is particularly so in ground floors, roofs and in areas where we use water, such as bathrooms and kitchens. Any timbers that come in prolonged contact with water will eventually rot.

Wet Rot

Wet rot in floorboards

Where spores can germinate the usual result is decay to timber by wet rot. This is a localised fungal infection only to those areas of the timber that are damp. Wet rots are not aggressive fungi and will die when moisture is removed from their environment. Treatments for wet rot usually rely on physical exclusion of moisture and the removal and replacement of decayed timbers. Chemical treatments are not usually required, but are employed to provide protection to new timber materials or where fungal growth has been particularly heavy. They would also be used as a stop-gap measure if a rotted, but still serviceable, timber had to remain in place.



Dry Rot

Serpula-lacrymans - dry rot

A different more aggressive fungal attack is that of dry rot. This always starts in wet timbers, but can continue to grow with a restricted moisture supply, spreading extensively through masonry to attack any timbers it meets. Severe structural damage to timbers in buildings can result and specialist treatments are always required.





Like assessing insect attack to timbers, our work to deal with timber rot always starts with a visit to site to inspect the problem. Testing usually involves the probing of potentially affected timbers with a sharp screw driver and visual identification of any fungal growths. Any "give" in the timbers indicates softening usually caused by fungal decay. In well decayed timbers a screw driver can be driven into the rotten timber core, or sections of timber easily split away from the timber's surface. Treatment depends on the rot type, its location and the structural requirements of the remedial repairs. The initial treatment must always allow for the exclusion of water from the timber, or the isolation of the timber from further moisture source with a physical barrier. Chemical treatments are employed to help new timbers or remaining timbers withstand levels of residual moisture, which otherwise might continue to allow further decay. 


Use of fungicidal treatments is governed by Acts of Parliament (law) and Health and Safety Regulations. This requires specialist knowledge. Timber replacement must follow existing Building Regulations and guidelines to make sure that the timbers can perform structurally to specification.

Where treatment is recommended/required, then this is usually a combination of liquid and paste or gel compounds of boron (a naturally occurring mineral). We also sometimes use a fungicidal micro-emulsifiable solution (FMEC), otherwise known as polyphase or iodo-propynyl butyl carbamate, where circumstances allow or dictate. However, most of the treatments we carry out are with boron, which is a natural fungicide in the right concentration.

Treatments for wet and especially dry rot attack are not straight forward as they may involve extensive rebuilding of structural building components. After treatments Health and Safety regulations require the minimum of 8 hours to elapse and surfaces to be dry before re-entry to a treated area and its reinstatement to habitable use. There are a some fungicides now available where a 1 hour re-entry has been granted, but this is still dependant on the timber being dry as well. Drying out is unlikely to be that fast unless it is forced. We prefer to consider the 8 hour "rule" as being the one to apply.

Recent reformulation of timber treatment fluids now means that they are virtually odour free. Some slight smell may be noticed immediately after treatment, but this quickly declines with drying and improved ventilation.


Dry Rot Dry Rot A very severe attack to sub floor timbers by Serpula lacrymans - dry rot.

Wet or dry rot? Our client asked us to identify the fungal growth in these photos

This site uses Cookies. Info on Cookies. By continuing to browse this site you are agreeing to our use of cookies.

Home Page  Home Page    Member Area   Member Area    Bookmark Page   Bookmark Page    Email a Friend   Email a Friend    Search   Search    Site Map   Site Map   

Terms  Terms    Privacy   Privacy    Feedback Form   Feedback Form    Contact   Contact