Remedial timber treatment and damp proofing companies typically recommend stripping out of building fabric beyond the visible extent of the infestation and the use of fungicide.
This particular species poses the greatest threat to buildings since it can spread through non-nutrient providing materials (e.g., masonry and plaster) for several meters until it finds more timber to attack.
Environmental conditions for mycelial growth following germination[2] The average moisture content of modern softwood timbers in dry buildings is generally in the range of 12–15%,[2] and heating systems may reduce this to a far lower level.
A fruiting body (sporophore) may develop naturally or in response to unfavourable conditions of humidity, temperature or exhaustion of nutrients.
Laboratory experiments conducted in 1932 on timber samples in unventilated glass jars showed that significant quantities of water were indeed produced.
However these experiments do not replicate the "real world" environment of a building where processes of evaporation and capillary action in the wood will be removing moisture from the area faster than it can be produced by the fungus.
[6] While the mycelium strands do conduct a nutrient solution around the fungus, it has been shown that any ability to transport water to "wet up" dry timber is very limited.
[1] The first step in any course of treatment is to make the necessary repairs to the building defects (overflowing gutters, blocked airbricks, missing slates, etc.)
The following description for the treatment of dry rot is typical of traditional methods:[7] As can be seen from stages 1 and 2, this involves the removal of a considerable quantity of building fabric.
The desire to kill the fungal strands within all materials adjoining the affected timber has led to the practice of "wall irrigation" at stage 4.
[citation needed] Glycol and boron solutions are hydrophilic (water-loving) and react with the water in wood, making it unavailable for the fungus.
Recipes for homemade fungicide solutions, wood hardeners and penetrating epoxies have been reported on the web in addition to commercially available products.
Even when the ingress of water has been stopped and good ventilation established, it will take a considerable length of time for the wall to dry out.
"[2] The environmental approach emphasises the need for continued monitoring to ensure that future building defects do not start a new outbreak of dry rot or reactivate a dormant one.
The use of a blowlamp to kill dry rot by applying heat to the surface of affected areas was popular at one time.
[2] In Denmark, a procedure has been developed whereby the building, or the affected part thereof, is tented and heated by hot air to kill dry rot.
However, the question could be asked as to why someone should expend large amounts of energy heating the entire building to a high temperature when all that is needed to kill the rot is to dry it out.
[14] A further possible way of combating dry rot is by the use of antagonistic organisms that reduce the ability of the decay fungus to colonise or degrade the wood.
[15] Field trials have also been carried out investigating the ability of Trichoderma fungi to prevent rot in electrical distribution poles, with mixed results.
One argument put forward by the supporters of the environmental approach concerns the potential effect on human health of the large quantities of toxic chemicals used in orthodox treatments.
Typical quotations are: "chemical control methods cause extensive environmental degradation, pose potential hazards to wildlife and are of grave concern to public health bodies"[12] and "many cases of illness including headaches, respiratory problems and chest pains, to name a few, have been linked to the use of such agents within buildings.
Generally, the toxicity of the fungicides used by the industry has been reduced since 1991 with chemicals such as dieldrin, pentachlorophenol, and tributyltin oxide being replaced by organo-boron esters, permethrin, and boron/glycol mixes.
[9] Some evidence has been produced recently that workers exposed to high levels of solvents over a number of years may develop damage to the central nervous system, but the studies have not been conclusive.
[9] However, in the UK at least, this is a major consideration, as bats are protected under the Wildlife and Countryside Act 1981, which states that harming them or disturbing their roosts is a criminal offence.
[22] The full results are published in a research report by Historic Scotland[1] and conclusively show how the growth of dry rot can be controlled simply by varying the available moisture in the environment.
A case study of successful environmental control of dry rot in a large building is included as an appendix in Historic Scotland's "Technical Advice Note 24".
The 20-year guarantee issued by the treatment company had a clause that excluded liability if recurrence was due to "a failure to keep the property in a dry and weatherproof condition and in a good and proper state of maintenance".
The UK Court of Appeal held that the guarantee was not invalidated by this clause because the wall into which the timber was built was damp due to the nature of the construction of the building, not through any lapse in maintenance by the owners.
Graham Coleman, a leading specialist in damp treatment and timber decay, makes the same point on his website: But then dry wood doesn't rot – so what is actually being 'guaranteed?
In fact, guarantees for chemical dry rot treatments may be harmful as they may lure the building owners into a false sense of security by allowing them to feel that they can afford to be less diligent with property maintenance.