Dry Rot
Dry Rot and Wet Rot both require the same minimum moisture levels to develop decay in affected timber.
However Dry Rot, unlike Wet Rot, can grow into the masonry and plasters and indeed travel through the fine cavities / capillaries and joints especially in areas where damp is continuous, i.e. poorly ventilated or drained areas or walls where penetrating damp is saturating.
Treatment must always begin with drying the structure prior to remedial repairs and treatments.
Dry Rot requires thorough investigation to areas surrounding the decay and a full scheme for prevention of future outbreaks.
MISCONCEPTIONS ABOUT DRY ROT AND MOISTURE
Dry rot can transport its own water sufficiently to cause extensive spread to drier parts of a building.
Although the strands and mycelia of dry rot can transport water, their capacity to do this is limited. The fungus can only spread from damp areas into adjacent areas where ventilation is so restricted that the transported moisture can build up and promote decay in the wetted timbers. Gloss paints and other impervious coatings on masonry or stud walls act as barriers to water vapour, and may allow the fungus to dampen the underlying wall and so enable it to spread.
Dry rot can remain dormant for many years and then suddenly induce a new outbreak.
Dry rot mycelia and strands can remain in active in dry timber for many years before finally dying, especially under cooler conditions such as in cellars. However, only if damp conditions return, exceeding 22% moisture content, will the fungus become sufficiently active for significant spread to occur; for example, where untreated timber of low natural durability remains in contact with either infected timber or masonry containing infected timber fragments. Although dry rot can survive in a dormant state in dry masonry for some time, it is not known for how long.
MISCONCEPTIONS ABOUT TREATMENT OF DRY ROT
Effective dry rot control requires all infected timbers to be removed and all infected masonry to be sterilised.
Although removal or sterilisation of infected material would in theory achieve control, in practice it is often impossible to identify precisely all infection and impracticable to remove or sterilise all affected material. The essence of effective control is the prompt restoration and future maintenance of dry conditions.
Infected and decayed wood removed from a building should be treated with preservative or burnt on site.
As a matter of good practice infected timber should be removed from any building with damp conditions. However, once removed it can be temporarily and safely stored outside on site provided that it is not adjacent to the walls of any buildings. Disposal to a local authority side poses no hazards, although contamination of hardcore with decayed wood can lead to decay problems in new construction. Treated wood might be regarded by local authorities as toxic waste and unauthorised disposal to a landfill site therefore could be illegal. Burning infected, untreated timber on site is common practice but it is not necessary as a means of removing any decay risk to existing buildings.
Dry rot spores on oversites beneath suspended timber ground floors must be sterilised by spraying with dry rot masonry fluid.
Dry rot spores on an oversite cannot result in the spread of the fungus unless timber, card or paper debris are present on or in the oversite. If such debris is present in an infected building, it may well already be infected and must be removed. Surface spraying of the oversite is unlikely to prevent the spread of fungus from infected debris and, except under unusual circumstances, is unlikely to be justifiable as a result of a COSHH assessment.
We are well located to serve the midlands, west country, and mid and South Wales
 
|