Causes †
* Defective construction, e.g. broken roof tiles; no damp-proof
course.
* Installation of wet timber during construction, e.g. framing
sealed behind plasterboard linings; wet joists under floor
decking.
* Lack of ventilation, e.g. blocked air bricks to suspended timber
ground floor; condensation in unventilated roof spaces.
* Defective water services, e.g. undetected leaks on internal
pipework; blocked or broken rainwater pipes and guttering.General treatment †
* Remove source of dampness.
* Allow affected area to dry.
* Remove and burn all affected timber and sound timber within
500 mm of fungal attack.
* Remove contaminated plaster and rake out adjacent mortar
joints to masonry.
Note: This is normally sufficient treatment where wet rot is
identified. However, where dry rot is apparent the following
additional treatment is necessary:
* Sterilise surface of concrete and masonry.
Heat with a blow torch until the surface is too hot to touch.
Apply a proprietary fungicide† generously to warm surface.
Irrigate badly affected masonry and floors, i.e. provide 12 mm
diameter bore holes at about 500 mm spacing and flood or
pressure inject with fungicide.
† 20:1 dilution of water and sodium pentachlorophenate, sodium
orthophenylphate or mercuric chloride. Product manufacturers'
safety in handling and use measures must be observed when
applying these chemicals.
Replacement work should ensure that new timbers are pressure
impregnated with a preservative. Cement and sand mixes for
rendering, plastering and screeds should contain a zinc oxychloride
fungicide.Further reading †
BRE: Timber pack (ref. AP 265) † various Digests, Information
Papers, Good Repair Guides and Good Building Guides.
In-situ timber treatment using timber preservatives † HSE Books.Ref: Bldg. Regs. Approved Document C, Site preparation and
resistance to contaminants and moisture.Timber Rot---Causes, Treatment and Preservation