The Hopps Partnership

Wet Rot – How to Identify and Treat


The Hopps Partnership undertake numerous Building Surveys, Homebuyers Reports and Condition Reports each month and come across diverse defects that require careful analysis. This week we had a schedule of condition close to our stomping ground and we came across a case of wet rot, giving the perfect opportunity to write a blog on its identification, causes and treatment.


What is Wet Rot

Wet rot commonly refers to a family of fungus that cause timber to break down in the presence of high moisture levels. Wet rot fungi obtain their nutrition by breaking down the walls of wood cells resulting in a loss of strength of the wood, ultimately leading to structural failure. Wet rot is different to dry rot in that it will not travel past the wet portions of wood or through brickwork and so areas most commonly affected are beneath leaking pipes, roofs and under floors.

How to identify Wet Rot

Wet rot fungi generally can be identified by looking for wet, darkened timbers that have become spongy and soft with dark root like structures called hyphae which clump to form mycelium (but it is worth remembering that there are many varieties of wet rot that are all a little different). There may be localised fungus and the area will smell musty. Cracks will eventually occur in the timber and will often follow the grain but can cause a cuboidal pattern as can be seen below. Cuboidal cracking pattern in timber Fruiting bodies (mushrooms) are less common where there is a constant source of moisture but occur when the conditions change such as when moisture levels decrease or the source of nutrition reduces as the timber further decays. The mushrooms create spores that spread and may lay dormant until conditions are right once again for further growth. Wet rot can be identified outside the property on wooden cills or most commonly inside the home in enclosed hard to reach areas such as; under floorboards, behind skirting boards, in joist ends which sit in wet walls and in rafters where a roof may be leaking. As these areas are not often checked the rot can be left untreated causing it to become soft and brittle when dry and ultimately once the timber reaches a critical stage of decomposition, total replacement is required. Wet rot is found in timbers that on testing have a moisture content of over 25% but depending on the type of fungus, moisture content of over 40% may be required. Rotten timber in a window frame A rotten joist end bedded directly into brickwork

How to Treat Wet Rot

The main priority is to stop the source of moisture and dry out any affected areas, a process of controlling the environment. It is therefore important to stop all leaks and sources of moisture which may mean fixing a roof, replacing pipework or a leaking toilet and sink traps or ventilating areas that have become damp through condensation. Once identified if the timbers are badly affected, it will be necessary to replace them with treated timber to British Standard BS 5268. If it is necessary to place timbers back into areas that are not fully dry, it may be necessary to wrap the timber ends in thick polythene to isolate them from the moisture. If the timber is mildly affected it can be repaired (typically in non-structural timber such as window cills). It should be possible to dry out the affected areas and then use a timber hardening resin. The resin will strengthen the affected timber and give a good base for decorating over but should not be considered as a structural alternative in floor and roof timber. If you have a question or feel that you have identified wet rot, please give our Charted Surveyors a call and we will be happy to assist.


Posted by: Robert Hopps

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