All forms of wood rotting fungi require moisture in order to thrive. Provided that timber is kept dry it will not decay. It is important to have a wet and dry rot treatment and prevention  strategy, because once untreated timber is allowed to become damp and to remain in that condition, it can be attacked by one or more of the many species of wood rotting fungi. The terms ‘wet rot’ and ‘dry rot’ are commonly used to describe fungal attack to timbers in buildings.

Whilst these terms are not precise scientific classifications they serve as a convenient way to differentiate between Serpula Lacrymans, the true DRY ROT FUNGUS, and other forms of fungal decay of timber which can be referred to collectively as WET ROT.

Accurate identification of the species responsible for decay is essential to ensure that the correct treatment is specified and the subsequent eradication of the rot achieved.

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The true dry rot is probably the most serious of all wood destroying organisms encountered in Ireland and the treatment normally necessary is far more extensive than that required to deal with an attack by any one of the wet rot fungi. There is only one dry rot fungus in Ireland and in the UK.

This is the true dry rot which lives on the cellulose of damp timber. To decay timber, dry rot requires a minimum moisture content of 20% usually in conjunction with moist, warm, windstill conditions. This will spread most rapidly on timbers with a moisture content of 30% – 40%. It draws moisture out of the timber it attacks, causing the timber to lose weight and consequently to become friable and cuboidal in appearance.

The fungus threads can carry the moisture to adjacent drier timber which is subsequently attacked. Once established it can, in poorly ventilated areas, affect the moisture content of timber to create conditions for its continued growth.

Apart from growing over timber, dry rot can spread across and through brickwork and masonry in search of new timber to attack. It’s rate of growth can be extremely fast (up to 150mm in a month) which can cause extensive damage to a property in a very short space of time.

Under ideal growing conditions, the fungus will fruitify in summer after some three to four years producing a fleshy white fruit body from which millions of red rusty seeds or spores are discharged. The attack is usually due to faulty construction or lack of maintenance. A statistical analysis carried out by Pro-Tech over a 10 year period revealed that 78% of dry rot attacks were caused by rainwater penetration as a result of structural defects or lack of maintenance.


A purely visual inspection of the accessible timbers is seldom sufficient. In most buildings there are timbers built into the walls or concealed in other ways and such timbers cannot be inspected without considerable exploration. A diagnostic inspection which considers the visual evidence of decay, the cause of the problem and pattern of moisture ingress, the construction of the building and in particular the probability of concealed timbers, can highlight the suspect areas.

Thereafter, these areas must be opened up in order that the full extent of the rot can be established. It is imperative that inspections are only undertaken by fully qualified surveyors.

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Pioneering Approaches to Solve Your Wet Rot/Dry Rot Problems

The treatment of dry rot invariably involves considerably more work than the simple spraying of timber with a wood preservative. To eradicate an attack by the true dry rot fungus and to provide long lasting protection against reinfestation requires a comprehensive scheme of chemical treatment and a carefully detailed programme of associated building work.

Treatment is extended in all directions from areas of known infestation, the extent of the treatment being governed by the detectable growth of the fungus and the pattern of moisture present which could support the spread of the attack. The treatment resulting from this three dimensional approach can be likened to the formation of a ‘toxic box’ within which timbers are protected both chemically and physically. Brickwork, masonry and oversites are sterilised and deep toxic barriers are set up to ensure that any deep seated fungal growth is contained.

Note: It is essential that the building work should include the rectification of the ingress of moisture responsible for the attack and replacement of any structurally weakened timber with treated timber. Thereafter all potential sources of moisture must be inspected regularly to ensure that the fabric of the building is maintained in a dry and weatherproof condition.

The treatment of wet rot is usually less extensive than that required to eradicate an attack by the true dry rot. Any existing timbers that are structurally weakened must be renewed and the replacement timbers treated.

Treatment should also be extended to timbers in adjoining areas in which the level of moisture is sufficient to support fungal attack. In most cases the extensive sterilisation of walls associated with dry rot treatment is not necessary.

As in the case of dry rot, sources of moisture must be rectified and structurally weakened timbers replaced.

Pro-Tech will identify the problem and recommend the appropriate remedial treatment. The company will provide experienced personnel and equipment to carry out the work essential for a successful cure. Equally important, this treatment will give lasting protection to ensure that there is no recurrence of the problem, provided that all sources of moisture are eliminated.

Eradication is carried out under our twenty year written guarantee, excluding only treatment of joinery items and furniture.

There are many fungal species that are collectively known as wet rot. In general, wet rot is more localised than dry rot, and requires a sustained higher moisture content. Damage is contained within the affected timbers since the fungus cannot penetrate brickwork or masonry.

This most common of the wet rot fungi which is sometimes called Cellar Fungus, feeds on damp timber and causes the wood to lose weight, strength and ultimately to collapse.

The fungus has the power to send out strands (hyphae) to spread the attack to other damp parts of the building in the same manner as the dry rot fungus Serpula Lacrymans, but it requires much more moisture and is therefore considered to be a ‘local’ fungus.

A report is submitted, clearly setting out the type and extent of the decay found, and a full specification for the remedial work required, together with a cost for the remedial treatment.