Dry Rot: Not your average type of rot

Background

Dry rot is the decay due to specific strains of fungi, the most common of which in the UK is known as Serpula Lacrymans, causing the deterioration of timber in buildings. Unlike other more common forms of rot, it is able to spread quickly and not only into surrounding timber but can also pass through other building materials such as masonry to find a timber source. Often known as brown rot decay, infected wood appears darker than normal and takes on a brittle form that develops cracks, often not only along the grain but also across it giving a ‘cuboidal’ effect. The wood will crumble when pressure is applied.

Occurrence and damage

Despite the slightly misleading name, dry rot requires a degree of moisture within the locality, but as little as 20% moisture content within timber can still see it thrive and spread. The name dry rot is thought to have been attached to the problem as wood affected by it often appears to be dry on initial inspection.

Dry rot can attack both hard and soft woods meaning it is able to cause damage to almost any type of timber structure and an outbreak is an extremely serious infestation. It can cause significant structural damage and if untreated, the decay can eventually cause instability, and in particularly prevalent cases cause the structure to collapse.

Early identification and treatment is essential to minimise damage as the spread of the problem can occur over the course of weeks and months rather than years and decades.

Due to the low level of moisture that the fungi needs to survive and develop the cause of the dampness in the vicinity is often difficult to pin down. Common reasons include minor common plumbing defects, leaks or condensation, as well as rising dampness, poor ventilation or poorly protected exterior walls.

Eradication and rectification

Identifying the source of the moisture will be the immediate priority once dry rot has been found. The removal of this nourishment will stifle the fungi and bring an immediate halt to the spread of the problem. However, the low level of moisture required along with the location of the timber often means that the timber may not remain dry in the longer term. For this reason a number of other strategies are available that will offer more certainty that the fungi has been completely eradicated.

The strategy will depend on the extent of the problem and will range from simply treating the area with chemical fungicides and monitoring the affected timber; to cutting out the decayed wood along with surrounding building materials, cleaning and treating the area with fungicides, and replacing the wood with preservative-treated timber.

This is specialist work. Not only in terms of correctly identifying this type of rot so that the appropriate remediation works can be planned, but also any associated work must be project managed and undertaken by suitable experts. There are contractors who work solely in the field of making good problems with dry rot and, as always, references should be sought along with guarantees for the work.  A strong track record is more important in this case that ever, as should the work be undertaken incorrectly and the rot returns the process will need repeating.

Finnegan Associates is a practice of Chartered Building Surveyors with extensive experience of identifying building defects such as dry rot, as well as scheduling and project managing remedial work.  If you would like to discuss any of the issues covered in this blog contact info@finneganassociates.com or call 020 3137 8078.

A final thought

Whilst Finnegan Property Services cannot claim to have experience in the nautical field, a brief example that clearly demonstrates the potential damage that dry rot can cause, as well the potential cost if not identified and treated early, can be found in our history on the high seas.

The second HMS Queen Charlotte was built shortly after the battle of Trafalgar and launched to great acclaim in 1810. Shortly afterwards the timbers of the upper decks were found to be infected with ‘dry rot’ and by 1816 the cost of remedial work had amounted to £94,499 – an incredible sum at that point in time, which even exceeded the original cost to build the ship which stood at £88,837.

Posted on 2 October, 2015

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