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Property professionals see rot on the rise in wet, warm weather

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Property professionals see rot on the rise in wet, warm weather


Published by Anonymous for in Housing and also in Education, Environment, Health

Dry Rot Dry Rot

Property professionals could increasingly come across incidences of wet and dry rot in buildings this year, according to the national trade body The Property Care Association.

A short winter and the deluge of rain in spring, combined with higher temperatures, have all provided a perfect breeding ground for wet and dry rot to thrive.

However, according to the PCA, while the discovery of rotten timbers in a building is a cause of great concern for the property owner – modern technology means this age-old problem can be addressed with an effective solution.

In the past remedial treatment may have required huge structural operations and the mass spraying of chemicals, rendering the building uninhabitable for days and possibly leading to the loss of valuable historical timber and plasterwork.

But over the past ten years or so, there has been a sea change in timber treatment methods, with modern techniques now achieving pinpoint accuracy - and minimal impact on a property and its occupants. 

Steve Hodgson is Chief Executive of the Property Care Association, which represents UK specialists in the remedial preservation sector. He said: “Timber preservation these days means what it says – preservation of as much of the original timbers as possible.

“This means minimum disturbance to building occupiers and to the structure of buildings, not to mention a more sustainable solution with a reduced reliance on chemicals.

“If timber treatment is to rely less heavily on the use of chemicals it is essential that problems with rot are diagnosed accurately in the first place. This is the job of the specialist surveyor.

“Once the existence and extent of a timber problem has been established, the main priority must be to focus on its cause. In cases of wet and dry rot, the source of the problem is excess moisture.

“Broken roof tiles, blocked gutters and leaking water pipes, as well as poor ventilation of timber surfaces, can all be sources of excess moisture and basic property maintenance is often all that is needed to dry out the affected timber.”

Wet rot is caused by wood being in contact with damp masonry. Exposure to high levels of water over long periods leads to a natural breakdown process, seen in all natural organic materials.

Commonly seen on untreated wood exposed to the elements, such as window frames, wet rot will not spread beyond the area of dampness. 

More of a problem is dry rot.  A bit of a misnomer, the term dry rot can be misleading, as a moisture content in excess of 20 per cent is needed before such fungi will develop.

Filaments of dry rot fungus are capable of spreading some considerable distance, over and through masonry, to affect timber away from its original source. However, they can only do this if the masonry or covering plasterwork is damp.

Reducing the moisture content of timber – and surrounding masonry – to less than 20 per cent for cases of rot is therefore fundamental to the long term protection of timber in buildings.

Mr Hodgson added: “There may be cases where it is simply not possible to reduce moisture content to sufficient levels and targeted chemical treatment may be required or prudent – but chemicals should not be a substitute for creating a dry environment where possible.

“Once timber has been dried out, a reassessment should be made in order to determine whether the problem has been eradicated and whether the structural qualities of the wood have been affected, requiring some reinforcement or renewal of the timber.

“In some cases drying out may be all that is needed, with no chemical treatment necessary. Where chemical treatment is needed it should be limited to the affected area. 

“With the very localised treatment of timber these days, where degraded timber needs to be replaced it is usually possible to cut out just the badly damaged portion and splice in a new section of wood.

“Encapsulation of steel rods within the replacement beams can be used to improve the strength of roof trusses. This has been beneficial in the treatment of damaged timber within heritage buildings, causing minimal disturbance to the structure of such properties.”

Of particular note is the fact that the removal of affected timber should be kept to a minimum, particularly in older buildings, as the quality of the original timber is likely to be superior to that widely available today. 

Older timbers – pre-20th century – were originally sourced from ancient woodland from trees some 200 – 300 years old.  Older trees have a higher proportion of heartwood, the dense, infestation and rot resistant wood at the centre of the trunk.

Much of the timber available today is from fast-growing trees from managed woodland that are felled after maybe 50 years of growth.  The proportion of sapwood – that which transports the sap within a tree – is higher and this timber can be more prone to both rot and insect infestation.

So, to conclude, rot or infestation in building timbers need not necessarily sound the death knell for a building or indeed result in the need for large scale structural replacement and treatment.

Modern techniques place emphasis on the preservation of existing timber and minimising the level of structural works – but while we can benefit from advances in technology in this field, it is important to find a specialist that can ensure works are kept on track. 


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