TIMBER – DRY ROT

All wood rotting fungi are the result of timbers being kept in contact with persistent dampness.

"Dry rot" is the term used for decay caused by Serpula lacrymans, the True Dry Rot Fungus. It is a brown rot that destroys the cellulose component of wood, eventually reducing timber to a dry and crumbly consistency.

It is the most serious type of timber decay in buildings because it can cause rot at a lower moisture content than wet rot fungi and it has the ability to grow through damp masonry, brickwork, and behind plaster. It can therefore spread rapidly through a building, making treatment both complicated and expensive.

Left untreated it can destroy in months what the equally determined wood-boring insect larvae may take years to achieve. Caused often by a combination of dampness and insufficient ventilation it results from such causes as defective gutters, roof faults, blocked under floor air vents, bad pointing and rendering, the lack of an effective damp proof course, or the sealing of any space into which moisture has access. It is a primitive form of vegetable life that derives its nourishment from timber by destroying the cellulose thereby depriving the wood of all its natural strength.

Once established, it grows rapidly by pushing out fungal strands (hyphae) even through thick masonry in its search for more timber on which to feed. Dry rot will grow sheets of a substance known as mycelium which is foul smelling. From this, fruiting bodies (sporophores) may eventually form, producing millions of airborne spores which carry the infection elsewhere, not only throughout the building but to other buildings where conditions for germination occur now or in the future.

Dry rot is a malignant destroyer that can remove all the strength from buildings and has been responsible for their complete collapse on occasions when it has been permitted to go unchecked. With any fungal decay it is important to bear in mind that, like an iceberg, what a property owner has seen might only be the tip of the problem.

DON’T WORRY – It can be fixed!

Four principles should be recognised and applied when dealing with any form of fungal decay of timber in buildings:

• Identify and remedy the fault that permitted entry of dampness into the building
• Dry out the existing dampness
• Remove the fungal growth and repair the damage caused
• Isolate or treat timbers at risk from continuing dampness with a protective fungicide.

These principles have remained unchanged for many years. However, with continuing research on treatment techniques, the type of fungicide, the quantity required and the method of application have improved significantly over the years. This benefits the property owner, the user and the environment.

Building Maintenance Control has over a decade of experience in the eradication of both wet and dry rot. Our fully trained and experienced surveyors will identify the type, and the extent, of any decay and will produce a suitable specification for the eradication of the problem. You will also have the peace of mind from a 30 year guarantee for the work carried out.

When our surveyor identifies dry rot in a part of your property, he may eventually need to have some exposure work carried out, such as the lifting of floorboards to enable him to ascertain the fullest extent of any fungal attack.

This is an important consideration and property owners should ‘beware the company’ that gives recommendations or quotations based solely on a relatively superficial inspection of any fungal problem.

Where our qualified surveyor deems it necessary to use fungicides to treat dry rot, the chemicals, which are usually water based and contain extremely low concentrates of active ingredients, are applied only to those areas of wall fabric or at risk timbers identified by the surveyor. There are a variety of methods by which this can be achieved, but the type of solution and method of application depend upon the type and extent of decay and the extent of structural deterioration to colonized timber.

Once the rot has been treated, it is important to consider the extent of damage caused by the fungus. Since the fungus breaks down the timber in order to survive, the important question is whether a timber has enough residual strength that it can still perform the purpose for which it was designed. Where a timber has been significantly damaged it is then necessary to turn attention to repairing its structural deficiency. If damage is overwhelming then the entire timber may have to be replaced. Where one end or part of a timber has been damaged it is possible to cut back to sound wood and replace the damaged part. Repairs to substantial structural timbers which are plainly visible present an interesting challenge in ensuring that the repaired timbers continue to blend into the surrounding architectural features.

In the past, substantial steel plates, bolts and timber connectors would provide a structurally satisfactory repair but often resulted in an eyesore of significant proportions that would draw attention to the repair itself rather than the attractive surrounding architectural features.

Modern techniques, particularly the use of epoxy resin, has revolutionized the repair of structural timbers, at least aesthetically. These repairs allow virtually any type of repair to be carried out with no visual evidence of the repair. These repairs can be carried out entirely in-situ or can be factory prepared.