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Dry rot Guarantees - any practical value?

If you have a chemical damp-proof course installed and it proves not to be effective then it will be rectified under the terms of the guarantee.

If woodworm emerge following treatment then it will also be rectified under the terms of the guarantee.

So if dry rot returns after chemical treatment it will also be attended to under the guarantee. Right? Wrong - or it appears to be so.

In the case of dry rot, Serpula lacrymans, or indeed any rot, there are frequently building works eg. removal of rotting/rotted wood and reinstatement of timbers; there is also likely treatment with fungicide to both timbers and in the case of dry rot, to walls. However, the major condition of the guarantee is that it will only remain valid if the property is well maintained, in other words kept dry. But then dry wood doesn't rot - so what is actually being "guaranteed"? Certainly not any chemical treatment that has been applied since it is clearly implied that if treated timber becomes damp it will rot. So what was the value of the preservative treatment? Obviously none! So what is the point of it if it can't meet its requirements of preservation against rot?

When the question was put to the British Wood Preserving and Damp-proofing Association and the Guarantee Protection Trust (GPT) we were politely told that such insitu preservative treatments are only guaranteed for the "drying out period". This is rather odd for several reasons:

1. I have never seen a guarantee relating to rot where insitu preservatives have been used which states that they (preservatives) have an effective life of the drying down period only.

2. Such statements are not covered in the reports and covering documents and are therefore unlikely to form part of the contract.

3. How long is the drying period - hours, days, weeks or even over a year or two? You may as well ask how long is a piece of string. Again, such information is not present in reports I have seen. Indeed imagine two identical scenarios, one where drying down takes a few weeks and another where it takes over a year. Both have received the same chemical treatment yet in one case the treatment is only expected to be effective for a few weeks and in the other for over a year. But what if the treated timbers under the conditions of the shorter drying period were subject to further dampness after, say, six months? According to our given logic it would have been expected to fail as it was outside the drying period, ie, after a few weeks; yet in the second scenario it would still be expected to be effective at this time because this drying period is going to be over a year, ie, the timbers are still damp. Perhaps any 'damp' that occurs on rewetting is a different 'damp' to that which is present during the drying down??!! Perhaps someone could explain - or are we being too cynical. There clearly are questions relating to the logic of the drying out period argument.

There is one final consideration with reference to rot, especially dry rot. If timbers have become damp and rotted due to water ingress and work is carried out with the usual guarantee clause stating that the building must be kept dry, etc, for the length of the guarantee period (20-30 years), is it reasonable to expect that a property will never let water in again over this period, especially the older housing stock?

The answer is probably that such an expectation is unreasonable.

In many cases the cause of water ingress is not readily identifiable, or at least only after the rot is discovered: it is the rot that draws the attention to the water ingress. How many rotted embedded lintels are present in older properties only to be found, say, during renovation works? There was, in many cases, no internal evidence of water ingress or apparent external defects to indicate that water may be entering and causing the rot. Indeed, in one recent case following the discovery of dry rot, work was carried out to eradicate it: the building was re-rendered and finished in a good weather resistant coating. However, four years later rampant dry rot was discovered. There was no external evidence of obvious defects and no internal evidence of dampness other than when a fruiting body suddenly appeared on the skirting. Examination showed the dry rot to be due to water penetration via very minute cracks in the finishing coat on the south-west wall (faced prevailing winds). It was only after the discovery of the dry rot that very close examination revealed these minute cracks.

So when undertaking work in old buildings in relation to rot it is not unreasonable to expect that within the life of the issued guarantee water ingress may again occur unbeknown to the owner. Therefore, it is incumbent on those undertaking repairs, etc, to allow for such a possibility. Thus timbers should be replaced in such a manner that if water ingress does occur again (other than plumbing leaks) then rot cannot occur; basically it is Good Building Practice.

Finally, when those who remarked that the insitu chemical preservative treatment of timber (or walls in the case of dry rot) was only effective under guarantee during the drying down period, were asked how long this would be, there was a deathly silence. I wonder why?

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