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What woodworm and rot treatment costs, and when you do not need it
We carry out this work, so we have every commercial reason to tell you that you need it. Here is the honest version instead: a large share of the woodworm and rot we are asked to quote for does not need treating, and the rest costs far less when the diagnosis comes first. This page sets out what actually drives the bill, the ranges quotes tend to fall in, and the questions that separate a fair one from a padded one.
Start with the 215 pound question
A localised survey costs 215 pounds and answers the four things every treatment price depends on: whether the infestation or decay is still active, which fungus or beetle it is, how far it has gone, and what is wetting the timber. Nobody can price the work honestly without those answers, and a quote produced without a survey is a guess dressed as a figure. The most expensive mistake in this trade is not choosing the wrong contractor; it is paying for treatment before anyone has established that treatment is what the building needs.
The survey fee is not deducted from anything and is not a sales visit. If the answer is that nothing needs doing, the report says so, and that is a perfectly normal outcome for us to write.
What drives the bill
Active or historic is the first and largest fork. Beetle needs damp timber, and most of the woodworm in Kent and Sussex houses stopped decades ago when the leak that wet the timber was fixed. Historic activity is a record of an old problem and costs nothing to treat, because it is not treated. Fresh, gritty frass and pale, sharp-edged holes in timber that reads damp are the signs of a live one.
Wet rot or dry rot is the second. Wet rot stays where the water is and ends when the timber dries and the affected piece is replaced, so it is usually a carpentry repair. Dry rot can travel through masonry to reach timber elsewhere, so the extent has to be followed before the scope is set, and that is the outbreak that can turn into a project.
Then the practical questions: how much timber has lost structural section and needs replacing rather than treating, how hard it is to get at, and what the repair to the water source involves. That last one is often the real cost and always the one that matters, because treatment over a live leak is a certificate, not a repair.
Rough figures, honestly hedged
Every job is priced in writing after the survey, so these are ranges to calibrate a quote against rather than a tariff. Replacing a rotten joist end, a sill or a section of floor where wet rot has been confined to one spot is carpentry, and typically lands in the low hundreds to around a thousand pounds depending on access and making good. A targeted woodworm treatment of the floor or roof section that is actually affected, once the moisture is dealt with, is usually a few hundred to the low thousands.
A blanket spray of every timber in the house is commonly quoted at somewhere between one and three thousand pounds, and it is the figure we are most often asked to look at and most often say is unnecessary. A confirmed dry rot outbreak, with opening up, replacement of affected timber and treatment of adjacent masonry, starts in the low thousands and can reach five figures where it has travelled unnoticed for years. On top of any of these sits the repair to whatever let the water in, from a gutter bracket to a rebuilt bay roof.
When you do not need it
Old flight holes with no frass in dry timber. Wet rot where the leak has already been fixed and the timber has kept its strength. A single soft joist end presented as a reason to treat a whole floor. A guarantee offered on treatment over a water source nobody has proposed to repair. Each of these is common, each is quoted for regularly, and each is a case where the right answer is a repair, a repair to the water, or nothing at all.
Our own reports conclude that no treatment is needed often enough that it is a routine outcome rather than a surprise. Where treatment is warranted we carry it out under an insured workmanship guarantee, targeted at the timber that needs it, and where the real job is a gutter, a drain or a ground level we will say that instead.
What to ask anyone who quotes you
Is it active, and what shows that. Which species or fungus it is. What the moisture content of the timber was when it was read. Where the water is coming from, and whether the quote includes fixing that. What happens if you do nothing for a year. A quote that cannot answer these is not a quote for the work your building needs; it is a quote for the work the firm sells.
Questions
Is woodworm treatment ever urgent?
Rarely. Common furniture beetle works slowly, and a floor that has carried an infestation for thirty years will carry it for another season while the cause is established. The exception is structural timber that has already lost section, which is a strength question rather than a beetle question and wants a carpenter. Urgency is a sales tool far more often than it is a fact about the timber.
Do I need a specialist or a carpenter?
Both, sometimes, and often only the second. Replacing decayed timber is carpentry and building repair. Chemical treatment is a specialist job and it is warranted only where activity is confirmed and the moisture has been dealt with. A specialist who quotes chemical treatment for timber that needs replacing is treating the wrong thing, and a carpenter who replaces timber over a live leak will be back.
The mortgage lender has asked for a timber report before they release the money. What do they want?
A written report from a surveyor establishing whether the woodworm or rot noted in the valuation is active, its extent, and what if anything needs doing. A retention is usually released against that report and, where work is needed, evidence that it was done. A survey that concludes the activity is historic is frequently the whole answer, and it is a great deal cheaper than the treatment the valuation implied.
Will home insurance cover it?
Almost never for woodworm or rot themselves, which insurers treat as gradual deterioration. Where the decay was caused by a sudden event that is covered, such as an escape of water from a burst pipe, the resulting repair may be claimable, and a report that ties the decay to that event is what the claim needs. Rot from a gutter that has leaked for a decade is maintenance in an insurer's eyes, and will be declined.