Ensure that your woodworm problem has been clearly diagnosed before agreeing to chemical treatment and remedial work. Unfortunately timber treatment contractors are not legally required to complete any training or certification.
In 2002, a 39 year old man died during a routine fumigation to treat woodworm in the roof of a church in southern Germany. The chemical used was sulfuryl fluoride, a highly toxic gas that has no odour or colour. There's no need for alarm, but pesticides are potentially dangerous and you should ensure that the contractor:
- Informs you which chemical treatment will be used and how it will be applied. As mentioned above, some can be environmentally unsound. Avoid lindane, pentachlorophenol (PCP), tributyltin oxide (TBTO) altogether - acute exposure to these chemicals can cause ongoing medical problems.
- Informs you of any appropriate training.
- Is a member of the Property Care Association, part of the British Wood Preservation and Damp Proofing Association. You can find a PCA contractor member at www.property-care.org.
- Uses PPE (personal protective equipment).
- Gives you a guarantee for the work.
What costs are involved?
For an average house, you're looking at £500-£1,000 for blanket pesticide treatment.
An application of borax solution is relatively cheap – around £28 per 25 square metres for surface treatment of a light to medium woodworm infestation. Boron-based paste or gel is slightly more expensive, while leave-in rods that remain in timber suffering from permanent or seasonal dampness cost around £16 for 10.
Permethrin-based treatments are cheaper – 1 litre of the popular Microemulsion Woodworm Killer Concentrate costs £7 and makes 25 litres, sufficient to treat 100 square metres of timber.
Repairing woodworm damage
After woodworm has been eradicated, structural woodwork should be replaced with pre-treated timber. Non-structural timber, including furniture, can be tarted up once the treatment is complete. Some people find that a peppering of flight holes gives woodwork character!
If you don't, try filling holes with a mixture of beeswax and turpentine or a commercial wood filler. Many beeswax furniture polishes provide protection from future larval infestation. For painted wood, fill the holes then sand the surface down and redecorate.