Article 13 - Is timber treatment always necessary?
You can see woodworm holes but do you need to apply treatment? This article contains useful information to help you decide if treatment is really necessary.
OK you can see some woodworm holes – But is treatment necessary?
Woodworm holes cause alarm
The first sight of ‘woodworm’ holes in a floor, staircase, roof or piece of furniture often causes alarm and understandably most people’s first reaction is to apply some form of treatment. Unless the opinion of an expert has been sought very often this treatment is inadequate. It is usually localised and only applied to the accessible surface of the wood in which the woodworm holes are present – this may not be sufficient.
It is important not to panic. For most wood boring insects found in the UK it takes many years for the intensity of an infestation to build up and cause structural damage. Of course it is possible that upon discovery this point may already have been reached but a few weeks to consider and research what you have found would be time well spent. There are numerous points to consider before any treatment is applied and it is most important that you do not panic or allow yourself to be panicked by others into the application of unnecessary or unjustified treatment.
Woodworm is a generic name for a whole group of beetles that complete part of their life cycle in timber – it is not just one insect. Many of these ‘woodworm’ only infest a specific type of timber or timber at a specific stage in its life e.g. as the standing tree, as logs, green or partially dried timber, decayed timber etc. and some of this previously infested timber may eventually be used in buildings.
Visible evidence of damage caused by this group of insects will remain a permanent feature of the wood however certain of the forest insects die out as the timber is machined and dried so treatment is not necessary. Forest insect damage is sometimes confused with that caused by more serious pests of seasoned timber thus it is very important to identify the wood boring insect responsible for the damage being observed in order to avoid unnecessary treatment. (See ‘Guide to the Identification of Woodworm’ on this site).
Does the sight of woodworm holes mean it is active?
Usually the first time one knows that seasoned wood is actually infested is the sight of ‘woodworm’ holes in the surface of the wood. The holes are formed by an adult ‘woodworm’ emerging from the wood having completed years of its life cycle going through its larval and pupal stage (subject to woodworm type) within the infested wood. The fact that you are now seeing the holes for the first time does not necessarily mean they have just appeared. Of course this is possible but you should consider if you have done something different that has exposed or made the holes visible. They could have been there for years but you have just not noticed or been able to see them before.
If for example the infestation has been identified as one which normally requires treatment such as Common Furniture Beetle (Anobium punctatum) the evidence (holes in the wood) you are seeing could be historic and not be what is termed ‘active’. The infestation may already have already been killed by parasites, the application of previous treatment or died out naturally as the nutrient quality of the wood may have diminished with time. An ‘active’ infestation means live generations (larvae) are still present boring within the wood causing damage and are yet to pupate and emerge through the surface of the wood as adults creating new exit holes.
How do I know if a woodworm infestation is active?
The most common type of woodworm infestation found in our buildings and furniture in the UK is Common Furniture Beetle (Anobium punctatum) hence the word ‘common’ in its name. Assessing whether or not such an infestation is active by visual examination alone is difficult. Generally the sight of fresh clean cut holes in the surface of the timber with ejected frass (bore dust) adjacent to or beneath the holes is a good indication of an active infestation. However it is important to remember that frass will be present in old bore holes within the wood forever and vibration such as that caused by foot traffic sometimes dislodges this giving a false indication of activity. Gouging old Common Furniture Beetle infested wood will always release quantities of frass and cause alarm but this does not necessarily denote that the infestation is active so care is needed. In situations when no obvious evidence is available to confirm whether or not an infestation is active the best course of action is to instigate a monitoring procedure.
How do I monitor if a woodworm infestation is active?
When an adult Common Furniture Beetle emerges through the surface of a piece if timber it is more than capable of chewing its way through newspaper, lino etc. that may be present on top of the wood. Death Watch Beetle (Xestobium rufovillosum) a pest of oak, is known to be able to chew through lead roof coverings, commonly used on churches, and in so doing let water in causing dry rot to occur.
A simple way therefore to monitor whether or not an infestation is active is to stick something like 600 gauge lining paper over the surface or areas of timber where you suspect an active infestation may be present. Ready made wall paper paste or edge repair paste is suitable for this purpose. Such monitoring commonly takes the form of strips of paper along the edges of boards or on the sides of joists. Write on the monitoring paper the date and to prevent others removing it the reason why it is there. Periodic inspections of the monitoring paper strips should take place over the next two or three years, especially during the spring and summer months when adult beetles tend to emerge. If an adult emerges from the underlying timber it will also cause a hole in the monitoring paper meaning the infestation is active. If no holes appear through the paper for three years (for Common Furniture Beetle) the infestation may be considered old.
If the woodworm infestation is in a piece of furniture, gluing pieces of paper for monitoring purposes may not be a practical option. One suggestion is to fill any existing woodworm holes in the furniture with wax polish, preferably one containing a matching stain, thus any new holes will be more obvious.
What else should I consider?
In addition to visual evidence one should also consider the possibility that treatment may have been applied previously. If you are now seeing evidence of an infestation consider the possibility that a previous owner or surveyor may also have seen what you are looking at and treatment therefore may have already been applied. Take into account any documentary evidence such as guarantees, treatment specifications etc. of any previous measures taken to deal with the infestation in the past. Remember woodworm holes will be in the wood until it is destroyed – no treatment will ever remove or seal these holes. It is also possible to analyse a piece of timber for the presence, type and quantity of a previously applied preservative but this is very expensive to do.
If treatment is necessary what should I use?
Never use what is termed a dual purpose preservative when treating woodworm. Dual purpose means it contains a fungicide as well as an insecticide but when treating woodworm a fungicide is unnecessary. Woodworm infested timber built into a property that requires treatment should be dealt with by applying Woodworm Treatment timber preservative not only onto the infested timber surface but also adjacent timbers considered to be at risk. This usually means a whole floor or all roof timbers – not just the visibly infested sections. There are circumstances that will also require the use of gels, creams or pastes which are available to the professional user. (See 'Treatment Guidance' pages on this site for treatment procedures).
Refer to Building Research Establishment (BRE) Digest 307 for further guidance
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