When to Specify Woodworm Treatment

Was woodworm treatment necessary?

timber decay

A screwdriver is useful for assessing timber decay but appears to be the diagnostic tool of choice for this particular damp proofing company.

I was recently asked to review a report, supplied by a large National damp proofing company, on behalf of a client, who spent thousands of pounds on unnecessary treatment, including timber preservatives. I say ‘unnecessary’ but perhaps it would be more correct to say that the woodworm treatment wasn’t proven as being necessary.

Perhaps it might be first useful to explain what woodworm are…

Woodworm

Woodworm is a collective term, which is used to describe all classifications of wood-boring insects.

Wood-boring insects use wood as a source of food, and in the UK at least, mainly consist of beetles.

Furniture Beetle, Woodworm

Furniture Beetle (Anobium Punctatum)
(Source: https://www.naturespot.org.uk/species/common-furniture-beetle)

The most common type of wood boring insect in the UK is the ‘Furniture Beetle’, or ‘Anobium Punctatum’ to give its latin name. It is brown, usually about 3-4 mm in length and has a prothorax that resembles a monk’s cowl.  Whilst less common in the UK, timber can also be infested by the much larger Death Watch beetle (Xestobium Rufovillosum) (which is considerably larger at 7- 8mm long), the House Longhorn and the Powder Post beetles. In all species there is a grub like larvae stage, lasting several years, whereby the larvae bores around under the surface of the wood. This is where the most damage occurs.

Note insect flight exit holes in timber

Note insect flight exit holes in timber

A furniture beetle’s Life cycle

The infestation process starts when the female beetle lays its eggs directly into the timber through cracks, crevices or even existing flight holes. The eggs are oval in shape and laid in batches of between 20-60. After about 5 weeks, the eggs hatch and the larvae (woodworm) tunnel down into the wood and spend the next 1- 5 years digging their way around munching through the timber until the next stage in its life cycle. It is in this stage that the greatest structural damage to the wood takes place, and this damage goes unseen due to its location within the timber. The larvae then carve out a ‘pupal’ chamber near the surface of the wood in which the larvae ‘pupates’ into a beetle over a 6-week period. The fully formed beetle then burrows its way to the surface and out, leaving a circular ‘flight hole’ about 1-2mm (roughly the size a dart would make in a dart board). This is the final stage of the beetle’s life cycle, with the females living for around 14 days, and the males only 4 days.

Wood boring beetles thrive in damp conditions; indeed many living trees can have beetle infestation. Species such as the furniture beetle prefer the softer ‘sap’ wood from which they feed off the cellulose, whereas the larger Death Watch beetle is especially fond of hard woods such as oak and beech. It is worth pointing out that the ‘heart wood’ of say, a piece of oak, is usually left untouched by beetles and just the outer sap wood is subject to beetle attack.

Signs of beetle attack

Again, the screwdriver is used in support of woodworm treatment with insecticide.

Again, the screwdriver is used in support of woodworm treatment with insecticide.

Apart from the obvious flight holes left by the beetles, a powdery dust called ‘frass’ can often be seen on floorboards and other wooden surfaces. Frass is the excreted wood that the larvae produce.

In old historic timber framed buildings, especially thatched cottages, there may be signs of beetle attack, evidenced by frass on the face of the timbers, in a honeycomb pattern. If the wood has clearly suffered beetle attack, there is a need to determine whether the timber still has structural integrity. The frass must be scraped off and the heart wood of the timber examined. It is very rare for a beetle attack to penetrate deeply into the heartwood of a piece of oak, so its structural integrity usually remains.

Old bore holes or new?

To establish whether beetles are still present in timber, where there is evidence of frassing, is quite straightforward. Once the frass has been scraped off, a piece of tissue paper can be stuck over several suspected areas of wood and sealed round all edges with a water soluble glue, and left from April to August (this is the flight stage in the lifecycle). On inspection, there may be larvae and beetles trapped or flight holes puncturing the tissue paper. All of these point to an active infestation. Also, checking spider webs in old timber framed buildings to see what’s entrapped can help to establish the types of insects that are present. You should also recognise, that many timbers were installed with insect flight exit holes, because wood boring insects also attack trees as well as cut timber. The majority of flight holes observed on timber from historic buildings are often at least 100 years old. This is because the infestation took place within the living tree before it was even felled, due to the moist conditions present in nature. Needless to say, whether the bore holes are old or new, forms a critical deciding factor in whether or not woodworm treatment is required.

Case Study

In august 2017, the property in question was subjected to a damp and timber survey, by a large national damp proofing company. The client knew they’d be expensive but wanted the assurance of dealing with a ‘brand’ name.

Damp & Timber treatments specified costing over £22,000

Damp & Timber treatments specified costing over £22,000

In total, this company specified over £22,000.00 worth of work, which included over £3000.00 for treatment of wood boring insects and timber decay. Post completion of the work, another surveyor attended the property and informed my clients that he was of the opinion that this work wasn’t necessary, and that my clients had been mis-sold these treatments. Obviously alarmed, they asked me to carry out a review of this companies survey report and survey methodology.

The Survey

There were many issues, both with their investigation for rising damp, and their assessment of timber decay, but for the purposes of this blog, we’ll remain focussed on their assessment of wood boring insects and the treatment specified.

The surveyor repeatedly made claims in his  report that there were, “current attacks by wood boring insects,” and of course used the word ‘current’ to justify his specification for timber preservative treatment.

In fact, no evidence whatsoever was presented proving a current attack, failing to even take or record timber moisture contents; a significant omission. BRE Good Repair guide 13, highlights the following as indicators of live infestation:

Indicators of insect activity are:

  • Freshly cut exit holes and recently ejected bore dust (frass), although dust may have been shaken from timbers by foot traffic.
  • Insect larvae extracted by probing the tunneled timber. In practice the larvae are difficult to find.Identification of the insect causing the damage is important, not only in deciding if any wood preservative treatment is necessary, but also in deciding if any other action is required.

From the flowchart below, it could be seen that the company concerned failed to demonstrate or prove that insect infestation was active, and therefore failed to reasonably comply with this guidance. If no live infestation was present, then the next step is to assess whether timbers contain more than 20% sapwood; if the answer is no, then no treatment is required.

BRE Good repair guide 13

Flowchart taken from BRE Good Repair Guide 13.

Further guidance is given in BRE Digest 307, which states that; ‘The presence of damage by wood boring insects does not always indicate a need for remedial treatment.’  The common types of damage found in building timbers have been divided into three categories:

BRE Digest 307

Taken from BRE Digest 307

Again, the table above highlights the importance of identifying the species before deciding on treatment measures, and throughout the report, wood boring insects were only discussed in general terms, with no identification being made. What we know unequivocally, that no proof. whatsoever was provided to demonstrate this timber treatment was necessary.

As discussed earlier, the client was charged over £3000.00 for timber preservative treatments, the insecticide, being a Permethrin based product. If you want to understand the mark up on these products, 5 litres of Permethrin based product, can be obtained from a brand name company, for around £9.00; enough to cover around 15-20 square meters of timber.

How we deal with woodworm organically

It is vitally important to get to the root cause of the woodworm issue so that a long-term solution can be implemented. Since the woodworm larvae thrive in damp timber, it makes sense to identify and remedy the cause of that damp, and by doing so the infestation will cease, and more importantly, not come back.

Generally speaking. woodworm like their meals with a little ‘gravy’ so you should focus on the root cause of the damp in timber and we would generally look to treat this issue in the following simple manner…

  1. Eliminate the source of moisture and introduce rapid drying
  2. Assess the severity and depth of timber infestation and damage
  3. Replace any structurally unsound timber
  4. If required improve ventilation to the affected area

It is a treatment plan almost identical to what we’d specify to deal with an outbreak of fungal decay such as dry rot.

It is a sad fact that the damp proofing industry has enjoyed great success by unnecessarily recommending that damp timber infested by woodworm is covered with litres of toxic chemicals. The main issue with this method is that it does not address the primary reason as to why the timber is infested in the first place, Since the timber is still damp after being treated with chemicals, there is a likelihood of re-infestation occurring.

Furthermore, these toxic chemicals can cause environmental damage and might even require a licence if being used in close proximity to any protected species. Thankfully though, the inadequacy of this practice is now becoming better understood and is well documented in BS7913: 2013 “Guide to the conservation of historic buildings”. It also identifies that chemical treatment does not actually penetrate deep into the timber, but only just under the surface and therefore any larvae, which are active inside, won’t necessarily be affected.

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Plaster Beetles

 A less well publicised visitor
Source:www.bcpa.org.uk

Source:www.bcpa.org.uk

We’re all heard of woodworm, the term used for the larvae of the destructive furniture beetle, precisely for the reason that they can be destructive but there are other forms of infestations not generally considered harmful that you may not be aware of, the plaster beetle is one such visitor. Of course, if you’ve suffered from a plaster beetle infestation then you’ll be well aware of this pest. We recently took a call from a client asking for advice on a plaster beetle infestation in a new build property. The constructor had called in a pest control company who had fumigated but the client experienced re-infestation within two weeks of the treatment.

Plaster beetles get their name from the fact that they are often seen in new properties where damp plasterwork often provides ideal environmental conditions for these visitors. Also known as scavenger beetles, plaster beetles are part of  the lathridiidae family, a family with over 1050 described species.  This particular visitor is an unpleasant nuisance rather than being harmful but nevertheless, no one would want a plaster beetle infestation in their home. The problem is not often reported on because they are relatively innocuous however we found this report relating to a new build infestation that gives a feel for how unpleasant a plaster beetle infestation can be…

“In September, the couple spotted tiny insects in the kitchen. “I went into the bathroom and saw plaster beetles all over the wall,” says Jane. “As fast as I cleaned them away, they kept on coming. They were all over the bedroom and in the kitchen. The microwave, toaster and a television were so badly infested that I had to throw them away.”
The couple were told by the council’s environmental health department to open the windows and turn up the heating, which made things worse.
“Barratt said it had never heard of this method and recommended we used fly spray. I was using 10 cans a day – and still they kept coming. We discovered orange mould under a picture frame and thick green mould under the sink,” says Jane.
At the beginning of November, they consulted an independent environmental adviser, who said that they should have just left the trickle vents open and turned the heating down to 14-16C all day. This seemed to have an effect, but they also had to buy two dehumidifers. “I can’t afford to go on paying for the dehumidifiers to be on 24 hours a day,” says Jane. “We are so upset, as this was our dream house and we just want to enjoy it.” The couple are hoping the infestation might finally be over. “But we can’t be sure, if the conditions change, they might be back.”

What we noted from this newspaper report is how badly the homeowners were advised and how wide the difference of opinion as to how these pests should be dealt with.

Identification

A range of plaster beetles. Source: bugguide.net

Since plaster beetles thrive in damp conditions then they are more prevalent during the wetter seasons but essentially, if you have damp conditions that lead to mould colonisation then there is a small risk of plaster beetle infestation. They have been a particular problem in some new homes where properties have been handed back to new owners without being properly dried out; particularly where properties have been flooded due to careless plumbers; an issue we have seen many many times in new build. Residual  construction moisture can be a temporary issue in new build properties but in the main, properties should be relatively dry unless there is or has been some additional underlying issue. Indeed, it may be that the building fabric is relatively dry but you are suffering from high levels of relative humidity that support fungal growth. Interstitial condensation can be a particular problem since mould formation can occur in hidden voids, thereby providing a hidden food source for beetle colonisation.

Plaster beetles can be anything from 0.8mm to 3mm in length and have a life cycle of 13 to 28 days. Adult beetles deposit their eggs near a food source (mould) and when larvae emerge they feed on the mould spores before eventually pupating into adults. Pupation can take up to five months dependent on the availability of food. Some types of plaster beetle are reasonably good fliers and can be attracted to light, which is why you may see them congregated around a light source or near windows.

Treatment 

Generally speaking we are not great believers in chemical treatments and prefer to deal with infestations like this in a more natural way that avoids spraying harmful chemicals in the home. Since plaster beetles feed on mould and mould is caused by damp conditions in the home then doesn’t it simply make sense to deal with the issue at source by removing the source of moisture and the source of food? Chemical treatments can never deal with the underlying cause of the problem, which is dampness and subsequent mould colonisation. Moreover we simply do not like the idea of spraying harmful chemicals in the home and the chemical effects will reduce over time, thereby requiring re-treatment since the underlying cause has not been addressed. There is also an option of heat treatment, whereby the property is heated to 45 degrees C. This temperature should kill off any plaster beetle colonies in the home but again our main concern is that this does not address the underlying cause so there may well be a risk of re-infestation.

You will need to address the underlying cause and in simple terms you should consider 5 factors:

  1. Identify and eliminate the source of moisture
  2. Promote rapid drying
  3. Eliminate the food source (If possible)
  4. Ongoing management of high relative humidity in the home.
  5. Regular cleaning protocol to aid beetle management

The source of moisture may be a plumbing leak, penetrating damp or condensation damp and if you are in a new build property, you may simply have to deal with temporary construction moisture by promoting rapid drying. You may want to consider hiring snail fans to dry out walls and a dehumidifier to mop up the excess humidity. If this is not successful then it is likely that you have a more significant underlying source of moisture that needs identifying.

If mould colonisation is obvious then treat this with a proprietary fungicidal spray to help eliminate the food source and where plaster beetles are seen then they should be vacuumed as frequently as possible to help manage the population whilst the underlying cause of dampness is being addressed.

The underlying cause won’t always be obvious, in which case you may need to call in a Chartered Building professional. If you call in a pest control or damp proofing company then you should expect to be sold chemicals or heat treatments, money that would be better directed towards correct diagnosis of the underlying cause of moisture.

Flour Beetles
Screen Shot 2015-12-22 at 10.39.00

Flour Beetle (Tribolium Castaneum). Source Wikipedia

As an aside to this blog, we were recently asked to advise on a flour beetle infestation in a kitchen. The client complained of frequently seeing larvae on the kitchen worktops but had no idea what they were or where they were coming from. Similar to  plaster beetles, they are another relatively innocuous, but nonetheless unpleasant visitor that can invade kitchen foodstuffs, particularly flour and cereal products. However, the issue of seeing larvae only on kitchen worktops gave us a strong hint as to the source of the problem… “Do you have a toaster on the kitchen worktop,” we asked? “yes, we have a double toaster” came the reply. We advised the client to open up the toaster and clean out all the old breadcrumbs that had accumulated in the base and sure enough it was packed with two years worth of breadcrumbs and a flour beetle infestation that was completely eradicated once the toaster was cleaned out and the food source was eliminated. Some of these toasters have cleaning trays in the base that can be removed for cleaning but they are simply not up to the job. Of course we’d completely understand that many would prefer to simply throw the toaster away rather than clean it out but we’re not advocating mass toaster disposal without first checking that this is the source of the problem.

 

 

 

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