WOODWORM! oh dear, it is a scary name for sure. Fortunately it’s not usually as big a problem as first appears, however, there are exceptions.
In severe cases the damage this tiny insect can cause is quite shocking. This year I’ve already been involved in several pretty extensive repairs, including a complete renewal of a ground floor in a bungalow in Garforth near Leeds; every room in the house had to have all the floorboards and floor joists stripped out and replaced in new timber. That’s one of the floorboards below…
Most of the time though, remedial work involves replacement of the odd floorboard or two and a spray with a suitable HSE approved insecticide.
The thing is, Common Furniture Beetle (its common generic name), is happiest when infesting damp, deadwood, strewn over a forest floor, rather than the dry stuff in houses. Wild wood is wet and subject to fungal and microbial attack, so CFB can thrive within the timber; reducing the wood to hollowed-out trash in short order.
When timber in a building is infested, conditions for the insect are not usually ideal. As a result progress is usually slow, with a higher natural mortality rate, slower growth and less damage from each generation of activity. However, not much moisture is needed to help things along, if there is any excess moisture present, woodworm will thrive.
In houses that means that particular care is needed under poorly ventilated floors, shower rooms, bathrooms and such. It’s not unusual to find a light to moderate infestation in a house and then discover that the sections of floor under the kitchen sink or shower tray are very heavily infested, often with structural damage.
The problem is compounded by the female insects habit of laying eggs in the old flight holes left from the previous generation. Thus the infestation gets going faster in damp areas, then accelerates again with each laying season.
There are some who say that woodworm is not a problem in centrally heated houses; this is not supported by any evidence I’ve seen over the last 30 odd years. I’ve seen it in everything from small back-to-backs and terraces in Armley, Roundhay and Harehills, through to rural cottages and the posh des res in Wetherby, Allwoodley and Harrogate – wood is food for these guys and whilst moisture content plays a big part, it will happily survive and even prosper in relatively dry wood.
Remember that wood is hygroscopic, so it will quickly absorb moisture vapour from air – it does not need to be physically splashed with water to become moist.
What are we looking for?
The holes seen below are typical of CFB. However, in practice it’s surprising how they can be missed. To have the best chance of seeing them use a torch and don’t shine the torch straight at the wood. Hold the torch flat against the surface so the light is shed across the surface, rather than directly at it. This will throw any undulations, bumps and holes into relief and they show up much more easily.
Also, remember that any piece of wood is divided into sections; Heartwood and sapwood. Heartwood is from the middle of the tree and is usually a little darker in colour and denser. This is due to the waste products deposited in the ‘core’ by the tree as it grows (all trees grow by adding new wood under the bark, around the outside – sort of like an onion adding another layer to the existing mass. The Heartwood is less palatable to woodworm (provided it’s not rotting due to fungal attack, in which case it’s fair game).
The sapwood on the other hand is new and fresh at the point the tree is felled. I suppose it’s a bit like meat; most of us prefer spring lamb to tired old mutton. Sapwood is full of the sugars and nutrients the tree was using to grow and the wood is less dense and contains none of the toxins which are in the heartwood – sapwood, particularly moist sapwood is woodworm central.
Let’s go hunting for Common Furniture Beetle.
Underneath the floor is the best place to look for the small holes, but if that’s not very accessible, try looking around the edges, especially under windows (adults usually fly to light and white colours like window sills), around the WC pan, next to the shower tray etc., here is where the holes will eventually appear, even if the first generation emerged elsewhere.
If you have a cellar, then you are at higher risk;. Cellars are where the firewood was stored and that’s where most of the woodworms gets introduced to the home environment. The cellar ceiling may be made of lime plastered timber laths. These are pure sapwood, often ‘riven’ from the edges of raw logs (you can tell this if the laths have undulating edges, rather than flat square ones). If woodworm is in these, it emerges into the void above, which is a cosy environment and they have a good chance of meeting the love of their lives and laying eggs in the void – concentrating the infestation. Joinery in cellars may be unpainted and will have a higher moisture content, so check it all.
In the Roof
Anywhere, but for starters try the ceiling joists and trimmers around the access hatch and the spars next to the chimney (where it may be moist and where light may leak in). Any light when you turn your torch off? Have a look there. Look out for any spars with ‘wany edges’, where the bark has been. This indicates very high sapwood content. If you find something here though, check it’s not just Bark Borer Beetle, which is the civilised cousin of woodworm and quite harmless.
Anywhere of course, but look at the edges of the treads in particular; the treads and rises are often ‘flat sawn’ so the curved (bullnose), edge of the treads may have a high sapwood content, which is ideal for woodworm to thrive in. Do look at the stair strings and joinery too though.
In other products.
Not only solid timber is attacked – woodworm is very partial to old plywood. In the past plywood was glued with casein, which is basically stewed animals. The sandwich, of this goo and cheap timber, which is unsuitable for conversion to anything else (high sapwood content again), is perfect woodworm fodder. Electricity and gas meter boards, panelling under stairs and in old pantries and such are all places to check. When I first trained as a timber infestation surveyor, back in the early eighties I was privileged to visit The Princess Risborough laboratories, where many of the treatments and research in woodwork control were developed. The scientists used rack after rack of casein glued plywood to breed woodworm for testing treatments on.
So you’ve found holes and think it maybe woodworm? Ideally call in a specialist surveyor who at least has CSRT or CTIS certification. Most companies who are members of the Property Care Association will have this minimum qualification. Don’t entertain anyone who spends time and money advertising themselves as a specialist, if he hasn’t the time or money or sufficient respect for you, to bother getting qualified.
Is the woodworm active? This is where some skill comes in. CFB has a breeding season just like many creatures. This is the ‘flight season’ when mature larvae pupate below the surface of the wood and emerge as beetles to mate and lay eggs. Summer is the season of love, but the period is a bit flexible in houses, due to heating and such, so you may get fresh holes anytime between about May, through to September. New holes are usually part filled with ‘frass’ which is the poo of woodworm. A trained specialist can identify the species of the infestation just from the texture, size and colour of the pellets. The size and shape of the ‘flight holes’ is also crucial of course.
There are some who say that active woodworm can only be proved if “living larvae are found’. This is literally correct, but in practice living larvae are difficult to get at; being happy deep in the wood. It takes ages to carefully dissect wood to find them and afterwards the wood is destroyed, whether you are successful or not (plywood is an exception, just peel away the layers and hey presto; exposed juicy larvae just fall out). An experienced specialist will access the situation and make a judgment based on a number of factors:
Any adult carcasses
Fresh ejected frass
Number and density of the flight holes and ‘the look’ of them
Risk assessment of the chance of leaving the infestation as opposed to treating it.
He should then be able to provide a recommendation based on sensible methodology – it is not good practice to just recommend treatment whenever flight holes are found. If a surveyor recommends treatment or diagnoses woodworm and does not recommend treatment, ask why – he should have a reason for any recommendation.
Beware unqualified ‘specialislist’ recommending widespread treatment for “woodworm”. Make sure that the surveyor identifies the species infesting the timber including the latin name so there’s no confusion – see this previous post to see how much can be saved if you take care and avoid being conned – what is woodworm?
I’ve treated many hundreds of infestations over the last three decades. I don’t have two heads and as far as I know, nether do my sperm. There’s been lots of publicity; shouting about how dangerous the chemicals used for woodworm treatment are. Publicity is often another word for rubbish – just read the Daily Mail or The Daily Star for example.
The facts are that there is no link between any of the modern Health & Safety executive approved treatments and ill health. I wouldn’t drink the stuff we use, just as I wouldn’t drink bleach or after shave (I’ve drunk most other things though). It must be used only when needed and must be applied by trained and certified technicians, under the guidance of a qualified surveyor. If that is done there is no risk to you. Technicians, using the stuff every day are at risk of course, so that is why they are togged up like astronauts.
Cats and goldfish are exceptions – cats have died as a result of permethrin toxicosis when tolerant dog flea powder has been mistakenly applied to them. Permethrin is very dangerous to aquatic life. This needs to be taken into consideration when it is used and especially when waste product is disposed of. It is safe once it is dried into the wood; cats are at risk during treatment and for a short time after though (this is less to do with permethrin than cats – they also drop dead because they love drinking anti-freeze….. I have two cats and they are both weirdo’s).
Modern treatments include a variety of chemicals, though for most infestations I recommend a Permethrin based insecticide. Permethrin is a synthetic pyrethroid with very low mammalian toxicity (cats excepted), It kills woodworm stone cold though. It is a contact insecticide so it will protect wood from re-infestation and will kill adults emerging from below during the flight season. A thorough spray to ‘run off’ is all that’s required.
Boron products work well too, though these need to be ingested so are less effective on severe infestations; they have a dual action though, inhibiting fungal growth too. It’s a question of balance and a decent timber infestation surveyor will make a judgement on the most appropriate product.
I’ve gone on a bit, but do please ask if there’s anything else you’d like to know. I survey anywhere in the Yorkshire area, so you can always give me a call at Brick-Tie preservation if you need specific advice or a survey. Outside Yorkshire, try the Property Care Association Web site, which has a nice ‘find a contractor’ and ‘find a consultant’ section; just type in the area and you’ll get a list of my fellow members.