Woodworm advice needed

[Hindsight]

We own an old place that has seen better times. After fifteen years of blood, sweat, and tears it's passable as a home. Obviously being an old place it's had woodworm. While fixing it up I found plenty of evidence of common furniture beetle and death watch but they all seemed to be prior infestations and I repaired where needed.

The other day, while moving the furniture in the living room, I found a floorboard that is basically just a pile of dust. It definitely wasn't like that a few years ago so we have an active problem. Closer examination leads me to believe that the boards either side are probably infested too and possibly a few other boards - it's hard to tell as the frass doesn't hang around for long on the floor. I've inspected joist in the living room in the past and they showed no signs of issues, I don't know what timber it is but it's hard as hell and so probably fairly woodworm resistant.

My understanding is that if we keep the moisture content low enough (sub 12% iirc) it'll kill off the woodworm. The area that's affected doesn't get much heating so I could imagine the moisture content would be a bit high which is probably the underlying issue.

My question is what is the best course of action? The house is constantly trying to break and / or fall down so I keep a careful eye on it and I see no obvious evidence anywhere else of an infestation. I'm tempted to rip up the affected boards and replace them and then make sure that end of the room gets a good bit of warmth from now on. I'll obviously inspect the joists again while I'm in there. I'm hesitant to use any chemical treatment although a coating of permethrin might be necessary here. Any advice gratefully received.

 

[aockenden]

Does natural balsam turpentine kill woodworm?

 

[Hindsight]

My understanding is that it will work but in all honesty permethrin is probably a safer treatment, assuming I go with any treatment. It's not advisable to breathe in solvent vapours and I don't want to burn the house down.

 

[Toby Newell]

Matt Green is the man to wait for, he did his thesis on wood boring insects. In the mean time you have me. I only work with the buggers, but have done so for decades.

Are you in the UK? You sound American. Please post photos.

A few points whilst we are waiting for Mr Green...

1. Beetle will eat hardwood just as well as softwood if conditions are right. CFB prefer softwood, DWB prefer hardwood, PPB munch both, in my experience. In general they prefer sapwood only but if damp is severe and pervasive they will move onto the heartwood as it is broken down by microbes and is easier to munch.
2. I have never seen frass on the surface, it would be underneath the boards.
3. Yes, high moisture content is the biggest factor. 12% is still quite high 6% to 10% is common in modern homes. Matt has posted research that they can grow as low as 4%. You want to try and get down to 8-9% if you can.
4. How large is your room! Heat part of it??? You need to heat and ventilate your entire house! Relative humidity in the air as a whole largley determines wood moisture content even if you have rising or wicked damp from joist. The rules are, heat, ventilate and ameliorate sources of water ingress ie rising or wicked damp from compromised joist either via subsoil, pier stack or wicked from wall.
5. If you have a live colony then remove compromised boards, if a board is dust then often local joist are affected too you may need to cut in some new joist / fit strenthening noggins. Permethin kills by contact, you need to really soak the areas affected, including joist, from underneath.
6. Worm mature and fly in the spring, they shouldn't be leaving now. They might leave every other year or three.
7. Coating now avoids potential damage to bees and other pollinators but Permethrin is very toxic to cats so be aware. Coating the top surface is of limited use if you are going to sand it. In isolated areas or furniture you can use a hyperdermic needle, this injects the killer into the galleries which is more effective.

Logical deductions:

Worm love damp. Ergo, you have damp.
Worm will propogate but preferentially attack the dampest areas.
If you have severe worm in an isolated area, it indicates you have severe damp in the same area. Heating and ventilating the entire area is beneficial but you might want to look for a localised source of damp. This is often from walls / piers where damp masonry meets timber. When fitting new joist, isolate it by coating it in a waterproof medium where it contacts any masonry.

 

[Toby Newell]

Matt could advise you on the effectiveness of turpentine. Seeing as it is distilled from pine resin then is is feasible it will quickly evaporate but leave trace heavier odour chemicals, some of which may act like pheremones to beetle! ie it might just scream 'dinner here!'

Real gum turpentine smells amazing but is pretty silly to go sloshing around your house, it is literally used as stove and car fuel. Meths would work better and evaporate faster and be slighly less of a fire hazard. I suspect xylene would work best but that is even more flammable.

I guess soaking a small item in turps might work, but then popping small items into the freezer is an even better method. If you use turps, don't burn your house down. Although technically that would also reduce your woodworm problem by around 100%.

 

[Lacan07]

If its localised at this point I'd probably replace whilst spraying the adjacent boards.

 

[Lacan07]

I don't know if true but do they say the most common cause of woodworm is when someone introduces an infected piece of furniture into the house? Matt will know I'm sure.

 

[Toby Newell]

I don't know if true but do they say the most common cause of woodworm is when someone introduces an infected piece of furniture into the house? Matt will know I'm sure.

That's a bit of a myth Paul. It might hold true in a block of flats in the middle of London, but in a country cottage you have wood boring beetle all around you! I attribute approximately 1% of the infestations I find to introduced furniture. Incredibly rare.

It is possible, probable even, that hundreds of years ago, non kiln dried or pressure treated timber used in construction would have an almost 100% chance of containing some woodworm as green oak was often left to dry outside in a 'shed' with open sides for a year or two (and up to 20 years) many times in a forest, surrounded by woodworm.

Woodworm are more common (in floors) next to the outside, ie ground floor garden room, adjacent to the garden, often following a track along the joist.

 

[Hindsight]

Wow, thanks for all the help. As requested here are some pictures and a bit more information. I'm in the UK, near Worcester.

Overview shot, the wall to the left is internal the wall facing is external.

I opened up part of the rotten area so you could see the level of damage. I've not lifted the board yet, that's tomorrows job.

The holes are about 1mm so I'm thinking CFB. The boards are also some sort of pine.

Another area of damage on the next board over. This was already damaged so I can't tell if this is all new.

Context for the size of area we're talking about.

Meter reading from the middle of the damaged board.

From near the worst damage. I tested a load of spots around the room and generally got low 12%.

So, the moisture levels are too high in this area but I'm pretty certain it's not damp coming in from outside. This is the living room and we don't tend to use it much so the heating is turned off, it's also naturally a cold room (lovely in summer, though). The only time it gets heated is a few days over winter when we have the stove going. This area with woodworm is under a chair and treadmill normally, so air flow is limited. I'd bet even when we do get the room warm this area stays cold.

One part of puzzle I'm pretty sure I know the answer to is where they came from. We've almost certianly left firewood in the living room at some point. From now on it's staying outside until the minute before it gets burnt.

I'm on top of keeping the place ventilated and heated usually. This room just gets forgotten, we live in the kitchen. Tomorrow I'll go around and take moisture readings from all the floors, I'd put money on all the rest being fine.

 

[Lacan07]

That's a bit of a myth Paul. It might hold true in a block of flats in the middle of London, but in a country cottage you have wood boring beetle all around you! I attribute approximately 1% of the infestations I find to introduced furniture. Incredibly rare.

It is possible, probable even, that hundreds of years ago, non kiln dried or pressure treated timber used in construction would have an almost 100% chance of containing some woodworm as green oak was often left to dry outside in a 'shed' with open sides for a year or two (and up to 20 years) many times in a forest, surrounded by woodworm.

Woodworm are more common (in floors) next to the outside, ie ground floor garden room, adjacent to the garden, often following a track along the joist.

Ah, that interesting. I don't know where I picked that up from, someone I met a few years back.

 

[Toby Newell]

Ah, that interesting. I don't know where I picked that up from, someone I met a few years back.

Lol, I think the amount of erroneous 'received wisdom' outweighs accurate information by several orders of magnitude. Funnily enough, as I do both antique restoration and floors I would say the incidence of worm is 100:1 floors to furniture. Often on the feet! Implying beetle migrated from a damp floor! Most antiques have horrible (to a worm) hardwood veneers and rabbit skin glue, you often find them in drawers, at the back edges or on feet.

 

[Toby Newell]

Wow, thanks for all the help. As requested here are some pictures and a bit more information. I'm in the UK, near Worcester.
View attachment 12218
Overview shot, the wall to the left is internal the wall facing is external.
View attachment 12219
I opened up part of the rotten area so you could see the level of damage. I've not lifted the board yet, that's tomorrows job.
View attachment 12220
The holes are about 1mm so I'm thinking CFB. The boards are also some sort of pine.
View attachment 12221
Another area of damage on the next board over. This was already damaged so I can't tell if this is all new.
View attachment 12222
Context for the size of area we're talking about.
View attachment 12223
Meter reading from the middle of the damaged board.
View attachment 12224
From near the worst damage. I tested a load of spots around the room and generally got low 12%.

So, the moisture levels are too high in this area but I'm pretty certain it's not damp coming in from outside. This is the living room and we don't tend to use it much so the heating is turned off, it's also naturally a cold room (lovely in summer, though). The only time it gets heated is a few days over winter when we have the stove going. This area with woodworm is under a chair and treadmill normally, so air flow is limited. I'd bet even when we do get the room warm this area stays cold.

One part of puzzle I'm pretty sure I know the answer to is where they came from. We've almost certianly left firewood in the living room at some point. From now on it's staying outside until the minute before it gets burnt.

I'm on top of keeping the place ventilated and heated usually. This room just gets forgotten, we live in the kitchen. Tomorrow I'll go around and take moisture readings from all the floors, I'd put money on all the rest being fine.

Great photos thank you and lovely wide boards. Yes 15 and 16% is way too high.

You have already answered your own questions. Either you heat the room year round, or expect woodworm.

Firewood is an incredibly common source but don't beat yourself up about it, beetles can fly and your house has a million cracks and opportunities for adventurous ones to alight on your floor.

I see rampant woodworm in hundreds of Victorian terraces and semis, miles away from woodland or firewood.

If your wood is 15% moisture you are probably going to get worm sooner or later.

 

[Toby Newell]

I don't know if true but do they say the most common cause of woodworm is when someone introduces an infected piece of furniture into the house? Matt will know I'm sure.

The OP makes a fantastic point. Apart from worm dormant in green timber the biggest source of worm surely must be firewood. In fact, I guess it is possible at lot of the extinct worm damage I see in town was originally introduced via infested firewood as open fires were very common even in towns up to the 1960's

 

[Matt Green]

I need some sort of Bat Signal like a silhouette of a wood-boring beetle shone on low cloud.

if we keep the moisture content low enough (sub 12% iirc) it'll kill off the woodworm

Yes, eventually, but it is a lifecycle breaker so you will have 2-5 years of adults emerging and flying away. Don't panic, it's a good thing.

My question is what is the best course of action?

Do nothing, watch and wait patiently without panicking. Very few people sell this as a product, but a considered approach is better for the house and cheaper for you.

Does natural balsam turpentine kill woodworm

Terpene hydrocarbons (α-pinene, β-pinene, limonene, 3-carene, and camphene)? sure, probably fairly well. the trick is getting it to the insects as with all pest control. It should penetrate timber adequately but it is not registered as an insecticide and therefore you would be using it off-label. I can neither condone nor recommend you do this (obviously, given what I do for a living).

My understanding is that it will work but in all honesty permethrin is probably a safer treatment, assuming I go with any treatment. It's not advisable to breathe in solvent vapours and I don't want to burn the house down.

Yes, probably but let's not get silly- we don't know if there are any insects there yet and what risk they pose to the timber, if any, that warrants throwing insecticide around.

Toby's advice is good, no notes on that other than the risks of using off-label insecticides.

I don't know if true but do they say the most common cause of woodworm is when someone introduces an infected piece of furniture into the house? Matt will know I'm sure.

Yes, it that piece of furniture and usually it's because the furniture has been stored in a cold damp location, brought inside, dried out and now the adult beetles are emerging to lay their eggs elsewhere in timber with a higher moisture content (so no treatment required, carry of with your life with a new upright piano/sideboard/bookcase/other piece of furniture with a cheap plywood animal glue back that was up against an external wall). The risk is in providing a source of timber (damp or with a density low enough to sustain a wood-boring beetle infestation- see Zebra's previous posts on the matter). If there is no suitable timber the adult beetles will fly away in April-June.

Roofing leaks and high ground levels are likely to biggest cause of wood-boring beetle infestation in structural timbers. The former for Furniture Beetle and Deathwatch, the latter for wood-boring weevils.

Thank you for the pictures Hindsight- good work. Old furniture beetle damage in pine floorboards. Very much Toby's wheelhouse.

14.7%. Have you calibrated that Resistance Meter for Pine? (it will a setting in the instructions at the back of the manual)

One part of puzzle I'm pretty sure I know the answer to is where they came from. We've almost certianly left firewood in the living room at some point. From now on it's staying outside until the minute before it gets burnt.

The damage is probably older than: me keep your firewood where it's convenient. I've never been convinced about firewood as a reliable source of infestation. Wood-boring beetles can find one section of joist plate that has decayed in an otherwise untouched row of cottages in a city. They have an incredible sense of smell- if you have timber they can lay eggs in- they will find it. They are not going to wait to be carried in on a basket of firewood, it's not a great evolutionary strategy for survival.

This is probably the best advice in the thread so far, from Toby:

5. If you have a live colony then remove compromised boards, if a board is dust then often local joist are affected too you may need to cut in some new joist / fit strenthening noggins.

Cheers,

Matt

 

[Toby Newell]

I need some sort of Bat Signal like a silhouette of a wood-boring beetle shone on low cloud.



Yes, eventually, but it is a lifecycle breaker so you will have 2-5 years of adults emerging and flying away. Don't panic, it's a good thing.



Do nothing, watch and wait patiently without panicking. Very few people sell this as a product, but a considered approach is better for the house and cheaper for you.



Terpene hydrocarbons (α-pinene, β-pinene, limonene, 3-carene, and camphene)? sure, probably fairly well. the trick is getting it to the insects as with all pest control. It should penetrate timber adequately but it is not registered as an insecticide and therefore you would be using it off-label. I can neither condone nor recommend you do this (obviously, given what I do for a living).



Yes, probably but let's not get silly- we don't know if there are any insects there yet and what risk they pose to the timber, if any, that warrants throwing insecticide around.

Toby's advice is good, no notes on that other than the risks of using off-label insecticides.



Yes, it that piece of furniture and usually it's because the furniture has been stored in a cold damp location, brought inside, dried out and now the adult beetles are emerging to lay their eggs elsewhere in timber with a higher moisture content (so no treatment required, carry of with your life with a new upright piano/sideboard/bookcase/other piece of furniture with a cheap plywood animal glue back that was up against an external wall). The risk is in providing a source of timber (damp or with a density low enough to sustain a wood-boring beetle infestation- see Zebra's previous posts on the matter). If there is no suitable timber the adult beetles will fly away in April-June.

Roofing leaks and high ground levels are likely to biggest cause of wood-boring beetle infestation in structural timbers. The former for Furniture Beetle and Deathwatch, the latter for wood-boring weevils.

Thank you for the pictures Hindsight- good work. Old furniture beetle damage in pine floorboards. Very much Toby's wheelhouse.

14.7%. Have you calibrated that Resistance Meter for Pine? (it will a setting in the instructions at the back of the manual)



The damage is probably older than: me keep your firewood where it's convenient. I've never been convinced about firewood as a reliable source of infestation. Wood-boring beetles can find one section of joist plate that has decayed in an otherwise untouched row of cottages in a city. They have an incredible sense of smell- if you have timber they can lay eggs in- they will find it. They are not going to wait to be carried in on a basket of firewood, it's not a great evolutionary strategy for survival.

This is probably the best advice in the thread so far, from Toby:



Cheers,

Matt

Just call me Robin... interesting to hear it IS probably furniture rather than firewood, or as Matt and I both summised, random insects coming in from outside.

I have visited over 1,000 period properties with pine floor boards all over the country, most of them in London, pretty much all of them had woodworm somewhere, even if it was one board. Seems to me the beetles have quite an impressive range.

 

[Hindsight]

So I've lifted three boards to asses the extent of the damage and I'm quietly confident that it's not as bad as I first suspected. The board that tipped me off to a problem was completely eaten away, I pulled it away with my hands.

Board number two (the one nearer the camera in photo above) was in rough shape, it fell apart badly enough while lifting it that I won't be able to salvage it. The third board (nearer the camera again) came up but split in the process. You can see the pieces it in the shot above (resting on the treadmill), I've repaired boards like this before. That left me with the hole shown below. I've cleaned and de-nailed (salvaged most of the nails). You can just see a beam running parallel to the floorboards at the bottom of the opening.

The joists, as far as I can see haven't been attacked. I'll do another thorough inspection but I'll be treating everything I can reach.


Unfortunately, the "sleeper joist" (there's no sleeper wall, just a couple of very rough and ready pillars) has some signs of woodworm.


This beam still feels rock solid so I think I've caught it in time and it may even be a historic infestation. I lifted the third board to access this beam so I could treat it, would you recommend lifting the next board as well? I think I can probably just about soak all sides of the beam as it is. My hesitancy is simply not wanting to damage the historic timber more than I have to, the board will split as it's lifted.

The moisture meter isn't calibrated for pine and the instructions mention nothing about calibration. For what it's worth it claims +/-0.3% accuracy in timber although I'm not sure how much I trust that. I'm an avid woodworker so pretty familiar with timber, I would say it's reading ballpark right.

As for when the damage occurred, I can't say for sure but the board that crumbled away definitely wasn't like that 10 years ago. I've done almost all the work on this house myself and I would have come across that and fixed it.

What would you recommend as the next steps? I could lift the whole run of boards but I'm not sure there's much to be gained from doing that. The boards all feel in good shape even though they have clearly been attacked at some point.

 

[CliffordPope]

You can reach a long way into inconvenient places with a lance extension on a pressure sprayer. There used to be kind of "smoke bombs" you could let off in places like underfloor voids which deposited some poisonous substance everywhere. Precautions necessary - always read the instructions!

 

[Lacan07]

So I've lifted three boards to asses the extent of the damage and I'm quietly confident that it's not as bad as I first suspected. The board that tipped me off to a problem was completely eaten away, I pulled it away with my hands.
View attachment 12225
Board number two (the one nearer the camera in photo above) was in rough shape, it fell apart badly enough while lifting it that I won't be able to salvage it. The third board (nearer the camera again) came up but split in the process. You can see the pieces it in the shot above (resting on the treadmill), I've repaired boards like this before. That left me with the hole shown below. I've cleaned and de-nailed (salvaged most of the nails). You can just see a beam running parallel to the floorboards at the bottom of the opening.
View attachment 12226
The joists, as far as I can see haven't been attacked. I'll do another thorough inspection but I'll be treating everything I can reach.
View attachment 12227
View attachment 12228
Unfortunately, the "sleeper joist" (there's no sleeper wall, just a couple of very rough and ready pillars) has some signs of woodworm.
View attachment 12229
View attachment 12230
This beam still feels rock solid so I think I've caught it in time and it may even be a historic infestation. I lifted the third board to access this beam so I could treat it, would you recommend lifting the next board as well? I think I can probably just about soak all sides of the beam as it is. My hesitancy is simply not wanting to damage the historic timber more than I have to, the board will split as it's lifted.

The moisture meter isn't calibrated for pine and the instructions mention nothing about calibration. For what it's worth it claims +/-0.3% accuracy in timber although I'm not sure how much I trust that. I'm an avid woodworker so pretty familiar with timber, I would say it's reading ballpark right.

As for when the damage occurred, I can't say for sure but the board that crumbled away definitely wasn't like that 10 years ago. I've done almost all the work on this house myself and I would have come across that and fixed it.

What would you recommend as the next steps? I could lift the whole run of boards but I'm not sure there's much to be gained from doing that. The boards all feel in good shape even though they have clearly been attacked at some point.

When I first lifted my boards downstairs a few years back I could see little mounds of sawdust on the joist which i assume was the work of the little blighters and that that indicated they were still active

 

[malcolm]

I wonder what's causing the damp the woodworm like. Is the underfloor properly ventilated?

Carpets and underlays are often rubber and waterproof these days which won't help. but wood should be dry enough inside the house when it's ventilated.

 

[Hindsight]

I suspect the problem is that room hasn't been heated but most of the rest of the house has. Water is being picked up elsewhere (upstairs, for example) and then sinking down and settling in the living room. The rubble underfloor is dusty and as dry as I would expect. There hasn't been a carpet in there for 15 years.