Woodworm - advice deeply appreciated....

[Turiya]

Greetings. Thanks for taking the time to read this.
Have recently joined the forum… have been reading some of the historical posts for insight. Purchased an 1870 ish cottage at the start of 2020. Knew historically that it had had big issues with condensation, could drip down walls etc, PIV system was put in. There are localised damp patches near the base of some of the downstairs walls, worse on internal walls and were tide marks on the chimney breast and walls close by. My surveyor was not unduly concerned and an experienced period plasterer told me to let sleeping dogs lie. Ground levels at the front are somewhat too high so need addressing. The property had been empty for 15 months prior to completion and I was not able to be there much for the first couple of years so heating was left low with not a great deal of ventilation. Not great I know. My big concern is that I believe woodworm has taken hold in areas, not just common furniture beetle but possibly death watch…think I have seen a few of the latter wrapped in spiders webs. I saw some rather decaying wood in the corner of the property when I looked round but didn’t think twice about it. I have had a few firms round to assess, lift floorboards, look in the loft and there appears to be disagreement. There was a couple of patches of frass found on the loft timbers which was highlighted and some floorboards were lifted as I had felt sagging… certainly edges have been lost in places, there are some fresh holes and there seemed to be some frass. The recommendation was spraying and damp course injections and cement etc which on reading your helpful posts and listening to Peter Ward I know not to do. I a grateful for reading the previous posts that elimination of moisture in the timbers / relative humidity is key. The main external beams in the downstairs rooms are painted so will retain more moisture. The meter was reading 12.6 a few weeks ago and 9.6 a few days ago. I know this is not a very deep reading in the wood though….am thinking about beetle’s preferred environment. A few questions if I may for any resident specialists… Matt and others…?

• If an infestation took hold when the moisture in the timbers was much higher for a few years but then this is reduced, what happens to the eggs and larvae? How low does the reading have to go and for what period of time for both death watch and common furniture beetle larvae to die or do there just go dormant and can be ‘reanimated’ many years later if the moisture level increases again?
• In respect to the floorboards upstairs, if I have a number of them lifted for a couple of months to increase ventilation to the joists etc and keep tabs on the moisture readings, could this work in killing off the infestation?
• I have seen a couple of what may be dead long horns (not the classic house one but large, different colour and similar body construction). Does the same logic apply for them in situ in respect to reduction of timber moisture below a certain point…?
• I know the fallacy of so called moisture readings on walls but if, where the main oak beams enter the walls, shows green on the machine, are the ends in danger ? (one does meet an external wall).
• Would I need to increase ventilation in the loft to combat the small outbreak there? Currently have soffit vents for that and insulation down.
• Been looking for pheromone traps for both types of beetle to little avail. Any ideas and would this be useful…? Am a bit reluctant with general glue traps as may get the spiders, indeed any other life, as well.
• Excuse the ignorance, but how do you ventilate the subfloor void at an upper level if no external ventilation bricks ?

Will certainly try and round up as many spiders as I can to put in the property ;-) Any and all thoughts gratefully received… have had quite a few sleepless nights and anxiety and do not want to use chemicals.

Many thanks.

Turiya

 

[Toby Newell]

Hi

Try and find a trusted and experienced damp guy and take it from there. Good surveyors are hard to find, same with damp guys. As a curveball, consider contacting a good timber framer, think of a surveyor as the owner of a GP team and the timber framer as a chief mechanic, the latter knows exactly how everything works in theory plus actually how everything works, whilst the former thinks he knows everything, yet rarely does.

Your surveyor and plasterer don't seem too bright if indeed you have beading water inside your house. Just one question, did your experienced period plasterer do any work in your home? If so did he use lime? And did he comment if the rest of the plaster was lime or gypsum? Depending on the answer you can add to the bottom of this comment that if things don't improve by Christmas after trying some of the things I mentioned, then you might consider checking if your walls have been replastered in gypsum and or had non breathable paint applied.

In general beetle larvae like wood RH 12%+ at low RH they die out, no need for chemicals. I have restored and repaired timbers in several hundred period properties and only ever had to use chemicals on a handful of times, it really isn't great stuff to have in your home. Besides, if you want it to work properly you would need to remove all the floors and coat all the joist / beams, which could cause a lot of damage if not done very carefully.

I would undertake all reasonable remedial steps first, PIV is a great start, lower the raised ground level outside asap, consider putting in French drains. Remove the exterior coating to the beams and recoat with microporous stain - not a priority (Sikkens is good for stains or Ingilby for paints) Actually removing non breathable paint, if any, to the masonary might have greater effect. Check to see water not coming in chimney! As regards your questions:

Life cycle can be 3 to 5 years, no need to treat though if moisture level reduced, larvae only killed if they munch exterior wood in contact with pesticide, so if gallery not exposed, it won't have much effect. In places like USA and Australia where they have much more serious problems they cover entire house in tarps and fumigate. Solve the damp issues and forget about them, they will soon die.

Longhorns are very pretty! They tend to like outside timber and nectar, if they munched your beams you would know it! Their exit holes are 5mm + don't worry anout them inside, unless you have a large log pile.

OK. Forget the 'machine' they are likely as useless as a weather app as you are looking out the window, next time get the make and model and ask how much they cost. An impedence spike meter only measures the moisture level at the spikes. A proper reading is taken when probes are inserted into the middle of the timber, a quality Protimeter with deep probes is £500 to £800. For a proper survey you also need at least one hygrometer to work out where the moisture is coming from. (More correctly if there is a large difference in moisture level) These are normally £300 to £2,000, the more expensive ones can track readings over time and stream to a BT receiver or Wifi network. Ideally, even for timber readings you want to use a hood hygrometer in the room for a minimum of 48hrs to allow the RH readings to reach a steady state and then compare the two, that can tell you if the wood is damper than ambient or vice versa, as in general RH readings equalise if there is not a serious issue. Cheap £30 probes are useless toys, that cannot tell you more than eyeballs or a well calibrated hand.

Make sure you have enough soffit vents and they are unobstructed.

Also check if any work has been done to the roif.

Am pretty sure pheremone traps are pointless.

Heat rises, water vapour is lighter than air, thus it will eventually rise and go out the roof space. Removing any floor coverings will help this.

In general keep house at a minimum temperature, you have a PIV so either crack a few windows if you haven't had trickle vents installed. Open windows in kitchen / bathroom / utility room better still install fans and try and hang laundry outside where possible.

Common furniture beetle aren't a great issue, powder post and death watch more so, but only if left to munch for years, most frass is old, its hard to tell if not in person, frass ages just as wood does at first it is a whiteish cream which slowly turns more yellow, impossible to tell in a photo. All 3 are incredibly small, a large common furniture beetle (the smallest) looks like a small death watch, although death watch can be 4x the size, powder post are around 2x the size and more brown and shinier. CFB flight holes around 1 - 1.5mm, PPB around 1.5-2mm and DWB around 3 - 4mm.

Whilst I certainly may want to delay moving Aunty Mavis' Sheraton sideboard into the house I certainly wouldn't overly worry about the wood worm. I would continue to gently worry about the damp issues and try and get to the bottom of that and the wood worm will simply go away.

If it was me I would advise 1. Check you have cover pot on your chimney! 2. Remediate excess ground level outside asap. 3. Fit trickle vents if none and / or leave windows cracked. 4. Keep house heated reasonably 5. Check guttering and drains. 6. Wait until the end of the year to see if problems improve, they almost certainly will, it will take a few months to dry out. If things are still not great then consider 7. Installing extractor fans to help the PIV and 8. Digging French drains (although this may prove cheaper to do this when reducing the ground level)

At no point would I consider using any pesticide chemicals (or drilling holes and inserting DPC) unless you start hearing DWB ticking sounds and see piles of fresh frass all over your furniture.

I am not saying your DPC has not been compromised and that having DPC pumped in would not help, but it should be last on the list of remedies and not the first as it might not help at all and besides it's pretty easy to do yourself.

Low quality people tend to profer it as a quick solution as a trained oranutang can charge several hundred pounds if they can hold a drill and a hose steady for a few seconds.

Best of luck.

 

[Toby Newell]

FYI, this is the worst of four1550 floors I just finished in Kent. OK, so in all fairness if there were any little critters still alive they probably didn't like the amount of wood hardener and filler I applied... but still, no pesticide.

 

[Matt Green]

Hi Turiya

My big concern is that I believe woodworm has taken hold in areas, not just common furniture beetle but possibly death watch…think I have seen a few of the latter wrapped in spiders webs.

If you are seeing adult beetles, it's a good idea to take into account their lifecycle and rewind back to when the eggs would have been laid and consider what might have changed. Furniture beetle go through their lifecycle from egg to adult in between 2 and 5 years. Two years is the timber is cheap as in has a high proportion of sapwood, the outer part of the timber that is high in nitrogen and high in water content; five to ten years for deathwatch beetle.

I saw some rather decaying wood in the corner of the property when I looked round but didn’t think twice about it. I have had a few firms round to assess, lift floorboards, look in the loft and there appears to be disagreement. There was a couple of patches of frass found on the loft timbers which was highlighted and some floorboards were lifted as I had felt sagging… certainly edges have been lost in places,

That checks out. When timber is planked from the trunk, sapwood is on the edges of the planks:

I am grateful for reading the previous posts that elimination of moisture in the timbers / relative humidity is key. The main external beams in the downstairs rooms are painted so will retain more moisture. The meter was reading 12.6 a few weeks ago and 9.6 a few days ago. I know this is not a very deep reading in the wood though….am thinking about beetle’s preferred environment.

It is key, and that is pretty dry. On the edge of what beetles could chew through.

A few questions if I may for any resident specialists… Matt and others…?

• If an infestation took hold when the moisture in the timbers was much higher for a few years but then this is reduced, what happens to the eggs and larvae? How low does the reading have to go and for what period of time for both death watch and common furniture beetle larvae to die or do there just go dormant and can be ‘reanimated’ many years later if the moisture level increases again?

They die within the timber. They can't reanimate, zombie beetles would be terrifying and Britain's housing stock would have been reduced to dust years ago. Essentially what the water is doing is making the wood cell structure softer and easier to chew through. There are other characteristics that can also affect wood hardness including the rate of growth for example, in that fast grown trees have bigger cells and are softer- cell walls provide the strength and hardness to the wood. The lower the cell wall to cell volume ratio, the softer the timber.

Therefore....it's to give an absolute figure for moisture content and susceptibility to attack. Sub 10% is good odds though.

• In respect to the floorboards upstairs, if I have a number of them lifted for a couple of months to increase ventilation to the joists etc and keep tabs on the moisture readings, could this work in killing off the infestation?

It's pretty marginal. Vacuuming the joist voids would certainly help in aiding air movement and act as a baseline for monitoring future activity.

• I have seen a couple of what may be dead long horns (not the classic house one but large, different colour and similar body construction). Does the same logic apply for them in situ in respect to reduction of timber moisture below a certain point…?

Indeed but they are not eating your house, only your firewood.

• I know the fallacy of so called moisture readings on walls but if, where the main oak beams enter the walls, shows green on the machine, are the ends in danger ? (one does meet an external wall).

It's not a fallacy so much as knowing what you are doing if you use a resistance meter on plaster. It's a good tool frequently misused. For the beam, yes the bearings are likely to have a higher moisture content than the span. The paradox of chemically treating timber in situ is that the areas most at risk are the ones you can't get to. If the bearings are wet it suggests you have a guttering problem or that rainwater is being held in the masonry in some fashion

• Would I need to increase ventilation in the loft to combat the small outbreak there? Currently have soffit vents for that and insulation down.

I would be inclined to vacuum up the frass and make a decision whether or not to brush treat a tiny amount of insecticide on the affected areas next year.

• Been looking for pheromone traps for both types of beetle to little avail. Any ideas and would this be useful…? Am a bit reluctant with general glue traps as may get the spiders, indeed any other life, as well.

They work fairly well as monitoring tools in confined spaces. You are looking for a pheromone called stegobinone (2,3- dihydro-2,3,5- trimethyl-6-(1-methyl2-oxobutyl)-4Hpyran-4–one

Hiresis Biscuit Beetle Lure

A biscuit beetle (Stegobium paniceum) pheromone lure to aid detection and monitoring of this important stored product insect. The tablet needs to be placed onto a sticky pad and used with either the AF Insect Monitor or AF Demi Diamond. It is recommended that the tablet and glue pads are...

catalogue.killgerm.com

It's usually marketed for the monitoring of Biscuit beetles (Stegobium paniceum, hence the name) but will work for a number of different anobid beetles including furniture beetles. It still needs a sticky surface to hold the beetles, which means a risk to spiders.

• Excuse the ignorance, but how do you ventilate the subfloor void at an upper level if no external ventilation bricks ?

By cleaning and not laying fitted carpets. That's all. A lack of ventilation never causes attack by furniture beetles but will prevent drying if timber with high sapwood content become wet and remain wet.


Matt

 

[Toby Newell]

I would add, as far as I have seen, I think deathwatch prefer oak, common furniture beetle prefer pine, unless the oak is really damp. If your beams are oak then as Matt says it's mostly the sapwood that goes, tje heartgrain is normally fine.

 

[Turiya]

Deep thanks Toby and Matt for your advice. Much appreciated.

The walls are gypsum... hasn't been treated like a period property in the past. The plasterer who came round to give advice didn't do any other remedial work and with the damp specialists I have spoken with, none of them suggested reworking with lime, just the usual cement mix after injecting a DPC. Unfortunately can't take on the work of cleaning the beams at the moment of paint and know there is a debate about the best method, whether soda blasting or other. The chimney is watertight.

You mentioned keeping the house at a minimum and reasonable temperature. Currently it is set to 20... will this be ok? Presumably with damp and salt issues, such a temperature will increase humidity. Will buy a RH reader to monitor as this will effect the temperature and how hospitable the beams are for the critters. Certainly the upstairs is much colder than the downstairs as possibly not enough radiators and the boiler seems underpowered for the size of the property. Windows are cracked as no trickle vents. Thanks for the advice about outside ground levels. Thanks for the pictures you sent of the restoration work... quite a transformation!

Matt - is it completely impossible for a DWB to mature and exit before 5 years...? Have read conflicting things on this...
How long would a particular RH have to be maintained within the timber beams for eggs and larvae to die?
Anything else I can do if they are nibbling the floorboards..?
Do other long horns not take root in household timber then... just surprised that Hylotrupes bajulus is the only one really focused on.

Many thanks...your input is much appreciated.

T.

 

[malcolm]

I wouldn't worry about what type of beetle you have. As has been said above beetles aren't a problem in dry wood. Trick is letting the wood dry out.

The exact percentage of dry I don't know, but houses have survived for hundreds of years and they didn't have central heating back then so it probably doesn't need to be all that dry. Doing sensible stuff and central heating is bound to work.

The trouble is normally modern waterproof paints. Gloss paints are bad and emulsion paints are pretty close. Water comes up from the floor and can't get out past the paints and over many years the wall gets soaking wet. I was surprised to find damp halfway up a staircase that had no issues other than modern paints. Fortunately there was no wood in that wall.

The basics are external ground levels lower than internal ideally by 6 inches. Exterior wall should be breathable and not be covered in cement and waterproof paint. You'll need to fix gutters and blocked drainage too.

For internal walls you can still get trouble with damp and at least the bottom 24 inches of one side of every wall ought to be breathable. So lime and a clay paint.

Photos would help a lot.

 

[Toby Newell]

I would defer to Matt on this one, I just repair the damage and fill the holes! I think Matt is an expert on the little critters! I don't think I have ever seen DWB, maybe one or two CFB and a few Post beetle who crawled out the galleries and died when I injected pesticide into them on some furniture with a needle, I felt bad!

All I can say in general, having seen hundreds of homes with worm damage and having dozens of repeat customers, once the home is dry and heated they die but having been unheated so long it is perfectly possible you have some live colonies.

Whether or not you would want to treat with pesticide I defer again to Matt, as far as I know it's a contact poison so you would need to remove flooring and coat as much of the beams as possible.

You may have a legitimate case to use some pesticide in the interim, but long term once you have improved the damp situation as Malcolm says they will eventually die, so resolving the damp issue is no 1 priority.

Not sure you need to heat to 20C long term but higher temperatures will help drive off the extra moisture you have accumulated as will more air movement.

It's not just ambient temperature per se, its also RH, relative humidity. The amount of moisture in the air at a given temperature is sometimes referred to as 'dew point'.

Just like only so much salt or sugar will dissolve in water, only so much water vapour can be held in air, once the humidity reaches 100% water starts to condense, or form 'dew'.

At higher temperatures (higher dew point) the air can hold more water, so warmer air can actually be more humid than colder air.

Keeping things warm will reduce condensation (and drier wall and floors are more insulating) but you also need air movement to transport this expired moisture outside. Your PIV system is a great start, as long as you leave gaps where the air can escape.

Heating and ventilation is no 1 as that is easy to do and will help no matter what, then it's a case of noting over time how much things improve. Roof / guttering are goid places to start, as is lowering obviously high ground levels outside, these should not break the bank. Then maybe you could look at making your walls more breathable, if you still have issues.

 

[Matt Green]

You mentioned keeping the house at a minimum and reasonable temperature. Currently it is set to 20... will this be ok?

More than enough

Presumably with damp and salt issues, such a temperature will increase humidity. Will buy a RH reader to monitor as this will effect the temperature and how hospitable the beams are for the critters. Certainly the upstairs is much colder than the downstairs as possibly not enough radiators and the boiler seems underpowered for the size of the property. Windows are cracked as no trickle vents. Thanks for the advice about outside ground levels. Thanks for the pictures you sent of the restoration work... quite a transformation!

Ground levels are responsible for a great deal of water movement and timber decay in period properties, the effect of living inside a house before and after reduction is equally transformational- it feels less damp.

Matt - is it completely impossible for a DWB to mature and exit before 5 years...? Have read conflicting things on this...
How long would a particular RH have to be maintained within the timber beams for eggs and larvae to die?
Anything else I can do if they are nibbling the floorboards..?
Do other long horns not take root in household timber then... just surprised that Hylotrupes bajulus is the only one really focused on.

Right then. Let's explore the world of variable factors that influence a wood-boring beetle's life history- there's nothing people like more than a definitive statement and there won't be any of those in this response...

1) No, but the timber would have to be very poor quality oak (usually) with a lot of sapwood and be uniformly wet at about 20-25% moisture content for DWB larvae to get enough energy inside them to pupate. I might be able to do it in the lab if I was trying. The odds are low enough that you don't need to lose any sleep.

2) For which: timber species, timber quality, rate of growth, beam dimensions and surface area, number of cracks and shakes, depth of egg laying and environmental conditions will affect the outcome. Hmm.

How about this for Scots Pine as a starting point:

Oak won't be much different but is more dense and will take longer to dry, particularly if covered in paint (see Malcolm comment about waterproof paints, they are waterproof in both directions unfortunately)

"One good summer if water can pass through the surface unimpeded" is a good rule of thumb.

3) They probably aren't- it's extremely likely to be historic damage. Clean up and repair having read Toby's posts. Pictures always help though, post some up if you get the chance.

4) House Longhorn, Hylotrupes bajulus, is rarely a problem these days. The larvae are big enough to chew through relatively dry timber compared with other UK wood-boring beetles and other species of longhorns. They are a rarity. Other UK longhorns are forestry pests that leave the timber post harvest when it starts to dry down. Very pretty though.

Many thanks...your input is much appreciated.

T.

No problem. Keep in mind that tearing apart you house to kill insects is likely to do more damage than they are doing.


M

 

[Turiya]

Apologies for the delay in acknowledging your responses - didn't receive notification. Very much appreciated, thank you.

Have taken serious note about the exterior ground levels... will check out a few videos and see if I can do what is required myself. Standard acrylic / emulsion paints are throughout from previous owners and also on the exterior. Have been watching a number of Peter Ward videos about damp in general and about removal of exterior paint - quite a big undertaking. In the interior I imagine it means removing paint/ plaster back to brick, lime plastering and then painting... apologies, am completely new to the world of DIY / renovation. Thanks for the dew point information. Must be a fine balancing act to have a damp property, heat it via central heating to dry it out but get the ventilation balance correct so as not to build up greater humidity that then effects the timber. I was told by a damp person (his professional credentials rather than personal observation ;-) that for a PIV system to be effective it worked on a sealed unit basis...windows were better shut in the vicinity...?

The house was unoccupied with no heating for around 15 months I believe before purchase and then for quite some time I had the heating on very low so I imagine a foothold was gained then. Unsure if a cold cottage could have produced moisture content in the painted beams of 20 -25% for DWB to take hold or if this really gets to this level only by water ingress / saturation. Thanks for your reassuring words thought...

Read about a great trial they did with a beetle infestation and the introduction of spiders...

One quick question... if I have a moisture meter and it has various wood settings to customise the reading, but I don't know what the wood type is, what is the most advantageous way to proceed...?

With continued gratitude.

T.

 

[Matt Green]

Unsure if a cold cottage could have produced moisture content in the painted beams of 20 -25% for DWB to take hold or if this really gets to this level only by water ingress / saturation.

It would need a source of water beyond atmospheric.

One quick question... if I have a moisture meter and it has various wood settings to customise the reading, but I don't know what the wood type is, what is the most advantageous way to proceed...?

Identifying the timber is the best bet. Clean up a bit of end grain and take a picture with a macro function. Oak looks like this:

 

[Feltwell]

What time of year do furniture beetle burrow out of wood and fly off Matt?

I finally got around to treating my pine cellar steps with permethrin, the only place I'd use the stuff really but it will always be damp down in the cellar - though since I fixed the drain outside the airborne humidity has dropped from a consistent 70% to around 60%. I painted the steps so I can see if any new flight holes appear - so far so good.

 

[Toby Newell]

I have only seen them around now (furniture beetle) actually from around Easter, so spring / early summer. Mind you, the ones I saw around Easter were probably powder post and that was in Tuscany, so a little warmer than the UK.

If you treat any galleries with a hyperdermic needle around the time they pupate you can possibly see them crawl out and die. It's very rare to see them though, unless you specifically see fresh frass.

 

[LadyArowana]

unless you specifically see fresh frass.

Reminds me of the time I watched an unidentified tropical bug cause a tiny dribble of dust to exit a little bore hole in the kitchen worktop of a holiday place. Several mornings I had wiped up tiny heaps of what looked like sand, that time I saw it happen. Very humid climate and a place everyone accepted that bugs happen and not to stress about it.

 

[Matt Green]

What time of year do furniture beetle burrow out of wood and fly off Matt?

I finally got around to treating my pine cellar steps with permethrin, the only place I'd use the stuff really but it will always be damp down in the cellar - though since I fixed the drain outside the airborne humidity has dropped from a consistent 70% to around 60%. I painted the steps so I can see if any new flight holes appear - so far so good.

Rules of thumb-

Furniture Beetle: April until end of June
Deathwatch: Late March until early May

 

[a twig]

Annoyingly I have furniture beetle in my Chesterfield wingback chair, up in the headrest area, which I can hear just next to my left ear when I'm sat in it. I can't get at the wood without fully stripping off all the leather, so instead just going to hope the beetles die before the structure of the chair gets compromised