Woodworm in floor joists - red dust

[OhGranny]

Hi
Been under my floorboards.
I have found what appears to be woodworm in 2 floor joists. I noticed two piles of red dust and the joists have been eaten where they sit in the sockets in the wall.
No other joists seem affected but I have taken the 2 joists out - fortunately they are very short ones between the chimney breast and outer wall.
I think the cause is that the cavity is full of crap in this corner and it is damp. I have knocked a brick out and cleared the cavity as much as I can before I put new joists in.
Now questions? If anyone can help.
If it has eaten about 6 inches along and about an inch of floorboard on either side how long approximately will it have beeen infected?

Should I treat all the floor joists and floorboards now or will taking out the two affected joists be enough?
The reason I ask is I have rockwool insulation under the floorboards and it will be a hassle to get it all out to treat the floorboards and joists.
Any advice on the best treatment.
Thanks and am I glad I noticed it in time (hopefully)
G.

 

[Joe Malone]

What makes you say you have woodworm? Have you got exit holes (about 1.5mm in daimeter) and frass have you actually visual identified the beetles or larvae?
The red dust that you mentioned makes me think that you've actually got an outbreak of dry rot under there. If it's rust coloured dust then likelihood is that these are spores eminating from a sporophore (fruiting body). Unfortunately damp timbers are susceptible to dry rot and woodworm, the larvae like a little gravy with their food. Primary treatment measures for dry rot should always be to eliminate the source of damp, promote rapid drying and increase subfloor ventilation. I find this almost always works without resorting to chemical treatments. You'll obviously have to cut out all infected timbers if this is the case and you should aim to replace timbers upto 1 metre past the last sign of infection.
If you have got woodworm then it's wise to identify whether you have a live outbreak. Thump the timber holding a paper underneath, if frass falls out onto the paper then this indicates a live outbreak. Frass is similar to sawdust but will feel slightly gritty like fine sand the woodworm larvae leave tiny elipsoidal pellets just visible to the naked eye. Another good trick is to use a water based adhesive to stick a piece of tissue paper over the exit holes. The adult beetle emerges from the wood in June or July and will make holes in the tissue paper as they burrow through. If this doesn't happen then it's unlikely that you have a live outbreak.

 

[OhGranny]

Thanks Joe
Think may have combination of dry rot and woodworm.
There are definitely round holes about 1.5mm but they appear as long slots with rounded ends along the grain - up to about 15 to 20mm long.

Tapped the piece of wood and loads of reddish dust came out, the timber is all cracked and frail at the ends, you can crumble it with your fingers but couldn't see any larvae even with a magnifying glass.
So no visual identification.

This is an ex local authority house and they did a wall tie inspection a few years back and the cavity has been blocked by the numpty's knocking all the rubble through into the cavity instead of pulling it out.
The ends of the timbers in this corner have been sitting in damp rubble and lime mortar.
I have taken a couple of bricks out in the very corner and cleared the cavity above damp proof level and as far down as I can reach where the timbers sit.
Thing is, the house two doors away was evacuated a couple of years ago because they found woodworm.
The next tenants also had a understair floor collapse on them because of woodworm - so I think it is in the vicinity.
Mega worried !!!!

G.

 

[Joe Malone]

It does sound like woodworm, the larvae always burrow along the grain. It's worth defrassing to see how deep into the timber the damage goes. Quite often it'll only affect timber near the surface and won't have a huge impact on the integrity of the wood. Just pare away at the timber near the exit holes and see how deep the damage goes.
Have you found a fruiting body under the floorboards? You'll have a mushroom smell and a large flat round platelet type fungus somewhere. The red dust doesn't make sense to me unless you have one of these somewhere.
From you you tell me about the timber I don't think you've got an active outbreak of woodworm. They have about a 5 year lifecycle.
Just replace the damaged timbers and take the course of action that I recommended earlier. The best thing you can do is to increase the subfloor ventilation and make sure you don't have any sources of damp. Once the timber moisture content comes down below 20% then you'll control both conditions naturally.

 

[OhGranny]

Hi
No fruiting body or mushroomy thingys!
Thank god.
Let's go back a bit.
We were told we had rising damp - been through all the driling and chemical injection etc. - but many thanks to cwatters on ebuild (sadly can't find link anymore) for sorting out source of "rising damp".

No rising damp - Problem - High relative humidity in underfloor space due to scaped earth floor surface and two courses of brick under wooden floor above DPM, - wicking moisture up through inner course.

I laid builders membrane over the scraped earh surface and along with air bricks this has reduced the underfloor humidity and cured the "rising damp" .

It is the membrane on the scraped earth floor that has shown up the lines of red dust which makes me suspect woodworm and the dry rot due to the ends of the floor joists being soaked in their cavities.

Also the walls of the under floor space are full of a furry white coating and it is has a musty smell.

What is this white coating - Is this the dry rot?

Will fungicide treatment kill it?

Am I in deep S**t ?

Many thanks


Open to all advice

G.

 

[Joe Malone]

The white furry thing you describe sounds like the dry rot mycelium or hyphae. The mycelium is the main body of the fungus and is normally a silky grey appearance, it throws out feeder strands or hyphae which sounds like what you describe. The reason dry rot is so dangerous is that the hyphae have the ability to grow over inert materials such as brickwork and plaster until they reach a new food source. Quite often they'll even spread behind the plaster. You're not necessarily in deep shi*, that will depend purely on how much damage has been done to the existing timbers. Do whatever you can to increase sub-floor ventilation; i.e, installing extra air bricks then monitor the timber moisture content over the next six months, providing moisture contents are below 20% then you've got nothing to worry about, the dry rot will just lie dormant below this moisture content and cause no further damage. Get yourself a cheap moisture meter and after doing what I said you should be fine. This problem is easier to sort out than you imagine. The main body of work may simply lay with replacing damaged timbers.

 

[roy c]

Joe knows what he is talking about on this subject, I worked in Guernsey for a long time doing Dry-rot,wood-worm treatment and damp-proofing. I seen some real horrific scenarios caused by dry-rot. All were treatable, now the chemicals used are a lot safer than when I was using them. Most were carcinogenic (Murosol) was one that we added to 20 litres of water and then injected into the masonry and then surfaced sprayed with it. It contained TBTO, which was used for clearing algae off the bottom of boats but was banned in the 80s because of the hazard to marine life!!! Also a lot of the "fluids" contained Lindane which was another bad one.. But I agree with everything that Joe says and would also look up Sovereign Products, as they are very good for the treatment of wood-worm and all wood rots..I would recommend when you put back your new timber, make sure it is "Tanalised" and also use a preservative "Paste " on the ends if they are going back into the walls. As for the "Tendrils" of Dry-rot I have seen them find their way thru concrete to get to timber to feed on the cellulose in the wood.. So I think you don't have to loose too much sleep with your problem, Dry-Rot cannot exist if there is a good "Air-Flow"......

 

[gregers]

blimey roy you didnt work for the same company as me did you?i used to use murosol and others that contained lindane,

granny phone up your local preservation firm and get them round for a survey then decide whats the best thing to do.

 

[Joe Malone]

Roy's right, use tanalised timbers and if you're replacing joists which are sat in brickwork then make a 'boot' for the joist end using a roll of polyethylene dpc. If you want to use chemicals which personally I don't think you need then Boron is the way to go.

 

[OhGranny]

Hi Everyone
I found one of the blighters in the old joist end.
Looks like it could be the furniture beetle. Rather long Thunderbird 2 !!

The white on the bricks is more crystal like than mould - looks like it could be salts that have leeched out over the years possibly drawn up through the bare earth, there was a strong ammonia like smell before I put down the builders sheet.
I am putting in an extra air brick.
There are bore holes in the edge of one floorboard about an inch either side of where the joist was and about an inch wide - should I replace that or could I treat it?.
The floorboards are sanded and varnished so I would like to treat rather than cut a piece out if possible.

Many Thanks

 

[JohnD]

pictures! pictures!

with a coin or measure to show scale

//www.diynot.com/forums/viewtopic.php?t=129539

 

[roy c]

gregers Posted: Sun Jun 08, 2008 12:53 am Post Subject:

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blimey Roy you didnt work for the same company as me did you?i used to use murosol and others that contained lindane,

When I worked with these chemicals you had to be a registered "Treatment Company" and only you could get the chemicals. I think Murosol was made by Cuprinol, we were supposed to wear a mask when we were injecting the masonry (10mm holes drilled every 8-10 inches apart all over the wall at a depth of about 16 inches) the walls were usually 20 inches thick!!! But we would light up a fag, have our lunch in the room and stupid things like that. We were not informed of the highly dangerous nature of these chemicals. When I found out from a friend of mine who was a safety officer he told me to get in touch with the company providing the chemicals and get a safety leaflet. I had a reply from them saying there was no danger if used properly...... I them went to my boss and told him I wasnt working with them chemicals again, he said "Ok get the labourer to inject and spray them!!!!!!" Time to move on and one of the lads I worked with died young and the Boss has had a triple heart by-pass and is not well at all!! This was1986 and I moved from Guernsey to where I am now and they were selling Murosol over the counter at the building suppliers, a few months later it was took off the shelves, never to be seen again and replaced with "Low odour Environmentally friendly Injection fluid" Don't do much of that work now!!!

 

[Joe Malone]

OK,heres a description so you can check it against what you've found.

Beetles are 3-5mm long, Thorax hood over head, Squat body of reddish brown colour. Rows of small pits on wing cases. Last 3 joints of antennae larger than the others. If you've got a magnifying glass you'll clearly see what I describe if it's a furniture beetle.