Woodworm advice needed

[housewinnie]

That last pic looks like most of our joists and rafters in our house. I wouldn’t worry about that. You could get a small de humidifier. We run one for a few hours every night and takes away the condensation and throws out some warm air too.

 

[Hindsight]

Well now I feel silly. We have a dehumidifier, it didn't cross my mind to use it in there. I much prefer to use ventilation where possible but I suppose this room needs a bit more.

 

[Toby Newell]

Yes, use a dehumidifier and a little more heat. As Matt says, unless you soak the boards and everything in permethrin the beetle won't die until they complete their lifecycle.

Your little bits of slate under the seat joist aren't 100% great, they look jagged and bitty and will hold condensation. It doesn't look that bad. If you must use permethrin then just use it in the very local area on the joist, no need to treat the new boards.

 

[Toby Newell]

For example, the worm is pretty bad in the boards but the joist look better, if you had wicking damp it would be the other way around, I see joist that crumble to powder.

To me this indicates a high RH atmosphere, either through poor ventilation or lack of heat.

 

[Hindsight]

Excellent, thanks.

Oddly enough there's no evidence that I can see of beetle activity in the joists except just by that piece of slate. Do you think it's worth knocking it out and replacing? As far as I can see the brick is just resting on the ground so it would come out easily. I've got DPM to separate the beam from the ground.

I'll be giving the joist and boards a good coating of permethrin, I think. Would it be worth sanding the floorboards before application to aid uptake? They have had some sort of finish applied at some point, maybe wax. The plan, one day, was to sand and refinish the whole floor, I've not got around to it yet as there's always something more urgent to fix.

 

[Matt Green]

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.

What would you recommend as the next steps?

Nothing? I haven't seen anything that suggests this is an active infestation. Vacuum thoroughly and maybe screw down any replacement boards for a year or two to make future inspection easier to check for new bore dust (frass).

 

[Toby Newell]

Excellent, thanks.

Oddly enough there's no evidence that I can see of beetle activity in the joists except just by that piece of slate. Do you think it's worth knocking it out and replacing? As far as I can see the brick is just resting on the ground so it would come out easily. I've got DPM to separate the beam from the ground.

I'll be giving the joist and boards a good coating of permethrin, I think. Would it be worth sanding the floorboards before application to aid uptake? They have had some sort of finish applied at some point, maybe wax. The plan, one day, was to sand and refinish the whole floor, I've not got around to it yet as there's always something more urgent to fix.

Yes, as Matt says, remove damage, replace, increase heat and ventillation and wait. Lower moisture content will make future infestation much less likely. As an example, I see dozens of floors with worm damage per year, some old country cottages from C.15th. The average number of times I use permethrin is zero.

I think I used it once last year on a small area in a Hertfordshire cottage where the joist were laid direct to the ground.

And yes, I raised them on engineering bricks, coated the new joist and noggin areas in blackjack bitumin primer and stuck bitumin flashing tape to all touching areas as my dpm.

So yes, I would isolate supports with dpm to ground and replace slate, it can't hurt.

 

[Lacan07]

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.

If your sub floor is nice and dusty this time of year your doing well, wish mine was.

 

[Hindsight]

If your sub floor is nice and dusty this time of year your doing well, wish mine was.

As long as I stay on top of the maintenance tasks this place is reasonably good in terms of damp, heating, etc. It's a labour of love though and I fell out of love with it about 5 years ago. The job I really hate is climbing out onto the roof to clear the gutters. We've got an idiotic design where the front gutter drains to the back of the house through the loft. When the moss builds up the house floods! I believe it was a fairly common design on Georgian properties to keep a clean front aspect.