Damp and Woodworm in 17th Century Cottage

[katmatt]

We've recently bought a 17th century stone cottage. On the survey it was identified that there was some damp and some woodworm, which wasn't totally surprising. We got a damp surveyor in to take a look and received advice that we should have an injected DPC and needed the woodworm chemically treated throughout the house. The survey was from a company who do damp-proofing and timber treatment, which leaves me a little sceptical that they are simply trying to sell us something even if it it inappropriate.

We don't want to ignore the advice but having read some of the info on damp on this site, we can't see that this is the way forward bearing in mind the age and type of property. We know that there is stuff to do in terms of increasing ventilation as the airbricks are quite small and are about 1 foot below ground level down a little hole!!

Can anyone give some advice on the best course of action on either the DPC or the woodworm?

Thanks

 

[Flyfisher]

We know that there is stuff to do in terms of increasing ventilation as the airbricks are quite small and are about 1 foot below ground level down a little hole!!

I recognise that situation very well. We have a small cellar ventilated by 'underground' airbricks, which had become completely blocked, leading to a damp and musty-smelling cellar. Opening up the vents and leaving the cellar door open throughout last summer completely transformed the situation. The musty smell has completely gone and I'm sure the whole cellar is much drier.

In so many of these circumstances, ventilation seems to be the key factor - that and some time to let the new ventilation do its stuff and for the house to re-adjust.

 

[biffvernon]

Hope you didn't pay that damp surveyor anything.

Don't inject a dpc and don't treat for woodworm.

This is not a good time of year to look for woodworm. If there are any they will be hiding away. Look out in May and June for frass, the fine wood dust that is left by the emerging adult beetle. Only if you find such positive evidence of activity should you contemplate treatment.

As for the damp, it's often best to live in a place for a while to be sure if there is a problem, and then identify what the problem is and then fix it. Just injecting a damp course is a knee-jerk reaction that may do more harm than good.

 

[katmatt]

Thanks for the advice, we'll wait a while and see what happens.

 

[DaveBrigg]

Welcome to the forum Katmatt. Did you notice any damp, or can it only be detected by a meter? If the damp is visible, the best bet is to discover where it came from. Sounds like you've already made a good start with the air bricks. Condensation, leaky or blocked gutters / downpipes, and raised ground levels are common culprits too.

 

[katmatt]

There is no visible damp, it was detected by a dampmeter.

There is evidence of the woodworm though!! I am not sure how to tell if they are still alive, they have eaten their way through the carpet gripper wood to the point that some of it literally disintegrated. However there is no evidence of holes in the floorboards, but we have been told that there is some evidence in the joists. We do not know whether this damage has been done some time ago or more recently, as the carpet has been down for some time. We found some dead beasties within the wood that was left.

Can anyone advise on how we might know if what we have found is recent or old?

 

[skier-hughes]

This is not a good time of year to look for woodworm. If there are any they will be hiding away. Look out in May and June for frass, the fine wood dust that is left by the emerging adult beetle. Only if you find such positive evidence of activity should you contemplate treatment.

This is about the best advice you'll get.

 

[Penners]

If you're lucky, Matt Green will respond to this thread. He's a real expert on such matters.

Meanwhile, a couple of amateur observations (and if Matt disagrees with them, believe him and not me!):

As has already been mentioned, you first need to ascertain whether the woodworm infestation is live or not. But if the property really is damp, then it may be. Woodworm and damp often go hand-in-hand.

The benefit of this is that, if you sort out the damp problem, the woodworm problem can often go away of its own accord.

Damp meters of the two-prong type (eg: protimeter), placed on the surface of the wall, are not a reliable indicator of whether the wall is really damp. The meter may only be measuring surface condensation.

The efficacy of an injected DPC in a stone wall is highly questionable. If the walls really are damp, you're much better advised to pursue a traditional method of damp management - lime plaster, lime pointing, and so on. Search the forum for topics on damp and lime and you'll be inundated!

 

[MdB]

Two prong damp meters measure resistance. They do not directly measure damp. Lots of things will affect the reading such as the as the type of wall, the finish, the amount of salts that have been brought to the surface etc.

Damp in the walls at waist height or higher is very unlikely to be rising damp so an injected DPC won't cure the problem even if an injected DPC works (which is questionable).

If you do have damp then finding the reason why is the first thing you need to sort out. High outside ground levels seems to be a very common problem.

 

[Matt Green]

I've no real need to wade into this thread, the fine posters on this forum have offered sound and useful advise so far, amateurs or not. Unless things look like they are taking a wrong turn I'll keep quiet and not come across like a prig where I can help it.

There is evidence of the woodworm though!!

Whatever is there doesn't warrant two exclamation marks. No house to my knowledge had collapsed due to worm-ridden carpet grippers.

I am not sure how to tell if they are still alive, they have eaten their way through the carpet gripper wood to the point that some of it literally disintegrated. However there is no evidence of holes in the floorboards, but we have been told that there is some evidence in the joists. We do not know whether this damage has been done some time ago or more recently, as the carpet has been down for some time. We found some dead beasties within the wood that was left.

Can anyone advise on how we might know if what we have found is recent or old?

Follow the advice given: clean the surfaces as best you can and check again later in the year. Look for high ground levels. External ground levels should be a minimum of 150mm below finished internal floor height. Any less than that and there is a risk that ground water will move through the base fo the walls (and the joists ends that are in/next to them) and into the room.

Carpet gripper rods are made from some of the cheapest timber imaginable: they are predominantly sapwood (the outer part of the tree). Roughly speaking the more sapwood there is in a piece of timber the cheaper it is and the more susceptible it is to insect attack. Your floorboards are better quality (less risk) and your joists are better still (even less risk), but where they are in direct contact with wet masonry the risk increases.

What beasties have you found? What do they look like- beetles or larvae (grubs)? From what you have said so far, it sounds like the damage is from wood-boring weevils rather than furniture beetle.

Best of luck. Don't panic.


Matt