Advice please on woodworm

[scoobycrew2004]

Hi all,

We recently started our renovation works on our old timber framed cottage and hit some issues ...some of which were expected, others not.

My contractor has started building our extension (brick) and went to join on to the existing cottage with a wall starter. He peeled back the existing (concrete) render on the corner post and found the post rotten as a pear (see pics). Now to be completely transparent, this was expected to some degree as we were warned of concrete render on timber frame, so part of the project is to peel back the concrete render, repair and replace timbers were necessary and recover with appropriate materials. It's a big job.

However, what we have also found are some woodworm / beetle holes in some of the damaged timbers. My contractor is a little concerned on how we treat these "infected" timbers. It's clear that there are multiple timbers to be replaced where rot has occurred but in the case where we see woodworm holes, should we replace them also as a matter of course or can we just treat them with a spray? My intention was to spray the entire frame once it's all exposed just to be on the safe side but wondered if leaving old timbers was ok if structurally sound.

The other question is, where we replace timbers with tanalised timber will it naturally be protected from woodworm? Or should I take other measures?

Any advice is welcome!

 

[jamest]

To my relatively inexperienced eye, that corner post looks to be in surprisingly good condition. Is it actually soft? Can you push a stiff blade into it by hand? If it's hard, solid timber, it can probably be left as is. This post and the horizontal beams that are visible (tie beams or girding beams) seem to be oak and all look fine in the photo - at least to me.

The stud at the ground floor level that has worm holes in it looks like pine and isn't (seemingly) jointed into the tie beam/girding beam, suggesting that it's a later addition, not part of the original frame. The one at first floor level looks more like oak and could be jointed in (though it's very hard to see).

Most woodworm isn't structurally significant in oak (where most species only attack the sap wood if the wood is dry), but could be structurally significant in soft wood, like pine. There's hardly any worm holes visible though (as far as I can see), so it's not yet a problem, though I suppose there could be larvae in there, in which case keeping it dry is the best treatment - you'll not be able to kill larvae deep in the wood by spraying it.

If it's death watch beetle, that could be a different matter and treatment of some sort and checking for structural defects would be worthwhile. Hard, if not impossible, to tell from photos of affected wood - really need to see the beetles or their larvae.

Anyway, that's probably not a lot of help - might be worth getting a specialist surveyor or timber framer to take a look and advise. Really needs a hands on inspection to be sure. Others on here may have better advice!

 

[scoobycrew2004]

I am informed that the entire frame is pine however, I personally think that there is a mixture of wood types within the frame. I will ask the builder about that beam. These pics were sent to me by him and I'm yet to see it person (stuck at work all week ) but that corner post "blew away in the wind" to quote him.

 

[Matt Green]

It looks to be pine from the photos. The sapwood portions have been faced outwards, there is some furniture beetle damage which is to be expected given the conditions.

Spraying the entire frame is not the best use of insecticide as there may well be no activity (although it's tough to tell from the photos and probably likely there is some recent activity given the circumstances) and there is no point treating heartwood which will be 70%+ of the timber volume and visible surface area. Brush treat any sections with activity that looks recent with a liquid insecticide if it particularly worries you that a few more holes might appear before the structure dries out.

Furniture beetle activity should be quite a way down your worry list from the looks of that exposure work.

M.

 

[aockenden]

Sry, just stopping by to say how cool it is to see the backside of old lath work like that with the lime plaster pushed through the gaps and “hooking” into the backside. What a great system.

 

[scoobycrew2004]

Thanks for the advise (and reassurance) all.

Any thoughts on whether or not the infestation (assuming it's active) can spread to new timbers ? Specifically timbers that have been tanalised/treated ?

Thx

 

[scoobycrew2004]

Sry, just stopping by to say how cool it is to see the backside of old lath work like that with the lime plaster pushed through the gaps and “hooking” into the backside. What a great system.

It is, it's just a shame the previous owners smothered it all with concrete

 

[jamest]

It's always really hard to tell what's what in photos, but if that corner post is pine, then it's probably pretty bad and in need of replacement. I've seen oak frame members that look like that (at least in the photo) and they have been basically fine. The other members look OK, whatever wood they are. I've only ever lived in houses in the UK with oak frames (though the one I'm in right now has elm purlins). I used to live in Queensland Australia and the houses there are like glorified sheds and the frame members are invariably treated pine. It wasn't woodworm that you needed to worry about, but termites - but that's a whole other story.

Anyway. Matt is the expert around here on beetles, decay and what have you. So if he says, don't bother spraying it, that's going to be the best advice. I guess if any members (like the corner post) need to be replaced, it'll be done with treated pine anyway, so no need for more treatment.

 

[Kearn]

I’ll be honest, the running order isn’t quite right. First port of call, understand and assess/repair your existing building. Extensions are things of fancy way down the list…!

Whatever timber lies under that suffocating skin needs to be freed and assessed. And timber can only be truly assessed once all four faces are visible.
Pine would be later bodged replacement timbers, and not ideal for structural framing members. Elm suffers massively from beetle as it munches happily through the entire cross section and with no warning, things go snap. Oak, as mentioned, it’s only the sapwood that gets devoured, the heartwood won’t get damaged (normally. Although we had heart rot on our oak sole plate.

You need a structural view on the entire building, once, carefully freed from its render. Go slowly here, as often the render and infill becomes structural. If it’s all timber framed, you need a conservation structural framer to advise. No one else will come close to

It looks like this place had a Victorian makeover, uniform laths in and out - possibly when timber repairs were undertaken too.

Your builder is out of his depth understandably with timber frames. Dry, low moisture content timber will not be eaten by beetles. No chemicals are required. They also won’t work. And they’re horribly toxic. But it will take some time to dry out once you’ve got the modern muck off.

But all this is from very little info or pics of the over all place…

 

[Cubist]

Any thoughts on whether or not the infestation (assuming it's active) can spread to new timbers ?

It can BUT - logically the burrowing larvae can only transfer into connecting timbers in direct/very close contact. The greater risk is that an adult beetle/fly may choose to lay her eggs in the newly exposed and potentially damp woods but of course seasonal influences to would also be a factor in that case.

All that newly exposed wood should be protected from rainfall in any event and allowed to dry as thoroughly as possible - that may be rather difficult at present though.

This work should not have been started at this time of year.

Specifically timbers that have been tanalised/treated ?

Some of the chemicals used in pressure treatments do aid resistance but its unclear to me whether this is due to its masking the smell of the natural foodstuffs that attract the adult form or if it kills the larva.