To treat woodworm or not?

[FamilyWiggs]

I'm replacing some of the floor joists & floorboards in my 16thC Welsh farmhouse.

There is evidence of past woodworm in some of the timbers & floorboards. Nothing ongoing now though, from what I can tell.

I've put in air-dried oak timbers, but the floorboards are modern softwood (expense and they'll never be seen being the considerations here).

Should I treat the new oak joists and/or floorboards for worm? I'm thinking of the stuff you paint on from the DIY store, not hiring in a "professional" to wave a spray wand around.

Is air-dried oak likely to be resistant to attack, and only the softwood boards needing it, or should I just leave well alone?

Thanks is advance for help - this is a fab site. WIll post a few pics of my project soon.

Robin

 

[biffvernon]

Oak heartwood is very resistant to woodworm. Keep your house dry and you shouldn't have any trouble. Certainly don't do anything now, but look at the timber in May and June when the beetles, if there are any, will emerge leaving their tell-tale piles of pale coloured chewed up wood, called frass.

Paint on treatments don't soak into oak very effectively so are not much use anyway. The key thing is keeping the moisture level low.

 

[FamilyWiggs]

Thanks Biff - I guess I'll leave well alone. What about the softwood floorboards though - don't they have a higher moisture content now?

They will be fairly (very) inaccessible in 5 months time...

 

[Matt Green]

Depends entirely upon the quality of the softwood boards. If they are good quality and are predominantly heartwood- no need for treatment. If they are very cheap and are mostly sapwood, then yes, if they are over bare earth then applying some form of preservative might prolong their life.

If you haven't already got them, buy good quality softwood boards.


Matt

 

[biffvernon]

I guess it can be hard to know what is good and what poor quality. The family Wiggs probably haven't been lucky enough to find some cheap slow grown redwoods, Scott's Pine or even pitch pine. If you ask for flooring grade softwood, what do you get these days?

 

[FamilyWiggs]

The boards are (shock horror) from B&Q - only place I could get the required wide width at a weekend.

They're redwood, and about 11 quid for a 3.6m length. To judge from the cupping/shrinkage already (and the end-grain) they're tangentially sawn and do contain heartwood.

They're nothing more special than that though. So I guess a liberal dosing of worm preservative is in order?

Robin

 

[biffvernon]

No, I wouldn't. The fact they are redwood is more important than that they came from B&Q. You are putting them in a dry house not a garden shed and the cupping/shrinkage confirms the lower humidity in your house than at the store. Woodworm will only survive such conditions in particularly tasty timber.

 

[MdB]

Does Douglas Fir count as a better than pine? I need some additional floor joists to strengthen our old floor and was thinking of paying the extra 20% for Douglas Fir rather than normal pine at our local saw mill.

 

[biffvernon]

Both larch and Douglas fir are what they call 'moderately resistant'. The heartwood is much more rot-proof than the sapwood.

 

[MdB]

Thanks