I'm trying to avoid using toxic timber preservative while building a timber frame house. What do I need to look for in the studwork timber? A lot of the structural C16/24 timber I am looking at is pressure treated - is that the same as the toxic preservatives and, if so, is it possible to get untreated? Is there anywhere that I will have to use treated?

Thanks,
Debbie

I get the impression that all the old nasty pressure treatments have gone. This from 2007...

http://lancaster.unl.edu/hort/articles/2007/pressurelumber.shtml

By now, the pressure treated lumber you will find in stores has been treated with one of the new, more "environmentally friendly" pressure treatment chemicals. The former, long-used treatment known most commonly as CCA has been out of use for over two year, so stocks of lumber using that treatment process should be gone.

Today's pressure treating chemicals rely on copper in new formulations to stabilize it in ground contact and wet conditions. You will see codes such as ACQ-C, ACQ-D, and ACQ-D Carbonate on some lumbers. These are all versions of Alkaline Copper Quaternary. Other pieces of lumber will bear codes like CBA-A or CA-B which indicate they were treated with a Copper Azole-based material. Copper is the primary decay-preventing chemical in all of these treatments.

Note if you do use ACQ treated timber, you HAVE to use the correct fasteners - regular nails and screws must not be used as they will possibly corrode. ACQ timber here is only used for outside purposes (such as decks and patios) and you have to use double-thick coated galvanized fasteners on it. You can't use regular nails as far as I understand. Also, ACQ timber here shrinks a lot usually - our stick building untreated timber is all kiln dried to the right moisture content (or is supposed to be) so it doesn't shrink and twist.

Paul in Montreal.

No none, woodworm cannot digest dry wood -- they will only go for it if it high moisture content not found in properly built homes, they do also like glues and lacquers which is why some furniture and plywoods get so badly damaged.

In roofs I have only ever commonly seen them in the ridge boards and in houses in damp floors or under WC/ bath or areas of repeated roof leaks.

My new build timber frame is made solely of Steico I-beams but I don't know if they are treated or not. The outside cladding is untreated cedar as are the fascias and the soffits are untreated marine ply. The battening for the cedar is treated as required by Building Control. I used stainless steel fixings as required for fixing cedar.

I think uk regs. Say needs to be treated to protect from insect attack if you're in a specific area. Eg. Longhorn beetle in Bracknell area berkshire etc.
I struggle to find untreated nowadays. Just seen as upselling by merchants. Easy way to increase profitability of selling a piece of wood.
Having said that. If treating has the effect or potential to increase useful life span of a building or product then negative may be irrelevant.

It must be a regional thing. I have no problem at all (in Sheffield, S. Yorks) getting untreated c16/c24. We did an extension last year and BCO was entirely happy with untreated. We did not, though, need a guarantee 'badge' or a mortgage.

Posted By: Jonti

Posted By: Beau

Posted By: tonyNo none, woodworm cannot digest dry wood -- they will only go for it if it high moisture content not found in properly built homes

Are you sure about that? I have often had to repair furniture with woodworm from perfectly dry homes.

Tony already covered that Beau

Posted By: tonythey do also like glues and lacquers which is why some furniture and plywoods get so badly damaged.

Yes I see that but I have seen worm in furniture with no evidence of being wet and not attacked on glue or lacquer. A classic place is draw bottoms which are unlikely to get wet and normally just slide in so no glue and almost never have any finnish.

Ed, this was a reply from Timber to a similar question I asked a while ago.

"Essentially marine plywood is the same as a softwood ply with an exterior quality glue line. Hardwood marine plywood only differs from softwood ply in the material used for the veneers. Marine ply needs to use timber which is moderately durable. The glue lines are exactly the same between marine and softwood ply with an EN636 class 3 glue bond."

Boron can be splashed around the structural timbers after fabrication, protects against woodworm but not rot, is non toxic, is leached away by water flow.

WBP plywood doesn't exist any more. The standards for WBP ply were withdrawn about 20 years ago!

The current grade of external plywood is EN636-3.

As for timber treatment, it is not essential with timber frame buildings, but warranty providers spec it for 'added assurance'. So if you want an NHBC or Prem/LABC warranty, you will need to use treated timber or see if they will 'let you off'.

No technical reason to use treated timber, a well designed and constructed timber frame building won't need the timber to be treated to achieve good durability - design is key. Wet treated timber will decay in the end anyway, the treatment just slows down the inevitable. Using a treated sole plate is a good idea though, just in case.

I have found a tin of Tanalized treatment in my shed which names the harmful ingredients. I am no chemist but it would be interesting to hear what the dangers of the ingredients are.

CopperCarbonate hydroxide 2.25% w/w
Boric Acid 0.494% w/w
Propiconazole 0.05%w/w