Timber and treated timber: what goes into treatment?

[ToughButterCup]

Reading through all the guff about timber - my God there's loads about it - I am still not sure what the difference is between treated and untreated timber.

 

Is it possible to ' ... treat ... ' timber yourself?

 

[Onoff]

Reckon you'll have trouble pressure treating timber yourself as much of it is done this way.

 

Bromide treatment (by brush) is pretty good (enviro friendly?) as long as it won't get wet. 

 

Can't see what's wrong with Creosote mixed 50:50 with old engine oil... 

 

[ToughButterCup]

I'm inherently suspicious of  treatments. 

It's a bit like a hairdresser asking me if I want any product  on my hair. 

It's quite fun watching a hairdresser trying to explain what product  is. Similarly,  nobody down my woodyard knows what treatment  is.

Yet you can buy any amount of wood treatment  online or from any of the sheds. Bet snake oil works better than anything.

[Jeremy Harris]

When we lived in Scotland there was a local sawmill that had their own timber treatment chamber (this was back in the bad old days of CCA, which in reality turned out to be not as toxic as some thought, but that didn't stop the EU clamping down on it's use).  They were really helpful people, and being curious by nature I asked them loads of questions whenever I was over there picking up timber. 

 

From what I could gather, the process was quite involved.  First they had to kiln dry the timber to a really low moisture contact, then they loaded the timber into a pressure chamber, that looked like a massive tubular boiler.  This was then sealed up, the air pumped out and the CCA solution allowed in and pumped up to a high pressure.  IIRC, there was a rule of thumb they used for penetration depth with time, the longer the timber stayed in the chamber the deeper the preservative penetrated.  This was reflected in the price, large diameter fence posts were more expensive than rails or boards, because they took a lot longer to treat.

 

Nothing you can paint or spray on will penetrate very deeply; a mm or two at most.  You can set up a dip tank if you have the patience.  This is how telephone and power poles were conventionally treated.  They were just left for months in large pits filled with creosote, which penetrated very deeply into the timber and worked as a very effective preservative.  Despite its smell, I still think there's little to beat creosote soaked well into nice, dry, timber.

[Onoff]

I've half filled a bucket with Creosote / other wood treatment like 5 Star Cuprinol then stood on end dry 100mm fence posts in the bucket. Left for a while and the stuff has "crept" a good few inches up the dry wood above the level of the liquid. I wonder if it's actually going up the natural fibres of the wood to the full depth of the timber?

[DavidFrancis]

I think I've seen some sizes of treated timber in the sheds.  And Berry's will pressure treat any of their timber for you for an extra charge.  I haven't got an up-to-date price sheet for sawn timber, but (for example) 50x150 planed timber costs 38p/metre extra for pressure treated - and it come in clear, brown or green!  I think they only do two treating runs a week so I've sometimes had to wait for three or four days before I could pick it up.

 

And I agree with Jeremy that painting or spraying's not going to be as effective.  I ofter soak cut-ends in a tray of wood preserver for a minute or two and, as @Onoffsays, it soaks up quite a way.

[Gone West]

12 hours ago, recoveringacademic said:

Reading through all the guff about timber - my God there's loads about it - I am still not sure what the difference is between treated and untreated timber.

 

Is it possible to ' ... treat ... ' timber yourself?

 

It depends on what you want to use the timber for. There are lots of different treatments. For my fence I used Creoseal and my local timber yard use Protim for above ground timber, which is what the BCO wanted.

http://www.kopperspc.eu/products/protim.html

[DavidFrancis]

Berry's use one of the Koppers treatments, but its NatureWood.

[joe90]

I used to spray creosote onto our hen houses etc when I had a small holding in Shropshire, I did have old Fireman’s breathing kit (dont ask). To stop me breathing the fumes, I also recon it stopped mites etc from breading . The good thing about spraying was you could hover over really dry bits till it stopped sucking it up, I bet they will last forever!. Note, I don’t recommend spraying creosote for health and safety reasons ?.

[Ferdinand]

Previous comments about have it. I have treated timber by dipping and painting and standing it in buckets. If it is fenceposts then consider PostSaver.

 

It will perhaps surprise how much liquid is absorbed.

 

F

[joe90]

I have found that fence posts rot at ground level where they are wet then dry, if permenantly wet they seem ok. I had an old barn where the tree trunk posts in the ground (very wet) and above ground we’re fine but at ground level they had rotted to nothing.

[Jeremy Harris]

9 minutes ago, joe90 said:

I have found that fence posts rot at ground level where they are wet then dry, if permenantly wet they seem ok. I had an old barn where the tree trunk posts in the ground (very wet) and above ground we’re fine but at ground level they had rotted to nothing.

 

 

Me too, and I think that's where the post savers come in.  If you happen to have some left over flashband and primer, then I reckon that will work as well as a post saver, for a bit more hassle.  I have two left over rolls of flashband and a tin of primer that I decided not to use, and plan on priming our next batch of fence posts around the ground level area, then wrapping them with flashband, then giving them a run over with the hot air gun to melt the bitumen on the flashband.  I shall report back on how well it works.  No cost saving over postsavers I suspect, but in my case it will get rid of a couple of rolls of left over flashband.

[DavidFrancis]

For a definitive guide you could buy one of these from TRADA (Timber Research and Development Assn)

https://www.trada.co.uk/search?term=treatment&IsSearchPage=true

[Onoff]

Seem to remember one Tomorrow's World years back where they were up in Scotland following a utilities company who were going around drilling and fitting CO2 powered wood preservative "injectors" to the base of their poles. 

[Ian]

@recoveringacademic

The relevant British Standard is BS 8417:2011+A1:2014 Preservation of Wood.

It takes a risk based approach.

Quote:

"To determine whether a timber component needs preservative treatment, the following should be assessed:

• the biological hazard indicated by the use class;

• the likelihood and consequence of failure;

• the inherent natural durability of the wood to be used"

 

The standard then looks at the different service situations where wood is used based on 5 "use classes" with 1 being the least risky and 5 being the most risky.

The example given for use class 1 is "All timber in normal pitched roofs except tiling battens and valley gutter members; floor boards, architraves, internal joinery, skirtings; all timbers in upper floors not built into solid external walls"

The example given for use class 5 is "Marine piling, piers and jetties, dock gates, sea defences and ships hulls"

 

In the risk based approach that the standard takes these use classes are then assessed against a set of service factors based on risk of failure where factor A is a negligible risk if the timber fails and therefore preservative treatment is not necessary to factor D where failure of the wood would result in injury or death. and therefore treatment is essential. Desired service life is also considered.

 

The table attached below is just one example from BS8417 - there's other tables for the various types of timber treatment. Let me know if you need to know the preservation recommendation for any specific situation in your build.

 

Ian

 

 

Edited July 10, 2018 by Ian