Tanalised Timber Issues?

swain90 · 24 May 2017 at 08:39

Hi,

I'm just in the process measuring up for a garden planter.

I was going to go with some tanalised timber as I understand that it's treated to protect against the elements...however, I stumbled across this article;
https://groups.google.com/forum/#!topic/uk.rec.gardening/sexa7FIsOs4

It explains a little how the chemicals used to tread the wood can seep into the soil. As this is going to be used for some vegetables I'm not sure what type of timber I should be using.

If anyone has any input that'd be useful!

Cheers,

Swain90

PlacidCasual · 24 May 2017 at 08:58

As it says in that link Tanalising is a trade name for a process. In the 60's and 70's tantalised wood would contain arsenic I'm fairly confident that modern treated wood does not, which is why it is so ineffective. I've seen tantalised wood from the 70's that has permanently been in a wet/dry interface and is still standing. I've seen modern tantalised wood rotten through in 5 years. Personally I wouldn't worry and haven't although that is not scientific evidence.
If it's for a raised bed you could easily line the inner surface with a plastic sheeting to cut down the risk of rot transferring into the soil. Personally I did this on some polytunnel raised beds to reduce the rot rate.

swain90 · 24 May 2017 at 09:01

Thanks for the reply.

Like you said, lining will probably be the easiest so I'll get some clear membrane stuff to line it with.

wilber · 24 May 2017 at 09:04

As above modern Tanalised timber is crap. Fencing stakes and post of this variety are snapping off after 5 years. We will now only use "fence and forget" which is a creosote treated timber. If you want it to last use old railway sleepers and line it.

swain90 · 24 May 2017 at 09:13

@wilber from reading online, old railway sleepers are awful for gardens as all the grease and soil seeps out and pretty much kills the soil.

Amp34 · 24 May 2017 at 17:53

I put in some raised veg beds recently and just decided to go for untreated wood. Yes it will rot but you'll still get 5 years out of it anyway, just stick with heavier stuff - either sleepers or 6x2 or similar, rather than thin stuff.

andicole0 · 24 May 2017 at 18:13

wilber said:
As above modern Tanalised timber is crap. Fencing stakes and post of this variety are snapping off after 5 years. We will now only use "fence and forget" which is a creosote treated timber. If you want it to last use old railway sleepers and line it.

Real creosote is not available to the general public, what is "creocote" like as an alternative?
Andi.

thezappa · 24 May 2017 at 18:45

andicole0 said:
Real creosote is not available to the general public, what is "creocote" like as an alternative?
Andi.

Yup. Saw it Wickes once and wondered why they had spelt it differently.
From wood-finishes-direct:

Barrettine Creocote Is a bitumen/wax based treatment that has similar physical, water repellency and application characteristics to the traditional Creosote fence paint, but contains no biocide / preserver.

Please note: This product is not suitable for decking or exterior wooden furniture.

@OP if you want to use non-treated wood, you could if you have a big enough bank balance use a tropical hardwood like greenhart, absolutely no way that will rot, at least not in any of our lifetimes.

drunkenmaster · 25 May 2017 at 01:31

Could once a year before planting new stuff take out the soil, remove liner, give it a wash with a stiff brush, clean it as good as possible then give it a few coats of teak oil before putting everything back. Could help it last longer.

Most treated wood should be pretty safe these days with only copper based rot protection used which won't be particularly bad though maybe less effective.

Hard to compare to much older wood with different treatments because wood is probably changing, the types commonly used and how quickly it's grown has probably changed. Could be wood from 30 years ago was just older better grown wood that was stronger, denser and more water resistant and less that the treatments got worse while getting safer. Could be a mix of both.

wilber · 25 May 2017 at 09:12

swain90 said:
@wilber from reading online, old railway sleepers are awful for gardens as all the grease and soil seeps out and pretty much kills the soil.

Old sleepers should be fine with a lining (as its soaked in over years). You could pressure wash them off to get any excess away too. I coat rails and posts with it yearly, the grass burns off where its spilt but give it a month and its growing back.

andicole0 said:
Real creosote is not available to the general public, what is "creocote" like as an alternative?
Andi.

Thats true hense why i suggested buying second hand pre treated timber. Ideally posts need boiling in creosote to get it to penetrate deep enough. Creocote is poor imo but i want my timber to last decades rather than a few years.

drunkenmaster said:
Hard to compare to much older wood with different treatments because wood is probably changing, the types commonly used and how quickly it's grown has probably changed. Could be wood from 30 years ago was just older better grown wood that was stronger, denser and more water resistant and less that the treatments got worse while getting safer. Could be a mix of both.

You're correct on both counts. Today we tend to use fast growing species in the UK which are less dense, wood treatments are poorer also.

Mark A · 25 May 2017 at 11:14

wilber said:
You're correct on both counts. Today we tend to use fast growing species in the UK which are less dense, wood treatments are poorer also.

If you go to a decking/fencing specialist they are likely to stock redwood external timber that has been pressure treated properly and it will last a lot longer than the cheaper spruce they use in DIY sheds. When you make a cut in this you can see the green treatment has penetrated a good 5-10mm, but the timber from DIY places there is hardly any penetration. You can usually tell if its spruce or redwood by the weight and how dense the grain is.