Treated or untreated timber for raised beds???

[gardengnome]

Hi,

I’ve cleared a bed and am planning to make a raised bed in it, however I’m after some advice about the correct type of wood to use.
I was thinking of using untreated timber (2” x 10” boards), but have been advised that it will rot quickly.
The thing about treated wood is that I have small children and don’t want anything nasty leaching into our veggies.

It was suggested that I could use treated wood and line it with heavy duty black plastic.

I suppose I could tuck it under the wood and pull it out, away from the bed as much as possible.

Does anyone here have any thoughts/experience on this topic?
Thanks!

[nickdub]

I use things like old pallets for outside woodwork like that, or sometimes old scaffolding planks which are thicker. Anyway I usually give the wood a coat of fence paint (the 5 or 10 L stuff you can buy in places like B&Q, its water based and does help preserve the wood) after I've sawed it to size but before I screw it together. Of course hard wood would be preferable, but that's very rarely available cheaply.

[ameno]

Treated, definitely.
The fungicide it's treated with won't leach (this isn't like the days of creosote) - if it did, it wouldn't be very effective at preserving the wood, as if the fungicide leaches out then there's none left to stop the wood rotting.

Untreated softwood will last you 2 years, tops, before there is fairly significant rot (I used an untreated length of wood as a tree stake once, because it was all I had and I didn't want to buy another one. It rotted off at ground level in less than a year). Hardwood will last longer, quite how long depends on the species, but hardwood is a lot more expensive.

Lining untreated wood with black plastic will extend its life a little, as it will not longer be in contact with the damp soil, but it will still rot fairly quickly.

[Nicos]

I'd go for treated too..well - we have actually - and I'm very cautious about toxic chemicals too.

Lining also gives slugs somewhere to hide....

[burnie]

It irritates me that we only seem to have access to soft wood that has very little working life span, if you can find Larch at a reasonable price it will last for long time. Most of the treatment on pre treated wood is not long lasting either, Cuprinol make a god wood preserver, but it is expensive. I went for railway sleeper sized wood that will rot, but due to it's bulk, it will last a lot longer, mine are now 5 years old and still in very good condition with no additional painting.

[ESBkevin]

Again treated lumber is the way. I built some raised beds with 6"x4" timbers from pallet stillages and At best I've got 4 years out of them. It's a lot of work to obtain the timber, pull all the nails etc and then have to face doing it again so soon.
Also consider the thought that slugs and snails like to hide in the soil beside untreated timber, don't encourage them!

[Stan79]

Whether treated or untreated... i would still line it with plastic. Old compost bags are fine if you're looking to save money. Pond liner is thicker and would last longer and look nicer. Take your pick. Lining the wood will help keep moisture in the soil and help the wood last longer. Win, win.

[MarkPelican]

Why do you need to put boards around the raised bed at all? Just drag the soil towards the middle and make a "mound".

[Johan]

You can use the green treated wood. It wil not damage or poison the crop.
If people say you may not use it, ten they are not allowed to use rubber or plastic sheets or hoses, as they are made from byproducts of oil.