Wood for raised beds

16 Aug 2006
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Newcastle upon Tyne
United Kingdom
Hi all,

I am planning on building a raised bed for the purpose of growing vegetables however I am a little unsure as to what type of wood would be best to use for the construction.

I have searched the forum and notice several posts suggesting treated timber to protect against rotting. However I was under the impression that most "tanalised timber" or "pressure treated" timber use mixtures of copper, chrome and arsenic in their preservation thereby making them a bad choice for food crops.

To the same end if I use untreated timber and add a preservative to the exterior face there is the potential for leaching and run-off of the chemicals into the crop.

What are most people using?

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Tanalised is best for longevity. Personally I line the inside with wove membrane to prevent soil getting between the timbers as they expand and contract. Just a personal thing.
I used concrete Gravel Boards with impressed random stone wall pattern. Look good and last forever. Old Railway Sleepers do the job also but are expensive.
Some sites suggesting stapling plastic on the inside if you've treated wood.

I've just used fence paint to treat mine.
It is a concern, but will it be a problem unless you've got plants with roots right up against the edges?

Also when it rains, will the water generally be running away from the edges given they're raised?
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Thanks for the replies. Tanilised may be best for the longevity of the wood but im more concerned with my longevity so im leaning towards untreated wood and some low risk stain/preserver applied every so often I think.

While u may be right about the water running off the sides im a bit concerned that once the wood is saturated the tanilised stuff will start leeching chemicals into the soil which over time will build up.

Plastic on the inside is an option but im not totally convinced the arsenic etc will not just partition through the plastic.

May consider stone construction if i can find suitable material.

Time for a trip to the diy warehouse I think!
How long would untreated wood last?

Softwood is fairly cheap so you could just replace it as it rots, obviously the feasibility of this approach is dependant on how long the untreated wood would last.

Does anyone use plastic?
Hi all,

Ok just to update on what I decided in the end.

I found a company called link-a-bord who do a modular plastic system of boards and linking pieces which can be used to create planters, raised beds etc.

Installed a two-tier bed over easter and have it planted up with my veg. 95% recycled plastic, easy and quick to install. Highly recommended.

Just need to stop next doors cats leaving "presents" buried in the soil now and all will be well!

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