Food safe sleeper beds

[livpoksoc]

I have just cut up some UC4 treated sleepers fo make some raised beds ready to grow veg in. But a friend said that even treated sleepers will rot if soil is left up against them, and he recommended lining them with plastic - but I was wondering if that was a safe material that won't leach bad things into the soil?

In terms of drainage, I was planning on laying a plastic membrane on the dug out ground, them pea gravel on top, then placing the sleepers on that, potentially just wrapping the inner walls and feet with something to protect them, but can't find any clear guidance on a safe material to use

 

[Poacher]

Butyl pond liner?

 

[Pat "5mph"]

Ime, eventually all wood rots, actually, it becomes compost, so all good.
No worries, it takes years, I have a planter made of pallets that still stands strong after 10 years, not rotted yet.
Every time I have used plastic in the garden I came to regret it, eventually it shreds, rips, bits of plastic allover the place.
Weeds grow through the plastic, their roots become embedded, hard to remove, shredding the plastic while one tries to remove the weeds.