[Closed] Retaining soil behind sleepers , do i need a plastic liner of some sort ?

I'd probably go for some gravel back fill and some drain holes down the bottom as when I've used plastic behind even treated wood you just get lots of mould growth. At least with the gravel then water would circulate. that's just me though from previous experience with tannelised timber raised beds.

If you are holding back a veg patch then I wouldn't use sleepers though due to the chemicals.

As above, do not use sleepers for veg due to treatment with creosote- nasty stuff.

The reason that sleepers were treated with creosote/ tar was to help preserve them. TBH, I'd not bother with any kind of liner/ membrane at all. I'd want the soil behind to drain as freely as possible, not waterlog and thus press hard upon the wall.

What about using gabions instead?
Dead easy install, and it's solid.

If you're buying "new" sleepers then they'll probably have been treated with a safer "eco" preservative. Reclaimed used ex-railway sleepers will have been creosoted which, as others have said, is not good (from a H+S perspective).

I built a 1 metre retaining wall from softwood sleepers, the ground was cut back behind the wall with a weed membrane type fabric against the soil/chalk, and then the gap filled with gravel.

The wall gets wet from the front but we get no seepage from behind so it seems the gravel is doing its job and the wall isn't permanently wet.

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My original plan was gabions but in the 1st photo, that heap of soil on the left was was all hand dug, and there is even more chalk on the right that was compacted into a raised patio. I probably dug an extra 0.3m into the garden to make space for the wall, gabions would have been just over 1 metre plus buying in stone to face them (I had plenty of concrete I could have used to at the back)