What waterproof barrier for raised bed?

Having a google fail at the moment. I’ve got a 200mm high sleeper bed that is 12m long and I’m after something to staple to wooden kickboard of the the fence at the back of the bed to stop the rot, what am I looking for? Ideally it would be a roll of some kind of barrier that is 400 – 500mm wide, what am I looking for?

Thanks!

I’ve used something similar to this as I had some spare from an extension.

https://www.screwfix.com/p/capital-valley-plastics-ltd-damp-proof-membrane-blue-1200ga-15-x-4m/98181

I attached to the sleepers with stainless steel screws and large stainless steel washers, might be overkill but again I had some spare from rat proofing our decking.

Damp Proof Course – comes on a roll in various widths. I’ve just done my raised beds with it using 2X150mm with an inch overlap as it was cheaper than the 300mm.

Thanks both.

@Oggles That’s just the ticket, great.

If you put a waterproof layer in contact with the wood it will just keep it wet, and staple holes will allow water to seep through. I would treat the wood with a penetrating preservative, and put gravel next to it to allow water to drain off it, with damp proof course between the soil and the gravel.

yeah kind of what greybeard is getting at. you won’t stop the rot, but will delay it. i make my raised beds from old pallets (pressure treated) lined with geotextile  (markduk in swedish sorry not sure of english name) and expect them to last 3-5 yeers. i always treat the wood with something too

I use DPC when I’ve built raised beds for customers.

Yep as said layer of stones under wood and up between wood and membrane then soil. Use DPC, see if theres any building sites nearby to scavenge a length from.

Treat the wood first if it’s not already done.