Raised flower bed and borders - line with DPM?

[Zetec-S]

Currently in the middle of a garden revamp, and ripping out some old raised beds I've found the sleepers are very rotten on the raised side. They've been in about 6 years and weren't given any additional treatment and had no lining inside. As part of the revamp we'll be putting in some replacement sleepers to form a couple of raised beds (about 8" x 4" x 2" high), plus a lower run to separate the ground level borders from the grass.

Would it be better to use some sort of plastic/damp proof membrane underneath and up the inside of the sleepers to try to prevent the damp soil getting in contact with the wood, to try and extend its life? Or is that going to just "sweat" anyway and make little difference? Obviously I wouldn't line the whole of the inside of the raised bed, so water could still drain down into the ground.

Just curious if anyone has any experience of doing this and whether it is worth the extra effort/expense?

[r44flyer]

I wouldn't bother. Lining might help a little but I just accept that wood buried in soil is going to rot. Use pressure treated timber sleepers and put them on bricks in the corners so they have good drainage.

[Bluevanman]

Years ago I made a planter from an old pallet and did exactly what you're suggesting.I lined the sides with plastic sheeting.Still going strong

[SunsetZed]

I lined mine (made out of pallets) using the bags that the compost came in and will see how it holds up.

I figured there was no expense and little effort involved so why not.

[Randy Winkman]

I would definitely line the insides. And that not a lazy/non-gardeners option. I've seen it done on a TV gardening show too. You can just do it with old compost bags.

[pdstm]

What I've seen done before is painting the inside using Bitumen Paint, not done it myself so can't give any first hand experience.

[Frankychops]

Get some azobe sleepers, they won’t rot. Or get Oak.

[brycheiniog1]

I built mine out of azoba sleepers (get good at sharpening chainsaw chains!) and lined the inside with cavity drain tanking membrane. We will see in a decade or two how well it has worked!

[21TonyK]

I lined mine with weed membrane purely because I had lots kicking about. 8 years on they are still doing what they should.

[Frankychops]

brycheiniog1 said:

I built mine out of azoba sleepers (get good at sharpening chainsaw chains!) and lined the inside with cavity drain tanking membrane. We will see in a decade or two how well it has worked!

I’ve retaining walls in Azobe. British waterways use them underwater, I think they’ll outlast my time on this planet.

[OutInTheShed]

Frankychops said:

I’ve retaining walls in Azobe. British waterways use them underwater, I think they’ll outlast my time on this planet.

Wood sometimes lasts better underwater than being exposed to damp and air.

I built some planters and lined them with thick black polythene.
The point is not only to keep the water in the soil away from the wood, and to reduce drying of the soil, but also to keep the biocides on the timber out of the soil.