Raised bed design

lafamillecarrington

Hi, I have just built two new raised beds, and am renovating my four old ones. I wondered about lining them with plastic sheet to keep the soil off the wood, but have found conflicting advice online: some say that it retains moisture in the wood and causes it to rot faster, others recommend it. Does anyone have any evidence for either?

Fairygirl

I've always lined mine. Wouldn't last as long if they were unlined, and moisture will be taken up far too easily by the wood otherwise, at the expense of the plants. 
If they're well lined, any moisture getting into the wood [mostly from rainfall] will naturally evaporate outwards, so I can't see how it can be 'retained' in it.
If the wood is good quality, and also has a decent preservative applied, especially where it's in contact with the ground, it'll last for years and years 

nick615

lafamillecarrington  If you feel that RB's are what you want, could I recommend 6ft x 1ft concrete boards, held in place by angle iron.  No lining required etc.  I used in two's in pic

lafamillecarrington

Fairygirl: I had pretty much decided to line them - the wood is pressure treated and I have given them an additional coat of preservative. Hopefully they will last 10 years.
nick615: Thanks for the suggestion - unfortunately the beds are already made!

Whiterot

You need to line the sleepers  on both the side and the bottom. I use supermarket banners and the raised beds last at least 10 years. I treat them twice a year with clear  decking oil.