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Building a raised bed

ysemayysemay Posts: 2
in Tools and techniques
Looking for some advice on building a couple of raised beds. 

They will be in a small city garden so will have to back onto brick walls (not house walls). I am planning to use this wood as our budget is a little limited but am worried they are not thick enough as have seen a lot of recommendations of 3cm + 

https://www.travisperkins.co.uk/gravel-boards/gravel-board-treated-green-22mm-x-150mm-x-3000mm/p/917538

As they are built against a brick wall I am wondering whether it would be sensible to line the brick with some kind of waterproof membrane - there isn't any space to build 4 sided beds but want to make sure the wall is protected as much as possible. 

Also do people recommend treating the wood with anything additional? I am considering using some kind of fencing paint but not sure if that is advisable for use next to plants?

Thanks!

Posts

  • BobTheGardenerBobTheGardener Posts: 11,391
    Yes, line the wall with DPC membrane.  You'll also need to line the wooden sides with the same or similar waterproof material as even treated gravel boards will rot in just a year or two if in contact with wet soil.  I would recommend using thicker timber, such as decking boards, scaffolding boards or sleepers, iif you can.
    A trowel in the hand is worth a thousand lost under a bush.
  • AlbeAlbe Posts: 123
    I built raised beds 7yr ago with treated wood, without any membrane, the wood is rotting but still okish.
    For my more recent beds I used Noppenfolien.
  • nick615nick615 Posts: 1,292
    ysemay  Timber of the wrong sort can be false economy, through needing to be renewed every 'x' years.  Concrete 'boards' will last pretty much for ever.
  • koyukanokoyukano Posts: 72
    I think that would be fine ysemay for a one tier raised bed (only 1 gravel board high), obviously if you are building the raised beds up to 4-5 gravel boards higher then the higher you go the more outwards presssure will be exerted on the lower gravel boards and the thicker they will need to be. 
  • AlbeAlbe Posts: 123
    My fav are those I used for my last beds, impregnated timber deck boards, 2cm thickness. With very thick (expensive) inner plastic sheet to keep off the humidity. Beds heights 50cm, otherwise 1m x 1m or 0.5m x 2m. Outwards pressure is ok.
  • WildFlower_UKWildFlower_UK Posts: 218
    I asked a not dissimilar question on this forum a few weeks ago - you might find some of the comments and suggestions helpful  :)

    https://forum.gardenersworld.com/discussion/1048002/off-the-peg-raised-bed-recommendations/p1 

    My initial query was about off the peg raised bed kits but there's lots of useful advice about how to make them from scratch, which I'll be doing now too. Basically line the inside where any soil meets either your wall or the wooden boards (I'm doing this with old compost bags I saved up) and you should be fine. If the wood is already treated it would probably last a good time, although I'll be staining mine as the second-hand scaffold boards I'm using need a little spruce up!

    Best of luck, and happy growing!
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