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Topsoil Requirements


So this is my garden layout - its changed a bit since then, added beds around the side and put some decking at the front instead of half dead grass.

Now the question is about soil amounts. I made a bit of a gaffe when I first did it as I worked out that those 4'x8' beds needed a tonne of soil apiece ... Now you see why I'm asking you for help - oddly enough 1.5 tonnes did the lot, so ended up with a lot of spare, thankfully after installing raised beds round the edges and with shrinkage i managed to use all 3 tonnes. 

Now those little cut off corners have been turned into beds and I'm scared of my own maths ... ive worked out that 4'x4' at a depth of 12 inches would be 16 cubic feet so x2 beds would be 32 cubic feet (0.9 cubic metres?) - but again that maths tells me I need another tonne bag as the place I buy from estimated their tonne bag at 0.73m3 which having bought their bags before did not add up.

Ive already done this maths wrong as 2 lots of 4x4 is the same as the original 8x4 - so how much do i really need?!



  • raisingirlraisingirl Posts: 6,651

    Your maths for the new beds makes sense. But it doesn't tally with what you've already done. Are you sure it's a foot deep - are you maybe only part filling them?

    Last edited: 08 June 2017 16:44:26

    “Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first” 
  • TopbirdTopbird Posts: 7,891

    4' = 1.2m

    12" = 0.3m

    So 1.2 x 1.2 x 0.3 = 0.432 cubic metres per bed

    So 2 beds = 0.864 cubic metres

    Which is roughly what you've calculated. Gold star for mathsimageimageimage

    I've found that a tonne of soil can be nearer to 1 cubic metre depending on moisture content .

    If you can use surplus soil around the garden or store it for future use I'd buy another tonne in and use any surplus elsewhere.

    If all your beds are now full to capacity I'd be tempted to source the largest prepacked bags of soil etc you can find and just buy what you need.

    That might be more expensive than a bulk buy but you won't have any waste and you can buy a mix of stuff like farmyard manure, John Innes No 3, topsoil - whatever suits the proposed planting.

    Alternatively can you find someone who will deliver a half tonne and then top it up with prepacked material?

    Heaven is ... sitting in the garden with a G&T and a cat while watching the sun go down
  • EnchanticaEnchantica Posts: 37

    Aha, see this is why I can't be trusted to do maths.

    Upon remeasurement - (done so quickly i have squelchy mud between my toes ..) apparently the depth is indeed 9 inches not 12 and i filled them to an inch off the top for easy cut&come again so I should have been doing my maths based on 8 inch depth not 12 so in fact I need 0.5 m3 total.

    Seems you hit the nail on the head raisingirl, again you come to my rescue!

    That still seems like a lot of soil but that could be as i did the lasagne method at first so can probably lop off another inch depending on the thickness of the cardboard.

  • EnchanticaEnchantica Posts: 37

    Might indeed try and source that half-tonne Topbird and as you say, that way I have the room to mix in my own amendments. The stuff i bought originally was a very sandy topsoil mix so hardens quite a lot, lesson learned for next year - more compost! I have the spare builders bags from the 3 tonne being used for partially done compost and grass clipping drying. (useful items!)

  • EnchanticaEnchantica Posts: 37


    Here's an updated pic anyway, bit of a mess and still need to put the trellises up properly but its coming along. Would prefer it much more if I didnt have a huge overhanging tree from the garden behind shadingme out :(

  • TopbirdTopbird Posts: 7,891

    That's coming along really well Enchanticaimage

    I assume the tree belongs to a neighbour? Have you spoken to them about raising the canopy / reshaping it? Perhaps if you offered to help (or even fully) pay for the work.

    We bit the bullet and paid for work to be done on a tree on a neighbour's land. Made a big difference to us - and she would never ever, in a month of Sundays, have paid for it herselfimage 

    Heaven is ... sitting in the garden with a G&T and a cat while watching the sun go down
  • FairygirlFairygirl Posts: 52,110

    Don't worry - the soil level will settle over time anyway.  image

    Most people need to buy more soil/compost etc as the weather settles the ground, because usually not enough is ordered, rather than too much! 

    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • IamweedyIamweedy Posts: 1,364

    Oh dear I was doing those calculations earlier this year. My maths are poor and  dealing with the raised bed linear measures  and getting them into cubic  mtrs  was a nightmare.

      You will probably need more than you think you will. It sinks.   We bought 4 x cu mtrs bags and found someone freecycling soil  locally as they were digging out a garden to make a drive and got several bags more.

    'You must have some bread with it me duck!'

  • EnchanticaEnchantica Posts: 37


    Was looking into the legalities of trees and chopping and apparently as long as you return the wood you can remove overhanging branches, but it's unlikely they will want them back so that's why I do wish to speak to them first. 

    As for settling yes I found that, which was why I was glad of the extra after all. Managed to top them up and still have a bag left over to fill those side beds. Want to fill them with berry bushes - hence the tree concerns at the back. Gets quite dark. 

    Everything took a bit of battering in the wind but no snapped stems.

  • raisingirlraisingirl Posts: 6,651

    It's looking great image. Maybe paint the fence a light colour to make it a little lighter under the tree?

    “Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first” 
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