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stone and sand base for flagstones

Discussion in 'In the Garden' started by DIYalot, 13 Aug 2019.

  1. DIYalot

    DIYalot

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    Hi. I'm laying flags in my front garden adjacent to the house. I've layed down stones (sandstone) that have come up from my garden (I live on stony ground) - for the purpose of a hardcore base. I've got a 8x8 Roughneck tamper and I've managed to compact the stones. Now, this compaction is not to a professional standard, I mean the compaction does not match what would be obtained by a large roller machine. On top of the hardcore I'm laying down a 1 inch layer of sharp sand. At the moment the sand is damp, not dry.

    Q1: So, given that the compaction is not to a professional standard, would it be advisable to lay down a membrane on top of the hardcore and lay the sand upon that?

    Q2: Is it OK to lay the flags on damp sand, or should it be dry?

    Thank you. Rich
     

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  2. footprints

    footprints

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  3. DIYalot

    DIYalot

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    Hi. OK thread moved into "in the Garden". Reason I posted is because I noticed that when some rain landed on an area not covered by some covering I'd laid down to protect the sand laid down, the sand got washed into my base I'd created. Because of course my base has many voids, not been very compacted. So, that raised the issue of whether my base is compacted sufficiently, even though flags will rest atop of everything. I'm assuming that when compaction is done with a heavy roller, there are zero voids on the base, or very small ones. I'm also wondering if the sand out to be dry when I spread it out on the base I've made.
     
  4. geraldthehamster

    geraldthehamster

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  5. DIYalot

    DIYalot

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    Reading the stuff on the pavingexpertdotcom website, given that my hardcore is not so well consolidated, which poses a risk that sand will fall into voids over time, I think "footprints" is spot on by advising the flags be laid on a sand/cement mix. In the words of the paving expert the bed or laying course ought to be (in my case) "hydraulically bound". What I don't want though is to have a cement mix adhering to the flags. And so I'm likely to place a PVC membrane on top of the bedding layer, so flags will not stick to it.
     
  6. Charlie George

    Charlie George

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    You can't lay flags like that, most people want flags to adhere to bedding material,is there a reason for wanting it done this way.
     
  7. geraldthehamster

    geraldthehamster

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    Having the mortar bed adhering to the flags is exactly what you do want. It's what's meant by bedding flags.
     
  8. DIYalot

    DIYalot

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    In my case the flags are councill flags, i.e. 900mm x 600mm. They wiill be a restraining border around the flagged area, consisting of the front wall of the house on one side and on the three other sides a border consisting of modified flags (300mm x 900mm) laid in sideways. So, these flags are not going anywhere when laid. Which will I think allow me to prevent the flags adhering to the bedding without negative consequences. Anyhow, I prefer that the cement bedding does not adhere to the flags. I'm thinking about laying down a PVC membrane unless there is a product that I can spray onto the flags. Or maybe I could paint the flags with a paint that adheres to concrete, but when dry won't adhere to the concrete bedding. Such as paint for concrete floors.
     
    Last edited: 20 Aug 2019
  9. geraldthehamster

    geraldthehamster

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    Up to you, but that is not the way to lay flags. There's no point in using a mortar bed at all, if it's not going to do its job.
     
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  10. scbk

    scbk

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    I would try and fill in the voids in the stones with sharp sand/quarry fines/scalpings/whatever you have to hand, then compact it again, it might need a sprinkle of water.

    "council slabs" are fine on a layer of sharp sand IMO
     
  11. geraldthehamster

    geraldthehamster

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    Either sharp sand, if the sub-base is well-compacted, or mortar. Either way, a PVC sheet is not part of the equation.

    Best way if not sure what you're doing is to pick one of the methods on the Paving Expert site, and follow it.
     
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