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Landscape Gardening

Subbase for paving

Hi I'm replacing my paving slabs in back garden and I've already started to dig down to a level and found it already had a harcore type base. Will it be ok to just whack sand and cement and lay the flags or would i need to start again. Also my garden is on a slope towards house. Where do I lay my first flag ? Thanx

4 Answers from MyBuilder Landscape Gardeners

Best Answer

Hi Andy,

As long as you have a depth of 75 - 100mm of compacted hard core an old sub-frame would do the same job. If you put a vibrating plate over the top it will compress your existing.

If your garden is on a slope I would advise to level out your patio and incorporate a good drainage system.

laying your first flag is down to preference, as long as your square off your property and at the right heights your good to go!

Hope this guides you!


Answered 6th Dec 2018

Lay slabs falling away from house. I would leave a gravel trap near house maybe 75/100mm allowing for water to escape and no generate damp onto your property. I'd always do 100mm hardcore base with plate compactor run over the top. 50mm of sharp sand and cement


Answered 6th Dec 2018

As long as the sub base is 100mm think once compacted it should be ok to lay on. If it’s contaminated with soil I would advise to start again. There’s a drainage product on the market called an aco drain they are 1m in length 140mm in width and 80mm deep these are designed to go against your house so your patio can slope back towards the drains to avoid water collecting at the edge of patio/turf. I would start against the aco drains with a wet sand and cement mix at a 4x1 ratio


Answered 7th Dec 2018

Hi Andy.
1. If you have a natural fall towards the house you need aco drainage channels
Along the house joining a drain or soak-away.
2. If the old slabs had sunk then there is not enough hardcore down,
Otherwise the base should be fine ( check for any weak areas )
3 if you are thinking of Indian paving make sure you lay on a full mortar bed
To avoid staining
4. I always start a full slab at the drain channel and Try to avoid any cuts,
And work my way out to the exit to prevent waking on it if possible.
All the best. Kev.


Answered 17th Dec 2018

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