Define Hardcore?


Postby elduderino » Wed Apr 18, 2007 8:55 am

Hello,

I'm laying a small patio area at the back of the garden ~3.5m by 2.5m.

I've read numerous projects, guides but would like to try and get some clarification on the whole hardcore, sub-base issue.

I'm currently preposing the following layers:
1) Weed Fabric
2) Broken pieces of old patio slabs various sizes but not crushed, filled in with a sand ballast and then levelled by treading on wood board. Overall depth of both making ~6/7cm
3) Then a fairly dry layer of sharp sand / cement mix at a 6 - 1 ratio
4) New Patio Blocks 38mm
5) Pointed with patio grout or similar.

I'd love a confirmation that I have a reasonable plan. My main concern is if using broken slabs as hardcore will suffice. If not where do I buy hardcore? In what form's can it be purchased? Do I need to go to extreme lengths of breaking up olds slabs and then firming down with machinary?

Thanks for any guidance,
elduderino
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Joined: Tue Apr 17, 2007 4:07 pm

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Postby thedoctor » Wed Apr 18, 2007 1:23 pm

The hardcore you suggest could be counter productive if you compact it the way you suggest. If its not compacted "to refusal" ie to its fullest extent it could well sink later and even a little subsidence could ruin the effect. See our project on block paving and compact well with a vibrating plate. Failing that, and its often much easier, use scalpings as shown on our garden makeover project. There is no need to put cement with the sand for block paving as shown in the project.
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Postby elduderino » Wed Apr 18, 2007 1:51 pm

Thanks for the advice.
I've read the project but unfortunatley it doesn't tell me what scalpings are? Please can you describe? Likewise with the hardcore, are you saying that I should not old use pieces of slab or that I can but should compact using a vibrating plate? And I guess overall I'm still unclear on where I would purchase hardcore from, what form it comes in etc..?
Thanks sorry if it's basic.
elduderino
Posts: 5
Joined: Tue Apr 17, 2007 4:07 pm


Postby thedoctor » Wed Apr 18, 2007 5:34 pm

Scalpings are simply broken stone, usually broken into pieces about 40mm. They are surrounded by the stone dust and compact very well. They are used in road construction and available from builders merchants. Hardcore is boken brick, slabs, stone etc which is random in size and only beneficial if its compacted well. Because of its randomness its very difficult to get level and make getting an even layer of sand on top of it very difficult. Yes you can use slabs but if you do definately compact with a plate. Hardcore is usually available from demolition sites as demolishers are pleased to get rid of it. Its used a lot under concrete slabs and because of the weight of the concrete will stay stable.
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