Base for sandstone patio - Drainage and support

[StillLearning]

Hi there, I need some advice ...
I want to lay a sandstone patio ontop of a slab circle surrounded by gravel
1
Can I lay sandstone paving directly onto old paving circle which is in great condition? Could I just use mortar directly onto the existing slabs. If so , does it have to be 50mm, or would 25-35mm work as I have to bear dpc levels in mind.The old patio has an incline so I presume drainage would be ok ?
2
Can I use the old gravel as a base for some of the patio? If so, should I compact 14mm to dust into it before laying mortar bed? Or compact sharp sand into it, or neither?
Thanks in advance

[sy76uk]

Don't cut corners.
Get rid of the existing patio.
Dig 140mm plus the depth of the slab below your intended finish level.
Use 100mm compacted type 1 sub base and 40mm of sharp sand mortar for bedding.
Ensure you have a fall away from the building or have a drain in place if the fall is towards the house and lay to taught lines to ensure levels are correct.

[StillLearning]

Thanks . . and get rid of the gravel aswell then I suppose ? Will it not make an adequate base ?

[StillLearning]

Just found on this site saying 25mm mortar is ok for a garden patio and sub bases can be concrete . Since slabs are concrete, why cant they be laid ontop of directly? Doesnt make sense . Also, MOT 1 is crushed stone, so why wouldnt gravel work as a replacemnt if well compacted ?

[DempseyLiverpool]

1. No

2. No

[DempseyLiverpool]

Your asking professional tradesman if it's ok to to do a complete botch up job. Natural stone paving is laid to last a lifetime. Read the site and do it right.

[StillLearning]

Anyone else there prefer to advertise than give informative answers?:p

[sy76uk]

It would take us far too long to explain exactly why you shouldn't lay new paving over old or lay over gravel and even if I tried you'd still have questions.
All the information you need is on the main site.
Your not doing yourself any favours with your last post.
Listen or end up wishing you did.
Your choice.

[StillLearning]

Here s the real answer for anyone else who needs to know the ins and outs : http://www.pavingexpert.com/faq_layover01.htm

[sy76uk]

Do you think we haven't seen that page or know all of the information on it already?
Do you expect us to go into that much detail everytime a complete novice asks a question?
Now you have the information you need you can attempt to lay your patio.
Good luck getting any tips whilst your doing it.

[StillLearning]

Yep as I said, it says 25mm + , and it implies that a solid patio is fine as a foundation so long as it isnt cracked and subsided. I have provided the link for the novices as Im sure they will appreciate fuller explanation

[sy76uk]

Good luck

[lemoncurd1702]

Yep as I said, it says 25mm + , and it implies that a solid patio is fine as a foundation so long as it isnt cracked and subsided. I have provided the link for the novices as Im sure they will appreciate fuller explanation

The page is not advocating that you build on the existing, it's just info for if you insist.
25mm of bedding is pretty much borderline and you may find it difficult to bed the slabs. Personally I wouldn't go below 40mm except for on steps.

[seanandruby]

Every now and again this site gets a diyer who thinks he knows more than the pros', aka arsehole. One of the main reasons we the "experienced guys" don't lay over the top of small element paving is because we don't know what lies beneath it, sub base, or dodgy ground.. We don't know if the existing will take the extra weight, or will the lot subside and start failing. Also height can be another reason because of breaching the dpm. Best to take it up and prove the sub base is sound. We use Sub base mot because building regs dictate that we use it if needed. Stones, gravels etc; are for dressing, or can be used on drives and paths. You could mix the gravel with sand and cement of you so wish.
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