Paving over a concrete sub-base

David 1234 · Post: # 103627Post **David 1234** Thu Apr 30, 2015 11:14 pm

Hello everyone. I have an old driveway comprising of 65mm pavers over approx 30mm sharp sand over a 100mm concrete base. I know that current wisdom and this site don't endorse this method but my driveway dates from the 80s and there are only a couple of very tiny ruts.

I'm going to install a new driveway and hate the idea of ripping up a perfectly good concrete sub-base. If I use the vertical core method of drainage detailed on this site as a precaution, is there any reason why I can't crack on.

I know that Mr Lager Lout has mentioned before an old time landscaper using this method with no ill effect.

Thanks for any comments or help in advance.

mickg · Post: # 103630Post **mickg** Fri May 01, 2015 12:28 am

that's the best way to core drill the existing concrete to give drainage to the sand laying course

David 1234 · Post: # 103634Post **David 1234** Fri May 01, 2015 8:36 am

Thanks Mick. I had toyed with the idea of a rigid driveway, utilising the skills of a bricklayer pal of mine. But I've read so much negative about rigid construction on this site so am nervous, not least with the fact that I've got no movement joints on the existing concrete pad. Mick why is it so problematic - any reason why you can't lay ordinary pavers in the same way you'd lay setts?

Cheers David

Post: # 103637Post **msh paving** Fri May 01, 2015 6:31 pm

i have several drives over existing concrete with no issues, never have drill concrete as its no different from laying on a lean mix base, but thats just my experiance MSH

mickg · Post: # 103639Post **mickg** Fri May 01, 2015 9:52 pm

water can seep through a lean mix but cant through wet concrete so it can lead to water saturation ending with the block paving starting to move, we have never seen it happen but I have heard it can and manufacturers recommend the process of core drilling and to fill the hole with MOT Type 1 and compact so none of the sand laying course can migrate down into the holes

rigid would be the best option making sure you clean off any surplus bedding material to eliminate any cement staining on the surface of the new block paving

like MSH we use a lean mix on a lot of driveways due to soft ground or if the home owner has a SUV or van being parked in the same position as it stops any issues from arising at a later date

it could be done the same way as setts are bedded into the semi dry mix but would take too long, better off screeding the semi dry mix to the correct height and fall and lay the block paving as you would the conventional way

David 1234 · Post: # 103659Post **David 1234** Sat May 02, 2015 5:06 pm

Cheers Mick and MSH. I've always wanted to ideally go for a rigid set up and Mick your method of screeding sounds easy. I was planning on doing this with a Rompox D1 joint. But so many people on this site warn against rigid construction because of possible cracking.
I don't know if there are movement joints in the concrete pad and I haven't lifted the pavers yet to see if the concrete has any cracks. In reality, is rigid construction likely to be risky? I really want to go for it if possible and I know it's worked for Mick. But so many past posts warn against it.

mickg · Post: # 103665Post **mickg** Sat May 02, 2015 11:12 pm

a rigid method is an unconventional way to install block paving what is normally laid using a flexible laying method therefore it's not to British Standard

Disclaimer
it does work but I cant endorse it as the correct way due to someone taking legal action if anything should fail

David 1234 · Post: # 103666Post **David 1234** Sun May 03, 2015 1:03 am

Blimey Mick are there really people out there who take advice from a friendly forum then threaten to sue for it? Unbelievable. Well it's not going to happen here - I'm just a bloke with a drive who has a mate who's a brickie who fancies redoing that driveway.

I saw a BS 7533 for rigid paving and it's not in the real world. It even specifies exact slump for the mortar, testing each batch before laying. Anyway in the real world I realise no one is likely to go to that much detail.

So what I really want to gauge and here's my disclaimer, if you give me advice and my driveway disintegrates and collapses down a bloody big hole I promise I won't sue you and any advice is taken at my own risk - so in the real world is it dodgy for me to construct a rigid driveway on an existing concrete pad that's been there since 1985 with no movement joints? Like if I do and lay my pavers correctly is that a real risk that they'll crack due to no movement joints?