Three quotes - three contractors disagree

[David 1234]

I've had three quotes for my 85 square meter driveway but the specs are totally different. Existing driveway is block paved sitting on 35mm sharp sand on 100mm concrete pad. There has been some movement on the existing driveway - not awful but noticeable.

Quote 1 - retain concrete base and blind over with Type 1 where necessary, lay 30mm sharp sand, screeded and compacted.

Quote 2- retain concrete sub base, screed with lean mix over low points, screed with sharp sand as normal.

Quote 3 - Install geo textile over MOT type 1 150mm compacted. 50mm sharp sand screeded and compacted.

Contractor 1 - this guy's an Interlay contractor so this really surprised me. He wants to retain the sub base because I have a low single skin wall sitting on the same foundation as the driveway and he's worried that it will be shaken and damaged whilst breaking up the concrete. What surprised me is that he recommended adding type 1 to a concrete sub base.

Contractor 2 just likes concrete sub bases and thinks that it would be unnecessary to break it up and is certain that if he screeds over any low points with a lean mix of concrete then the pavers will not move.

Contractor 3 wants to create a new sub base to a usual spec and isn't worried about damaging the wall and said that he's grind out the edge of the concrete base next to the wall so not creating too much vibration.

I know that building a flexible driveway on top of a concrete sub base goes against all usual specs. But I also know that many old driveways still perform well using that very specification - I recall LLL on this forum mentioning that. Gents, what do you think? Are quotes 1 and 2 doomed to failure and will Quote 3's breaking up the existing concrete base really shake the wall sitting on the same foundation to death, even if carefully cut out?

Any opinions very welcome thanks! All three contractors have given conflicting advice.

[dig dug dan]

Quotes 1 and 2 are looking for an easy way way out of doing the main bulk of the work, and the core structure of the drive,,which will eventually lead to the drives core strength and rigidity
Quite 3 is the right way to go. Block paving is designed to be flexible, and not laid on concrete.
As an example, every time you see block pavers laid as they should, then laid round a concrete manhole, after a few years, the manhole always appears to be slightly higher. That's the non flexible part!

[Tony McC]

There *are* methods of laying flexible block paving over a concrete base, but neither of the first two specs seem to address this....

https://www.pavingexpert.com/blokbase

....while the 3rd option is a whole new construction.

Option 1 I find unacceptable - you cannot regulate a concrete base with Type 1 aggregate. The minimum workable thickness for a Type 1 agg is....at an extreme push....50mm, but I would be very, very reluctant to ever use less than 80mm. If the existing base is only out by, say, ±20mm here and there, then Type 1 will not be suitable. Could a smaller agg be used? Well, it could, but it wouldn't be suitably load-bearing in the way that Type 1 is designed to be.

Option 2 is more feasible - use a cementitious overlay to regulate, which would allow as little as ±6mm to be corrected, but every millimetre of regulating pushes up the finished paving level by one millimetre, so regulate, say, 30mm, and the paving ends up 30mm higher than it was.

And there's still no mention of how water finding its way into build-up will be managed.

Option 3 is, as already stated, a whole new build, which is fine, but possibly unnecessary.

My solution would be Option 2 will added drainage, either as a horizontal drainage composite (waffle board) or core drilling through to a permeable sub-layer. The depth of the laying course may have to be reduced to ensure finished paving level remains acceptable, but, of the 3 options, this seems the most straighforward to me.....but bear in mind I haven't seen the site.