Joined: July 2004
||Posted: 23 Feb. 2017,19:29
Like Sean, I don't think it's a sub-base problem, at least, not a sub-base depth problem, I'd be more interested in looking at the bed sand. If that is pumping-up via the joints, then either it's the wrong sand or it's degraded to the point at which it's useless.
How does your man plan to add 50mm of sub-base? It would elevate the repaired area, compromising threhold levels and, possibly, breaching DPC levels. And to add 50mm, he'd need to loosen at least 50mm of the existing sub-base, mix in the new stuff to get proper integration, then re-compact. Also note that the bed sand *cannot* be re-used.
For me, there's little point in re-laying until the cause of the problem is identified, and that, I suspect, can only be done by a careful assessment by someone with pavement engineering experience.
Site Agent - Pavingexpert