Renewing an old drive. - 1 layer or 2?

[T/R]

This is my first post, I hope the experts can advise!

It's a 175 m2 domestic drive, laid in 1967.
There is a turning circle so a risk of power steering scuffing.

We've had on site concrete lorries and JCBs running on it with no effect, the base construction is 250mm of broken concrete and rubble with 150 mm of ballast over.
Solid - when we chased across for setts we had to use a jigger pick to loosen the stuff, hand picks just bounced off!

The 1967 surface appears to be one course 50mm thick, a mix of between 6mm and 20 mm stone in the Bitmac / Tarmacadam.
Trouble is the surface has just got old and tatty, needs replacing.

I've had a few quotes - same kinda money £6 - £8 k.

Some say dig out 100mm (top + 50mm into the ballast) then 70 + 30 mm courses.
Fine, this is the straightforward way of doing the job.

But one guy, whose work we've seen, came across and said "Don't disturb the ballast, it's great. It's done it's job for 50 years - take off the existing 50mm and simply lay the same thickness of 10mm hard stone SMA".

My gut feeling is this is sensible, replace like for like and leave the excellent base material well alone.

What do those in the know think, please?

[Dave_L]

I'd sweep it clean, tack it and regulate it to level and then overlay with a 35mm thickness of AC10. Impossible to quantify the regulating without seeing the job though.....

[T/R]

Thanks Dave.

Problem with that is the existing ( well set and in good condition) kerbs wouldl be below the new surface, along with the garage floor slabs.
The new surface levels have to be as existing - so something has to come off!

I'd just like some confirmation the 50mm of SMA approach is good enough to last, or I'll have to chicken out and let the other guy start ripping up the ballast ....

[Dave_L]

Sorry; I missed that point - yes take off 50mm or so, sweep clean and overlay with 50mm of 10mm SMA yes thats fine. I wouldn't expect 50mm to be laid in one go - maybe 25/30mm of regulating where required to achieve an even grade (remember the finished product will only be as good as the preparation below) and then the remaining 30mm or so to top it off. Job done

[T/R]

Sorry Dave, just realised you may mean take off the existing not lay new course on top of it!

If that's right it sounds like you are confirming one good quality course will bo the job.

[T/R]

Dave,

Ignore last ramble - I was typing it as you added the reply!
They overlapped.

Great - I appreciate the second opinion!

I'm realistic enough to expect we'll only know exactly what's happening when the machine's taken the existing off.

Thanks again for the advice!