This raises a few points worth thinking about .
1. Block paving is just the surfacing , and will reflect what is underneath , hence settlement if the stone sub base is not flat , or the sand is more than 50 mm thick , or say an old drain trench settles .

2. It is much easier to lay blocks on so called concrete [ often just cement and sand ] than it is to put in the correct stone sub base and properly compact it, then correctly screed the sand and lay the blocks .

3 . Weeds in block drives are generaly from seeds from the top , not underneath , another reason given for the concrete .

4 . A correctly constructed block drive does not need 'concrete' ( I have supervised hundreds to NHBC standards . This however depends on the drive being constructed in the correct layers and course thicknesses , and the correct compaction equipment being available [ a small whacker is no use ]

5. In the situation where it is a lift and relay , with an ' irregular' sub base, and cost is an issue , then a there is some point in using say a 10mm sharp sand / agg . dry mix with cement, as the screed , after it has had a good roll with a bomag roller , but only to avoid the cost of complete sub base replacement.

6 . A lot of block companies only use a little whacker , and depend on the 'concrete' to take care of any dips in the sub base .

7 . A lot of drives lifted during the big freeze in the winter due to cheap none frost free stone being used as sub base [ should be type 1 stone ]. Often existing drives have no stone at all ! just a bit of sand under the blocks .

do not lay it on sand/cement and do not lay it on a concrete base unless there are issues with the ground itself. always dig out to the correct depth and use the correct grade of stone if the ground is soft or at risk of movement. some companies are fly by night. they install within 3 days and the driveway looks great but in a years time those same driveways look very old. pay for a middle range quote and get everything in writing as to what materials and what depths they have dug out to. also if the drive has sunk it may just be a simple case of over usage and age. nothing lasts for ever. strip the block and dig test holes for depth of stone and stone. if all is well then dig off old sand and discard, re compact the ground with either a heavy duty wacker or a bomac 80 road roller, then resand it, screed off and relay the blocks.

it does not need to have a concrete base as the only reason for your sunken sections of drive is because the job clearly wasnt done properly and whoever did the job didnt put in the required amount of hardcore and then to whacker the sand on top of the hardcore is necessary and not all builders will do this but it is vital for the drive to withstand the weight of cars. A good job done will last years and will not sink.

Block paved driveways do not necessarily need a concrete sub-base. Normally 200mm of type 1 hardcore will be enough as a sub-base as long as its wackered or vibration rollered to compact it. Then the sand and blocks can be laid with confidence that the drive will not sink.

never have a concrete base under block paving they will move ,dig out existing ground to 250mm depth ,compact and apply weed control membrane 150mm of type 1 compacted sand blind and compact ,sharp sand screeded to desired level plus 5mm ,lay 60-80mm drive blockpaving of choice,cover with a good layer of kiln dried sand and compact to level,rough guidline expect to pay 80-120 pounds per square metre ,price depends on access ,ground conditions ,drainage required ect
regards mitch
substructure

Because block paving works upon compacted surfaces pushing against one another, It is NOT necessary to concrete a base. If the existing has sunk in places, it is because it was not installed correctly in the first place. Terrain membranes should be used over soft ground, or ideally the soft ground removed and replaced with well compacted hardcore, overlaid a terrain membrane then with MOT type2(scalpings or crushed concrete) compacted again,concrete in the edgings to contain and next compact Sharp sand before screeding. This is then ready for blocks.
I have installed many drives and roadways with this method and all are still there today with no problems.(some more than 15yrs later).
Following people who have concreted on slopes...I have known the sand under to wash out!

You shouldnt need a concrete base under brick paviors, if the ground preparation was done correctly ie, excavate down to allow minimum 200mm of good clean hardcore over terrain fabric, vibro rollered and not with a whacker plate, lay flooring sand well compacted, screed to desired level, lay the paviors, run the whacker over with kiln dried sand, job done.
You would only need to go deeper with more hardcore if you are on soft ground.

Hi,

Its not a must to have concrete base If the sublayer of scalpings/type 1 or other hardcore component is done propelly.
its have to be compacted well, the same with sharp sand. There should be edges or other borders to keep it in on their place.
Regards
Jacob

hello it seems to me if your drive is sinking in places means that it was not laid on concrete in the first place if it was this would not have happened if you want peace of mind lay on conrete or sharp sand and cement. get more quotes dont rush some one will give you a reasonable quote some were in middle .

it does not need to have a concrete base as the only reason for your sunken sections of drive is because the job clearly wasnt done properly and whoever did the job didnt put in the required amount of hardcore and then to whacker the sand on top of the hardcore is necessary and not all builders will do this but it is vital for the drive to withstand the weight of cars. A good job done will last years and will not sink.