Settlement on new drive - Block paving

[mikeozz]

Hi All,
Advice required before i speak to contractor.
Have had my block paved drive down for a couple of months now.
Drive was sealed with "keybond" or similar.
After driveway was complete went through a period of heavy rain, appeared to wash out some of the kiln dried sand.
Have now noticed that driveway is settling/channeling, particularly where the wheels of my car follow the drive.
Is this the likely result of losing some jointing sand or possibly poorly laid sub-base.
I plan to ask contractor to make good the settling - this has happened in a few spots on the drive rather than all the way up. My concern is that this may also appear over other parts of the drive over time.
How difficult a task is it to repair areas of sinking drive??
Appreaciate i have asked a lot here but want to make sue i`m prepared for my "chat" with the contractor.
Any help would be greatly appreciated.
Thanks

Mike

[GB_Groundworks]

without any pictures it would appear that the sub base was inadequate i.e not enough of it or wrong material or that they didn't compacted it throughly enough or both of the above.


if you could post some pics it would help

[Dave_L]

AS GB says - did you have a spec? What depth did they excavate to? What stone went back in?

All very easy for someone to do a quick job and make some cash, as most of their work is covered up!

[mikeozz]

AS GB says - did you have a spec? What depth did they excavate to? What stone went back in?

All very easy for someone to do a quick job and make some cash, as most of their work is covered up!

Thanks for response GB & Dave L.
Will take some piccies in daylight and post.
Not completely sure what depth of sub-base was installed.
The sub-base itself was a grey stoney material, layed ontop of fairly firm clay soil.
Addded to this was a good layer of sand prior to block laying.
Both sub-base and sand received good whacking.
Driveway is shared, neighbours side seems ok.
Piccies to follow.
Thanks again for responding

[williams]

Even on a well sub based drive you can get rutts if the sand washes out especially if its a strecher pattern.
He should of told you to top up the kiln if the rain washed it out.

Of course though it could well be a crap base:rock:

[mikeozz]

Even on a well sub based drive you can get rutts if the sand washes out especially if its a strecher pattern.
He should of told you to top up the kiln if the rain washed it out.

Of course though it could well be a crap base:rock:

Thanks for your response Williams.
Have today bought couple of bags of kiln dried sand and re-filled any empty joints.
Yor further opinion would be appreciated....
Contractor is calling round on Saturday, what should i expect him to offer in terms of making good the work?
i.e. where slight settling has occured should they be topping up sand base below block or digging down to hardcore level and applying more.
If settling appears say on a half metre stretch no wider than 3-4 blocks how much around this spot should also be removed and made good.

Thanks for advice so far.

mike

[williams]

It depends
If they have put down proper sub base then just ripping up the dip,laying a new bit of sand/or more sub base depending on the depth of the dip,compacting,laying blocks and then compacting blocks should suffice.

If the base isn't decent then there may be a problem.

[Mikey_C]

the blocks wouldn't be moving due to water logged bedding course would they?

[rom1]

hi all, my block paving has been down for just over two weeks and im struggling to get hold of the firm that did it! i got through once and they said they would come, but looking doubtful, as i have rang many a time! my block paving has settled into two areas where the trees were (probably 4 squared metres). they dug the roots rite out and placed broken stone inside with a grey sub base (looked like concrete), then black strong hardcore, then sand and blocks on top! the area is 140 metres squared and they dug 8 inches down, including the grassed area. is the settlement likely to get worse?

[Rich H]

Probably yes.

That 'black strong hardcore' is ringing alarm bells. It sounds like road planings to me which is a cheap but unsuitable and commonly-used pikey alternative to DTp Type 1, which is the only spec suitable as a sub-base (foundation) for paving.

[rom1]

a friend had his job done by the same firm 3 half years ago without the problem of sinking.

1)the overall digging was 200mm, in some areas 250mm.
2)they then laid a base of 70mm (a grey compound that was wackered and became solid).
3)sheeting was put down
4)once the base was down they put 100mm to 150mm of hardcore (which looks like road planings:( ).
5)river sand which was again wackered.
6)lastly the block were put down.

[Tony McC]

The short answer is that there shouldn't be ANY settlement in a matter of weeks. Settlement over a number of years is not all that uncommon with any flexible pavement, but if such settlement occurs within the first three months, that can only be due to partial compaction of one or more layers and/or poor sub-grade.

Whatever, it is the contractor's responsibility.