Block paved driveway dipping

Question

Hello
I had a large area of my garden block paved a few months ago. It looks great but I have started to notice some dipping in 2 areas. Its not a big worry but I am slightly concerned if it begins to get worse. I have spoke to the company that installed it and they're coming to take a look next week. I just want to make sure they don't do a bodge repair. 
What should i be expec ting them to do? I understand that block paving always dips slightly but this seems like a bit too much so early on. It seemed like they did everything right originally but i'm no expert. What should I expect there to be under there in terms of a base?
Any advice would be greatly appreciated.

Chris · Accepted Answer

Sounds like they didn’t dig down enough for stone & dust. You should be looking for between 150-200mm of stone 50-70 of dust. They should lift what’s sunk, raise the level of dust with more dust and compact.

Garry · Answer

Firstly, the block paving shouldn't have sunk or dipped at all. Secondly, have they put enough sub base stone in and deep enough, depending on what the original dug out ground was like? Thirdly, they need to lift up blocks, re-screed with screed sand, compact and relay the paving blocks. Have they compacted the ground enough, that is the question?

Michael · Answer

Originally sounds like a bodge job there shouldn’t be any sinking when the area was excavated this would have been noticed but they would have just brought mot in and wackered over the soft spots so they need to come to dig out the ground underneath the mot sub-base but they won’t they will just come out more sand underneath. To raise the pavers will be a temporary fix

Georgie · Answer

From what you have said I would say they haven’t laid enough depth on the sub-base/type 1
I would request that the lift the whole area and set aside what is installed but dig down a minimum of 150mm and install the membrane and type 1 and compact the correct depth, it shouldn’t be sinking shortly after installation and this is a key sign that you will have problems further down the line.

Stephen · Answer

The reason of this could be either the sub base isn’t strong enough under the sharp sand or there is to much of a depth of sand. 
They should take up the area that is dipped, re-prep and re-lay and also compact afterwards.

Steve · Answer

Dipping is generally down to the sub base not having the correct compaction and/or the correct depth.  It may be that there’s not enough sub base or too much sharp sand used.

The company might suggest re-doing the sections where you park your car but this isn’t ideal.  I would request that they lift the complete drive and put a new base down, compact it with a whacker plate and relay pavers.  This is the only way that you can guarantee no future problems unfortunately.

Adam · Answer

It sounds to me that the sub base has not been correctly compacted. There should be no dips in any of the new work carried out and should be laid on sand screed not exceeding 30mm

Damian · Answer

Hi Kelly,
Once the block paving is removed there should be a minimum depth of 150mm of compacted stone. Then a minimum depth of 50mm compacted sand. They should uncover affected area plus a little more then remove the sand and make sure it has the required compacted depth of 150mm stone. Then replace the sand and compact it to 50mm, screed it off and then replace the blocks. Then pour kiln sand on top and then compact and brush in. 
All the best.

Chris · Answer

May need to be lighter and ground peeped again with more stone

Andrew · Answer

Hi Kelly, from I reading I would say that the sub base and sand hasn't been compressed properly with a whacker plate. My guess is if it's dipping then the whole of the sub base needs laying properly and compressed with a whacker then sharp sand layer down, screed and whacker. That's what I would expect them them to do anyway and if I was you I wouldn't take any less. Good luck Kelly hope you get it sorted

Block paved driveway dipping

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