Block Paving

[Jonny112]

Hi, I am in the middle of having my driveway block paved but I am seriously concerned about the work being carried out.

Originally the planned work involved digging out, filling with crusher run and compacting before laying blocks.


Now the problem I have is the company carrying out the work haven't used crusher run but general rubble (bricks & stones). On part of the drive i can see there is very little rubble and just clay/soil.

I have asked the chap if there is enough hardcore to avoid sinking of the blocks, he assures me it won't sink.

They are due to start paving tomorrow and I am worried of future problems.

Can anyone advise what I should do before they start paving?

The biggest worry is once the job is done and they have been paid they will not return if there are any problems.

Thanks
Jonny

 

[noseall]

Unless block paving is done to a high spec it is likely to sink in areas of high traffic.

As well as a decent base, the paving needs well bedded kerbs or edge restraints. You often see dodgy companies laying the edgings on a bit of compo or even dry! These should be set on a decent concrete kerb race and be well haunched.

Really poor ground benefits from a layer of geo-tex to help stop localised sinking.

It's not only the sub base that needs compacting but the screeding sand needs a run over too.

 

[Jonny112]

Thanks for your reply. I know they are puting down some form of membrane to stop weeds coming through. I have this horrible feeling I'm being done over. Concrete restraints have been put in so I'm hoping holds together. It's the sinking I'm worried about.

Before they start paving I'm going to ask about guarantee of work and having it in writing. They keep telling me it won't sink but if I have no guarantee I'm stuffed once they complete. So worried about this.

 

[xdave]

Ideally you needed the guarantee before work began, but it's a bit late for that now.

I'm sorry to be the bearer of bad news but laying the sand on areas that are just clay will result in sinking - no amount of compacting will prevent that. The clay will expand and contract at best 10% and at worst it can be up to 30% and it can only move up and down. You will end up with a wobbly drive.

A firm of travelling drive layers moved through my street last year and laid blocks for half a dozen people. One has been replaced already - at the owners cost - and a couple of the others look like they were laid on jelly and have water retention issues. I feel so sorry for the owners because they were told one thing and the installers took them for a ride.

Rubble is no good as a sub base because it doesn't self-bind and being large has too many voids present no matter how much you compact it.

You need a continuous layer at least 60mm but ideally 100mm thick of a self-binding material that is well compacted in layers, or reinforced concrete with adequate drain holes, then a membrane to prevent laying course migration which is again compacted and then kiln dry sand or grit (depending on your paving) vibrated into the paving gaps to hold it all together. The membrane is structural and not to prevent weeds. It will need kerbs set on concrete - not mortar - to the spec noseall has stated.

In your situation the best you can probably do is to confront the boss with your concern that the drive is not being laid to any relevant British Standard and is virtually guaranteed to fail. If they are not prepared to put it right there and then, or to restore your drive to the original finish and walk away, then get a declaration in writing that if the drive fails within 10 years (in reference to the allowed movement under the British Standards) then the boss/directors of the company will be held personally liable for the costs of reinstatement to the British Standards. Do not accept corporate liablity because the company will just fold - you need a statement from the owners acknowledging personal responsibility for the liability. Ask to see a current driving license or passport and either take a copy or record the numbers and proof of a current residential address. BS allows for 10mm over 3m so you will have to accept that, but 1mm over and you would have recourse to either have it put right or bankrupt the owner through the civil courts.

If you decide to accept the drive then get in some local independant firms with good reputations to quote for laying to the same non-standard that your contractors have used and do not pay a penny more. A reputable firm will usually offer a 10-20 year insurance-backed guarantee as standard against any failure outside of the BS.

 

[cotswoldbuilders]

We would use 200mm of well compacted hardcore, vibro rolled and not whacked.

 

[^woody^]

The preparation and sub-base is the most important thing for block (and any) paving, but most people are only concerned with the colour of the paving and a nice pattern. Problems then only appear when the firm is long gone.

150mm of suitable hardcore will do for domestic drives, and crushed clean rubble will do if it is actually free from other debris and crap.

You don't need a weed membrane, but you may need a binder membrane (a geotextile material) to prevent rutting where you continually drive in the same place.

 

[Jonny112]

I have spoken to the bloke this morning. He is giving me a written guarantee. I think there will be rutting its just a case of will he keep his word.

 

[Hugh Jaleak]

Guarantee wont be worth the paper its written on unless there is an insurance company backing it up. Any firm can give a lifetime guarantee on their work/products, but if the company goes belly up 12months later, any promises they made are about as much use as a chocolate teapot.