Dips in 9 month old drive - Advice please

[Spongebob]

Hi All,

Hoping for some advice from all those with more experience and knowledge than us....

The drive was laid September 2013. We noticed in March that some blocks seem slightly higher than others. We mentioned this to the contractor who said they might need whacking down again. (This hasn't been done). Recently we noticed some of the lines of paving appear to dip slightly, so we spent the morning with a long spirit level (to use as a straight edge). We found that where our car tyres track, from the top of the drive down to where we park, the blocks have sunk.

It's difficult to see (to our untrained eyes) when just looking at the drive. But using the straight edge we can see the blocks have sunk by up to 15mm, where our tyres run. It's on a slope so there are no puddles when it rains.

This isn't supposed to happen, is it? Especially after 9 months? Or could he reasonably say this is normal?

We've searched through the very helpful info on this website and forum, and we're thinking something is not right with either the sub base, the sand, the compaction or maybe all of these! Obviously will need more investigation....

We have not called the contractor yet, but we'd like to be prepared before we do. What are your thoughts?

Will try to post a pic of the dip....

[r896neo]

It could be a few things, wrong type of sand, too much depth of bedding sand or worst a defective or inadequate sub base.

Was there a specification with the quote on depths of sub base sand etc?

The sub base could be not deep enough or not well enough compacted.

Was it laid by a reputable contractor?

[sy76uk]

There is always some settlement in paving but what you are describing sound too much.
If you have dips it doesn't need wacking again. The area needs to be lifted and re-laid.

The main question is, why has the are sunk in the first place. The answer in most cases is either not enough hardcore has been used in the sub base or too much sand has been used in the bedding layer.

I had a job last year that had sunk where the clients big Audi usually tracks.
I had used around 200mm of MOT type 1 for the sub base that had been compacted in 100mm layers and 25mm of sand for the bedding layer.

I was amazed when I got the phone call about the problem but I went straight out and sorted it the next day.
Luckily the client was a retired groundworker so he didn't accuse me of cutting corners on the installation and I've had 2 jobs come through from friends of his since then.

Lifting and re laying small areas is not a big deal for any contractor. The beauty of block paving is that it is very easy to repair so even if the contractor does mess you about, it shouldn't cost you much to have another contractor put it right.

[Spongebob]

Thanks for your early replies.

Just posting a link to photo.
Don't shoot me if it doesn't work!

http://instagram.com/p/ota8bZPHCY/

http://instagram.com/p/otc0YivHF2/

Ps yes good guess my wife does have an audi but it still dips where I drive the ford focus.