The Brew Cabin

I live in a house that is at the top of a very steep drive (about 45 degrees). The driveway was constructed 2 years ago and comprises of two rows of 3x2 concrete slabs layed end to end embedded in concrete. The slabs cover the route taken by the cars wheels and hardcore is positioned between and outside the slabs so that the width of the drive is about 8'. The ground is very rocky and drainage is not good (although rainwater seems to drain through the hardcore ok). The grass on either side of the drive can become very wet and soft during wet periods.

We dislike the look of the drive at the moment and would like to replace it with clay block paving that we think looks much more attractive. I however have 2 concerns:-

1. Because of the steepness of the hill and because the cars enter the drive at an angle I am concerned that the block paving might 'move' given time. Is this likely? Could the whole area of paving be surrounded by concrete (as the 3x2s are at the moment) to prevent movement ? I have been looking around now for some considerable time and have never seen a drive as steep as ours with block paving.

2. We live on the south west coast of Scotland where it rains a lot - especially during the winter months - and it can be damp. I understand the clay blocks can be affected by moss etc. moreso than the concrete blocks. I am concerned that due to the slope and poor drainage the water might drain 'down the hill' and over the blocks rather than between the blocks thus making the moss problem worse. Is this likely ?

We really do like the look of the clay blocks, however if you feel they are unsuitable for our circumstances what surface would you recommend ?

Thankyou for any assistance.

I've just realised that the steepness of the slope I quoted is wrong. The drive is approximately 24 metres long and in that distance drops about 5 - 6 metres, with the gradient at the bottom being slightly steeper at the bottom than at the top. So I suppose the gradient is about 1:4 at worst - nothing like 45 degrees! - but still quite steep.

Portpatrick asked...

Could the whole area of paving be surrounded by concrete (as the 3x2s are at the moment) to prevent movement ?

The perimeter of a clay brick (or concrete block) driveway should always be laid on and haunched with concrete. There are exceptions, but they are few and far between.

In your situation, I would insist on a firmly bedded and haunched edging course, particularly at the bottom and the sides.

I am concerned that due to the slope and poor drainage the water might drain 'down the hill' and over the blocks rather than between the blocks thus making the moss problem worse. Is this likely ?

It's more than likely; it's absolutely certain!

Despite what seems to be a common misconception amongst members of the public, surface water does NOT drain through the joints of block paving. There's a study been done by the TRL (IIRC) and they calculate that 98% of the water that lands on a flexible block pavement will run-off - only 2% finds its way via the joints to the laying course and sub-base. Surface water does NOT drain through a block pavement. Some provision for colelction and disposal of the SW must be made - gullies, linear drains and/or channels will be needed.

However, as you correctly state, clay pavers can be particularly prone to mosses, more so than concrete pavers, and not just the joints, but the surface of the pavers itself. Now, given the very steep nature of your driveway, this will be countered to some extent by the water cascading over the pavement during the wet weather. Once the slope of a block/brick paved driveway gets above about 1:10, a sort of self-cleansing property becomes apparent, and mosses, algae and other vegetation find it hard to survive. That's not to say they find it impossible, just harder than it would be on, say, a 1:60 driveway.

This is easily remedied, though. Use of a quality urethane-based sealant will counter colonisation by mosses and other weeds, and, more importantly on your steep drive, will prevent the essential jointing sand being scoured out by the run off.

My opinion is that you should have no qualms about using clay pavers for your driveway. Laid properly, they will outlast us all, but I can't recommend too strongly the use of a quality, tested-and-approved sealant, not just to maintain its good looks, but to ensure its longer-term structural integrity.

One last point - you may want to consider using rigid construction for your driveway, rather than flexible. I can't say which is more appropriate without being familiar with the site, but it's certainly worth interrogating your contractors when you get them round to price up the job. A steep driveway in clays is a prime candidate for rigid work.

Thanks for such a prompt and informative reply. Your site is crammed full of useful information - especially for folk like me who do not have much of a clue.