The Brew Cabin

Posted: **Tue May 10, 2011 5:26 pm**

192m2 drive currently tarmac (flat ground/ gently falls away from house to large garden) installed 1960's. Ive dug two test pits 250mm x 250mm x 250mm to look at the drive stratification. Top layer 50/60mm tarmac, 2nd layer hoggin (sub-base) 150mm, followed by sub-soil (made up of clay and flint).

The customer would like to replace the drive with 10mm marine gravel with a granite sett edging and crossover. Ive suggested removing the 50/60mm tarmac, laying a geotextile membrane and laying the gravel on top.

However, the customer has mentioned a soakaway and he has also been quoted by another contractor that he requires a soakaway.

I'm really after a second opinion. I don't think he needs one. The tarmac drive currently doesn't flood, the sub-base is permeable and the drive is fairly large and should be able to cope with a deluge of rain comfortably. The fact that the customer has questioned me has made me question my advice. So, a second opinion would be appreciated.
thanks

Posted: **Tue May 10, 2011 7:35 pm**

if the subbase is freeflowing why would you need a soakaway?
by law any impervious drives need SUDS now i.e. bitmac,CBP,RBG

show your client this
document

you are correct
LLL

Posted: **Tue May 10, 2011 7:46 pm**

A gravel drive doesn't normally need any additional drainage especially if the lawn has been coping with the runoff until now. I would strongly advise against a membrane between the subabse and the gravel they always get exposed over time and tear and fray and look awful. Also the gravel grips and binds with the subbase helping prevent migration. The gravel size is possibly going to cause problems to because it'll be picked up by tyre and shoe treads very easily and will scratch the floors and be deposited on the highway.

Posted: **Tue May 10, 2011 9:19 pm**

Agree with Pablo on all points!

Posted: **Wed May 11, 2011 6:40 am**

only problem i can see is if you lay the gravel to deep. Everything else is good.

Posted: **Wed May 11, 2011 9:38 am**

Thanks for the advice. Always worth checking someone elses opinion.
I have to say i wasnt sure about the membrane myself for exactly the reason mentioned (unsightly if exposed) Otherwise thanks. The gravel shouldn't be toomuch of an issue as the gravel stops at the crossover point which is some 25m or so from the main road. The size of the gravel is by request, in other words thats what the customer has asked for! I have to say, that I prefer the smaller gravel, yes it does get picked up in car tyres and can end up on the main road but i'd rather the drive look like a gravel drive than a pebble beach!! i installed a gravel drive last summer, actually about the same size as this one and only just about a mile up the road and they wanted the 20mm gravel. It looked ok, but alittle pebblely.

Thanks for the advice, much appreciated.

The Brew Cabin

Another soakaway question im afraid!!