The Brew Cabin

I am about to lay a 125mm sub base direct onto clay prior to block paving and have been advised to lay a (weed prevention) membrane under the hardcore first. I am unsure as to whether this would have any benefit. A colleague said he has just had his drive block paved and a similar type of membrane was laid between the sub base and the sand top dressing?

Have just noticed all the other pages on the site re the block paving forum, and I think now that I've seen the other replies on this exact subject (don't know how I missed them) I shall keep my pennies for a bottle or two when I've done the drive.

Good idea! :)

There's a subtle difference between 'weed membranes' and geo-sheets. The former are intended to keep out the dandelions and the like from gravelled areas, while the latter are a structural layer performing an important function within a pavement. You might use a geo-sheet at the boundary between the sub-grade and sub-base if there was a problem with the condition of the ground, but there is rarely any need to install a weed membrane beneath a block pavement that has a 100mm sub-base. The one exception is when there are pernicious weeds, such as Equisetum spp (Mares Tails) or Polygonum spp(Japanese Knotweed) and even then I'd much rather specify a geo sheet, on grounds of inherent strength, than a weed membrane.

99% (roughly) of weeds can not grow through a properly constructed block pavement, but even a weed membrane will not stop them growing into a block pavement, anchoring themselves in the sand-filled joints.

Weed membranes are, in almost every case, an utter wate of time and money when used beneath block paved residential drives and patios.