I'm building a patio using slabs (flags) - the area is 35ft by 11 ft, and a friend mentioned that it's a good idea to put a polythene sheet on the soil before I lay the hardcore/sand-cement mix.
Apparently, it reduces weed growth. Can you please offer any advice on this? Should the sheet go before the hordcore, or in between the hardcore and the sand-cement mix?
Many many thanks
Using membrane/polythene sheet in patio
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84-1093879891
There's absolutely no need to use a membrane, polythene or otherwise, beneath a patio unless there are specific problems, usually seriously bad ground conditions or deep-rooted pernicious weeds. I'm afraid this obsession with membranes is becoming an urban myth - how do you reckon we managed to build drives, paths and patios 20-odd years ago before membranes were popular?
They do have their uses, but I reckon 95% of all patios have absolutely no need for a membrane. If you are constructing with a sub-base (what you refer to as 'hardcore') and then a cement-bound laying course, and a 35-50mm thick flag/slab, then only something like Japanese Knot Weed will be able to find its way through that lot!
Further, the vast majority of weeds on patios and driveways don't come from beneath the paving; they grow into the paving from above, by colonising the joints and sending roots into any little fissures they can find. No membrane can stop that happening!
Have a read of the geo-membranes page, and the Landscape fabrics page, and that should help explain further.
Unless you are on boggy or made-up land, or if you're using a particularly open sub-base (ie, one with a lot of voids) there is probably no reason whatsoever to use a membrane, unless you like wasting money. :)
I've built over 1,000 patios since 1988. I've used membranes on two of them, that's less than 0.2%. With driveways, the incidence rises to around 1.5%, but that's still the exception, rarther than the norm.
They do have their uses, but I reckon 95% of all patios have absolutely no need for a membrane. If you are constructing with a sub-base (what you refer to as 'hardcore') and then a cement-bound laying course, and a 35-50mm thick flag/slab, then only something like Japanese Knot Weed will be able to find its way through that lot!
Further, the vast majority of weeds on patios and driveways don't come from beneath the paving; they grow into the paving from above, by colonising the joints and sending roots into any little fissures they can find. No membrane can stop that happening!
Have a read of the geo-membranes page, and the Landscape fabrics page, and that should help explain further.
Unless you are on boggy or made-up land, or if you're using a particularly open sub-base (ie, one with a lot of voids) there is probably no reason whatsoever to use a membrane, unless you like wasting money. :)
I've built over 1,000 patios since 1988. I've used membranes on two of them, that's less than 0.2%. With driveways, the incidence rises to around 1.5%, but that's still the exception, rarther than the norm.