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Posted: Fri Jun 20, 2003 3:39 pm
by 68-1093879222
Is there a standard recognised Specification for laying Marshalls Tegula Driveset. My contractor recommends concreting in the edging as opposed to the last row of blocks - any comments. He also recommends a poythene sheet under the hardcore - is this necessary? And finally his price is 70 pounds sq meter including material - does this sound reasonable (I am getting other quotes)?
Posted: Fri Jun 20, 2003 3:59 pm
by 84-1093879891
Tegula Drivesett are laid in exactly the same way as any other concrete block paving. As long as the edges are properly restrained, it doesn't matter whether a kerb/edging is concreted-in or the edge courses themselves, as long as they are solid, do not move and can withstands the loads imposed on the paving.
However, this idea of using a polythene sheet is a Class A Indicator of a Dodgy Contractor. Polythene should never, ever, ever be used beneath block paving. It is the sort of gob-shite idea put forward by eejits who think they know how to lay block paving, but really shouldn't be allowed out of the house unsupervised, because they cannot tell the diff between a sheet of polythene and a geo-membrane, and don't understand the reasoning behind the inclusion of geo-membranes in
certain constructions.
Here's something from an up-coming web-page on this very subject...
So, a weed membrane is not necessary beneath a properly constructed pavement, and the suggestion put forward by some well-intentioned but misguided bodgers that a sheet of polythene or similar can be used in placed of a permeable membrane is a certain recipe for disaster. Polythene is impermeable, which is why it is used as a damp proof membrane in buildings, but to use it beneath an elemental pavement (block paving, flags/slabs, setts, etc.) will prevent the proper drainage of the pavement layers, which will, in turn, lead to saturation of the bedding layer. With unbound bedding materials (grit sand, etc), this can have the unfortunate effect of causing the paving layer to ‘float’ as the bedding material begins to act like a fluid. For this reason, impermeable membranes are not to be recommended beneath block paving, patios etc, unless some other form of sub-surface drainage is present.
However, the use of permeable membranes beneath elemental pavements is becoming more popular and is a perfectly valid construction. Their manifold uses and applications are covered
elsewhere on the website, but their primary purpose is to add stability to the construction, not to prevent weeds.
70 quid per square metre had better include all materials and VAT. I'd definitely get at least 2 more quotes if only because the notion to use a polythene sheet beneath the paving worries the pants off me. :(