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Posted: Wed May 17, 2017 3:44 pm
by ian-rug
I was sent the DPC page to a customer and he noticed that the 150mm rule was (among other things) to reduce the incidence of 'splashback' from rain and has a image illustrating what it meant.
However at the bottom of the page where it covers the Linear Drain option it says paving may be laid to within 75mm of the dpc, or even closer if used in conjunction with a step or access ramp.
How does this remove the "'splashback' from rain" issue given the grating of most Linear Drains have less hole than surface so will create almost as much 'splashback'.
I know its a annoying question but its one he wants answering with more than a "who cares the regs say its ok"...
Posted: Wed May 17, 2017 7:44 pm
by lutonlagerlout
its a real world solution
sometimes you have to work to best practise and workarounds the BCO local to me are happy with a linear drain 75mm down from DPC if it is not possible to get 150mm down
loads of conundrums in the building game like this
LLL
Posted: Sat May 20, 2017 3:00 pm
by Tony McC
The 'splashback' theory is based on an idelaised situation, where it would be wonderful if we could always stick to that guidance, but the real world, as LLL says, is a matter of compromises, and so, occasionally, the rules have to be massaged to take account of what we are faced with on site.
It would be wrong to install to 75mm below DPC as standard practicem but when there really is no other option, it's better than being, say, only 50mm below DPC.
The Building Regs are deliberately vague to enable 'interpretation' to facilitate local preferences, materials and site conditions. For more than 30 years I have been trying to get a definitive statement as to what is or isn't acceptable but each local authority has their own chief BCO who will put their own interpretation onto matters, and so what is 'permissible' in Town A may not be welcome in City B and vice versa.
However, in general, if you have a valid, logical and credible explanation as to why your particular "workaround" was used rather than strict adherence to B.Regs, then *most* BCOs will give it the nod, but if they think for one second that it's an excuse for laziness or incompetence, they can make your life very difficult indeed!
Posted: Sat May 20, 2017 8:09 pm
by lutonlagerlout
things like gas mains, or other pretty immovable features normally make them take notice to work arounds
also rainfall differs all over the country
different rainfall in east anglia to cumbria 
LLL