Patio drainage - Question about fall - drainage

[eskimo]

My builder has just completed a new extension, and a patio which buts up to the rear wall of the extension. The fall on the patio is zero in all directions, and the level is 100mm below DPC. He has not yet been paid for the work.

His proposed remedial action is to add a screed to give a 1:60 fall away from the house - which would take the height below DPC to 50mm - and to install a 100mm wide French drain along the house wall.

Is this a reasonable approach, or should I insist that the concrete is taken up and relaid with the correct fall, and stating from 150mm below DPC? I don't really want the maintenance liability of a French drain, and am worried it may turn into a moat.

Any advice or views gratefully received.

Eskimo

[lutonlagerlout]

oh dear
any and all builder should know that finished ground level has to be 150mm below dpc,apart from certain situations ( the job we are on at the moment ,we are tanking because ground level cannot be reduced anymore)

building control will allow 100 mm below dpc if an aco is used running to a suitable soakaway or drain and the patio is falling away from the aco

if he has laid it flat, it is wrong and must come up,if he has got his levels wrong then he must dig some more out and start afresh

french drains ==> a hole filled with shingle ==> not worth a carrot

LLL

[irishpaving]

how could they get it wrong its new.

[Bob_A]

His proposed remedial action is to add a screed to give a 1:60 fall away from the house - which would take the height below DPC to 50mm - and to install a 100mm wide French drain along the house wall.

I'm a bit confused. Apologies if I've got this wrong.

If you have a 1:60 fall away from the house why would you need the drain at the highest point along the house wall.


Surely the drain should be at the lowest point.
If so would this be better
http://www.pavingexpert.com/drain14.htm

[Stuarty]

I think what is meant Bob is so the patio doesnt sit tight to the blockwork and is to prevent splashback. Although the only way to rectify the mess is to rip it up imo. Cant see why anybody would build a patio spot level. Seems as though things werent thought through, or it was more a case of "well be long gone by the time he notices"

[eskimo]

I think what is meant Bob is so the patio doesnt sit tight to the blockwork and is to prevent splashback. Although the only way to rectify the mess is to rip it up imo. Cant see why anybody would build a patio spot level. Seems as though things werent thought through, or it was more a case of "well be long gone by the time he notices"

Yes indeed - the "French drain" is just to prevent splashback.

Thanks for responses so far - there seems to be a certain unanimity that it should be ripped up and started again. I only wish building control would be so definitive - they say they are prepared to sign off on the French drain approach, despite telling me that they regard it as a "bodge" of last resort.....

[Bob_A]

I think what is meant Bob is so the patio doesnt sit tight to the blockwork and is to prevent splashback.

Aaah I see, sorry for the interruption.
Just here to learn

Edit
This might worth a read
http://www.pavingexpert.com/dpc01.htm

[henpecked]

they say they are prepared to sign off on the French drain approach, despite telling me that they regard it as a "bodge" of last resort.....

Unbelievable!

Building control/world of their own.

:laugh: :laugh:


Hp

[Tony McC]

This is the second job in as many months where I've heard about or seen a patio constructed by a builder has been laid dead flat. It's damned hard work to lay anything dead flat, but with so many brickies being out of work, more and more of them are moving into the patio and driveway market and bringing their obsession with "level" along with them. Brickies rarely, if ever, lay to a fall, so some of them just don't understand how and why a patio or driveway would need a fall.

As for Building Control, they have no interest in patios. There are no official documents to tell them what to think, other than the bit about DPC levels in part C, so they never know what's right and what's shite.

[eskimo]

Tony,
Thanks for this comment. It is interesting to note that our builder did delegate the patio job to his brickie, who was responsible for deciding all the levels.
Eskimo

[lutonlagerlout]

is it pick on lagerlout weekend? :;):
I'm a bricklayer and i understand the need for falls

see ? there is a god

LOL


LLL

[Tony McC]

Yeah, but you're a redeemed brickie, LLL, one of the few that can tie their own bootlaces and understand falls. Not all brickies are like that, you know! :p

[seanandruby]

Yeah, but you're a redeemed brickie, LLL, one of the few that can tie their own bootlaces and understand falls. Not all brickies are like that, you know! :p

Not so sure about that boss, he wears riggers boots. Maybe the falls he understands...after a few sherbets :laugh: