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Posted: Tue Apr 01, 2008 10:19 pm
by Richey
Hi, have just finished reading all about retaining walls and still need a little help!
Does the 80mm diameter collector drain at the base of the wall need to flow into a catch basin or soak away or is it just there behind the wall acting as a sump to relieve the wall from a build up of water pressure. Naturally I will be including weep holes when I come to building my wall.
Why does a free standing wall need a damp proof course? What am I protecting by including one? And is anything bonding the course of bricks directly below the dpc membrane to the rest of the wall apart from the weight of the bricks above?
Finally...Is a dpc needed if using Marshalite Walling Blocks? I've never seen one.
Thanks to anyone who replies
Richey
Posted: Tue Apr 01, 2008 11:43 pm
by matt h
The answer to your questions is yes,
stops water rising up the wall and eventually weakening the wall through frost damage etc
DPC is bonded to both courses above and below and is assisted by the weight of the courses above, and marshalite blocks should have dpc course, but have seen several garden divider walls constructed without them
Posted: Wed Apr 02, 2008 2:15 am
by lutonlagerlout
Icould be wrong,and i have built maybe a 100+ retaining walls but i have never put a dpc in one yet.
we use sulphate resisting cement 3:1 ,but why would we need dpc in a free-standing wall that is subject to the elements?
obviously you need an f1 or f2 brick or walling block for retaining walls.
it breaks my heart when i see walls built with LBCs, there is a particular one in luton that was built about a year ago,its cracked already and i am waiting for the frost to get hold of it,when i replace my cybershot i will take a photie of the imminent failure
cheers LLL
Posted: Wed Apr 02, 2008 8:44 pm
by Rich H
Tony, you'll probably not be pleased to hear that I've built another LBC wall in the same street as the last one! The customer asked me to build them a drive just like the one up the street! And I repaired the neighbour's wall. I did at least explain that the same would happen to the walls in time, but they both wanted to keep the look as before...
Posted: Thu Apr 03, 2008 9:50 pm
by lutonlagerlout
i consign you to hellfire and eternal damnation rich!!
you can lead a horse to water, but you cant make it drink
at least your way it will give a brickie some work in 10 years time 
LLL
Posted: Fri Apr 04, 2008 6:35 pm
by Rich H
You see, every ones a winner
Posted: Fri Apr 04, 2008 7:43 pm
by Richey
Thanks for all the replies, however thickie here still doesn't quite get it.
Matt, when you said "The answer is yes" what were you saying yes to... that there MUST be a catch basin/soak away, or Yes the pipe can relieve the water pressure off the wall in its own right without the need for a catch basin/soak away.
Sorry to be a pain
Cheers
Richey
Posted: Fri Apr 04, 2008 11:29 pm
by Rich H
The perforated pipe needs to be laid to a gradient allowing water to flow along its length. At the end, the discharge needs to go somewhere, preferably a properly constructed soakaway.
I've also never built a retaining wall without a membrane.
Posted: Sat Apr 05, 2008 12:35 am
by lutonlagerlout
i have used membrane vertically when specified, but the point of a dpc in an out door wall baffles me??
what will it do?
LLL :;):
Posted: Sat Apr 05, 2008 6:30 am
by seanandruby
......weaken it at dpc level i would of thought :laugh:
Posted: Sun Apr 06, 2008 1:54 am
by lutonlagerlout
exactamundo sean!
LLL :;):
Posted: Sun Apr 06, 2008 9:05 am
by seanandruby
seen them pushed out and ready to topple with ground heave. got a photo of one somewhere i'll look it out.
Posted: Tue Apr 08, 2008 8:53 pm
by Richey
Thanks, that's much clearer. Will definately be using a membrane. Here's the tricky bit about building a soak away/catch basin at the end of the drainage pipe... the retaining wall will go right across the garden from fence to fence so there will be no room for a soak away at either end which means I'll have to bend the pipe round to either in front of the wall or behind it. Draining water away to behind the wall would be silly as surely the water would make its way towards the wall again?? Not to mention the depth of hole I would have to dig. That leaves digging a soak away in front of the wall. Fine, only I want a patio there. Is it ok to pave over a soakaway? Does any one have any thoughts on the best place to build this soakaway? (apart from into the neighbours garden)
Cheers Richey
Posted: Tue Apr 08, 2008 10:03 pm
by Rich H
Whoops - I typed without when I meant with. Damned double negatives.
Just to clarify.
Retaining wall = no dpc for me.