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Posted: Fri Sep 26, 2014 9:59 am
by DNgroundworks
Hi all, got a problem 
Question in construction detail, prompted by LLL's pictures of his wall on the recent work thread.
Built a few retaining walls a couple of years ago for an elderly lady. Anyhow the damn things, 3 in total all separate to each other have started to move.
Upon inspection, it turns out that the backing block have gone very soft and in some places turned to dust.
LLL, i see your wall is 300mm thick ish, at about 900 high?
The detail of ours is, 200mm reinforced concrete footing, 140mm 7n concrete block, 60mm gap filled with lean mix, 90/100mm staff blues facing brick, all tied together. So 300mm thick. Drainage etc all there.
The wall/walls is around 900mm high at the highest, standing up around 150mm proud of the lawns behind them?
Good stable ground, readymix concrete on decent clay etc the drystone walls that where replaced by the brick walls had been there 20 years and hadnt moved, albeit they looked naff.
Does that sound ok? And has anyone seen concrete blocks do that? I have a video somewhere of me crumbling a block with one hand!
Posted: Fri Sep 26, 2014 9:42 pm
by lutonlagerlout
if it crumbles dan its likely to be a clinker block not concrete
concrete blocks just dont crumble
have you got a picture
chances are there is bad ground around and the footing has moved
cheers LLL
Posted: Fri Sep 26, 2014 9:50 pm
by dig dug dan
Weepholes present and correct?
Posted: Sat Sep 27, 2014 7:18 pm
by GB_Groundworks
How wide was the footing general rule is 2/3 rds the height
Was it a designed wall by engineer or just your spec?
Posted: Mon Sep 29, 2014 8:48 pm
by DNgroundworks
Not clinker Tony, solid concrete, well so it said on the invoice anyway. I built the backing structure and got a team of brickies to face it up, i know they werent clinker i can remember how heavy they where! But they do look like those lightweight block i must admit but they aint. The manufacturers rep said that doesnt matter, as they are both 7n in strength anyhow.
Yes Dan, but i see no point imo, not when there is a 100mm land drain and full fill of shingle behind the wall.
From memory Giles i reckon its 500mm wide. Not designed by an engineer.
Thing is if there where no weep holes, no drain, crap footing.....the blocks should still not disintegrate, i mean there in foundations country wide, submerged in damp ground forever?
Posted: Mon Sep 29, 2014 9:38 pm
by Brucieboy
Have you questioned the manufacturers rep as to why he thinks the blocks have disintegrated?
Posted: Wed Oct 01, 2014 4:30 pm
by DNgroundworks
I did, and he didnt have an answer he basically said, it doesnt really matter which type of block it was they are supposed to be the same strength and then he said its very strange. He took a sample for analysis.
Posted: Wed Oct 01, 2014 6:38 pm
by gonchy
i remmember a block of flats we were doing the roof on back in late 2011 i think when we started joistins some of the blocks started to crumble they were hard on the outside but hadnt cured inside anyway cut a long story short the bricklayers had to check every block in building ended up changing 6 pallets worth of block through out the whole builing
maybe somthing similar
Posted: Wed Oct 22, 2014 8:10 pm
by DNgroundworks
Had a mush out today from aggregate industries, came all the way from sussex to collect samples.
He reckons it either suphate attack or carbonated water attack (carbolic acid) from the surrounding soil.
Which i reckon is complete rubbish....the blocks have gone nackered but the mortar joints and concrete commons within the wall havent.
It goes on!
Posted: Wed Oct 22, 2014 9:22 pm
by lutonlagerlout
sounds like total bollox
sulphates can attack cement but are unlikely to attack concret blocks
from what you have said it sounds like the blocks arent right
LLL
Posted: Thu Oct 23, 2014 1:40 pm
by DNgroundworks
I think so to Tone.
The thing that scuppered him was some other blocks that at the beginning of the job i brought around 100 or so from the last job and used them up in the first part of the wall and they are as hard as when they went in and the wall hasnt moved at all there.
I cant find much on the net about this carbonated water produced by the grass!
Chances of them paying for repairs?
Posted: Thu Oct 23, 2014 6:28 pm
by lutonlagerlout
they will drag it out as long as possible
if you get an independant report they may be stuffed
chances are you wont be the only person with a knackered wall
LLL
Posted: Tue May 12, 2015 9:36 pm
by DNgroundworks
Just thought id update this, the manufacturers paid out, sorted!
Posted: Tue May 12, 2015 9:46 pm
by mickg
that's a good result Dan
Posted: Thu May 14, 2015 5:31 pm
by DNgroundworks
Aye, i was over the moon to get the offer from them, more so in fact for the elderly lady whos house it was.
Took some persistence though, around 6 site meeting and 18 months of to'ing and fro'ing!