Advice needed on badly finished wall.

[brarm321]

I wonder if some of you could give me some advice. I’ve just had my garden landscaped and some retaining walls built. They were rendered (scratch coat then 1 finish coat with stuff they mixed up themselves) about a month ago and in the mean time 2 sections of wall have developed a lot of mainly vertical hairline cracks, also a patch about 20cm sq has blown. I'm pretty sure the wall hasn't moved (it's hollow block filled with reinforced concrete). We had it decorated the other day and the guys chased out the cracks and filled them and also knocked off the blown render and patched it up. The trouble is it looks like a dog’s dinner now. The patched section has a completely different texture and the filling looks terrible. The filler used was toupret murex and they are saying it's too hard to rub down properly, I had a go myself and it is pretty tough but even if it is rubbed down enough it's a different texture to the rest of the render so still shows.
Just wondering what the best option is to sort it out. I’ve been reading the forums and see there is this thin coat stuff – would that be suitable to just go over the top of it all or does it require the whole system to be used (i.e. the mesh and scratch coat)? If just the thin coat is suitable would it require new beading at the external angles or is it so thin that it wouldn’t matter? Worst case I suppose is that they have to knock it all off and start again.
Any advice would be really appreciated.

Cheers, Matt

I've attached a few pics to give an idea of the problem.

 

[theclemo]

take it off.

 

[jackom]

as clemo says needs to come of

 

[DannyMac]

Have the back of the walls been tanked?

 

[brarm321]

Thanks for the advice so far. Yup the back of the walls were tanked with plastic sheeting and the face was painted with dpm liquid.

 

[bubbles65]

are they 4 inch walls?

 

[malc]

it looks to me that there is no expanision joints in the blockwork and these are thermal cracking.

 

[FreeD]

Walls don't look wide enough to be retaining. Water could be getting in from above, whack some copings on. Could be coming from behind. Any expansion joints in blockwork (if required)?

Pretty much every wall I've seen which is rendered on top is f**ked after a couple of winters.

Don't bother with the thin coat until you have sorted the source of the cracking.

I wouldn't bother rendering retaining walls they always crack.

Was this a pay less pay twice job?

 

[brarm321]

The walls are built with 210mm wide hollow concrete blocks, have steel reinforcing bar running up them and have been filled with mortar. The back of the wall is tanked with waterproof membrane and also has compressible polystrene panels to protect against swelling of the soil, there is also a load of drainage behind the wall. The long wall in the picture which is the main problem is 9m long and doesn't have any expansion joints. It certainly wasn't a pay less job and to be fair the rest of it has been done to a great standard it just seems the contractors used to render and decorate have let the side down. They told me the cracks were due to the weather as the rendering was done in those rare dry days in between the rain last month when it was also quite hot and windy. The patch that had blown was only the finish coat and I could see that a crack which ran down through that section only went a small way into the finish coat and not into the scratch coat beneath.

Thanks again for all of the help so far. If I get them to knock it off and start again is there a particular type of render which would be less likely to crack? I've seen there's products like StoRend which claim to be much more crack resistant.

 

[malc]

i still think that this is thermal cracking.
i would contact the manufactor of the concrete pots [blocks]. i am sure they will answer that 9m in lenth is to much with out an expansion joint.
i would have filled the pot with concrete not mortar i think this is a design fault, not the plastering

 

[brarm321]

Thanks Malc, if it is thermal cracking can an expansion joint be put in now and would crack resistant render be better able to cope?

 

[DannyMac]

Wouldn't an expansion joint in this type of retaining wall weaken it?

 

[jackom]

Imo if you get them to hack of re scratch, allow it to dry and give it a drink every couple of days it will be fine, seems like dried out to fast as it sounds like everything else has been done correctly then the render has been rushed