Advice on poor pointing of cobbles

[Benjseb]

Hi all

 

We’ve just had some landscapers in to sort our courtyard. About 1/3 of the cobbles had been lifted for some new drains so they had to be relaid and then it all repointed. 

 

We’d asked for this to be done in resin but the contractors decided it wasn’t feasible once on the job, due to the size of the gaps so did it in a concrete mix. 

 

 

They have now “finished” after working since May, but the quality of the finish is awful. Mortar on the face of the cobbles, raised edges, some has already lifted as it wasn’t dug out enough. 
 

So I need a bit of advice on how it can get fixed. Is there a way of solving this without digging it all out and starting again?

 

The contractors have tried power washing but it’s made little difference. They’re now suggesting grinding it but this worries me the cobbles will be damaged. 
 

We’ve only paid them for part of the job. What should our next steps be? 
 

Some pics attached. 

[Nickfromwales]

You could try a brick acid to see what is left in 'stubborn' cement, as acid should clean the residual cement of the faces of the cobbles at least and leave you with what remains. That will need to be scrubbed ( stiff broom if light residue or wire brush if heavy residue ) so approach your guy and ask for that  to be done before summarising.

If mortar ( the cement mix ) is already coming loose then it's not good news. At the very least these loose patches need 'raking' out and re-doing.

Edited July 31, 2020 by Nickfromwales

[Cpd]

Cement can cause serious damage some types Of porous stone, especially sandstone ... find out what stone you have and check it’s ok to have cement there....  The work looks terrible. If the sub bace was not compacted correctly then the whole lot is doomed to failure. You should be able to give the stones a good dunt with a rubber mallet and get no movement or sinking. I am not sure about how to resolve this but if it was me I would want the whole lot to come up, proper inspection of sub bace By someone in the know, you should be able to stamp down with your heal onto the prepared ground and get nearly no  imprint.   I think a layer of softer material is then laid into which the cobbles are driven down into and then sand and gravel fills the gaps. The problem with cement is that water can get in Between the cobbles and cement and then when it freezes there is no room for expansion and the cobbles can lift . it’s not my area of experience so maybe get yourself educated by doing a bit of research On line and phoning a few masons for A second opinion. 
 

 

[Benjseb]

Thank you

 

i think the sub ground was prepared properly as we saw them put in gravel, compact it down then add a very sandy mix of sand/cement. There didn’t seem to be much movement etc

 

i think the main issue is where there were existing cobbles and they haven’t dug out the dirt that was between them properly and just put a thin layer of mortar in

 

i spoke to them yesterday and their solution is to use a grinder with a diamond tipped “buffing” pad. One mention said it was on a pressure washer but not sure if I’ve misunderstood that. 
 

So apparently that will just remove the excess concrete. I’m concerned this will damage the cobbles and/or not fix the underlying issue of there being concrete which will just get pushEd out by weeds/frost?

 

They are supposed to be returning on Monday to tidy it up then want paying but I’m worrried we’ll be left having to repair it once winter arrives. 

[Cpd]

The diamond grinders are pretty brutal..... I wood be surprised if they don’t damage the cobbles. Not a lot more I can say but I think your going to have some ongoing issues. Best of luck. 

[Nickfromwales]

13 hours ago, Benjseb said:

They are supposed to be returning on Monday to tidy it up then want paying

Tell them you'll pay when you're happy and not a second before.