We had new 30m long by 1m high natural stone wall and steps built in the garden last autumn. The wall is made from blocks of various sizes with sandstone coping stones and treads. It's a retaining wall but we used the original retaining wall as the back support and then filled between the two with cement.
On the days we built, the temperature was at least 10-12 degrees, but there were a couple of nights where it fell below 5 degrees.
The builders at the time assured us that this would have no effect on how the cement set. Having waited six months to get someone to actually build the wall we went ahead, knowing the next window might not be until spring.
Now, we have found that virtually none of the coping stones or treads have set. They can be lifted off in your hand which is of course dangerous. The builders have agreed to come back to rectify the work but have suggested that we use an adhesive to fix the stones back on rather than cement this time. I have never heard of this and have two questions that I wanted to ask those who might know better than myself:
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have you ever used a brick or stone adhesive for this kind of purpose, how long does it last and how strong is it? Would you recommend it or should we ask the builders to take all the cement of the top layer of stones and start again?
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what should we be looking for in the rest of the wall? Could the same problem have compromised the safety of the structure and where would we find weak spots?
Thanks in advance for any help, sorry for the long post!!