Is this key good enough on S&C

Daveo82

Member
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Hi recently had a room back to brick and S&C now a month later there are lots of cracks and hollow patches - when hacked off there are no cracks in S&C only skim is the key good enough? Any other reasons this could have happened???
 
View attachment 16511 Hi recently had a room back to brick and S&C now a month later there are lots of cracks and hollow patches - when hacked off there are no cracks in S&C only skim is the key good enough? Any other reasons this could have happened???
Also worth mentioning no cracks appeared for a good two weeks and when tapping the walls there were no hollow patches but as time has gone on (about a month now) they have appeared
 
Also worth mentioning no cracks appeared for a good two weeks and when tapping the walls there were no hollow patches but as time has gone on (about a month now) they have appeared
Did you had damp proofing done by any chance?
 
I'll be more worried about the bonding agent, if there is any + suction. Key could of been better tho.
 
View attachment 16511 Hi recently had a room back to brick and S&C now a month later there are lots of cracks and hollow patches - when hacked off there are no cracks in S&C only skim is the key good enough? Any other reasons this could have happened???
Sand and cement needs time to dry unlike modern lightweight backing coats before applying a finish coat
 
Looks like they've bonded or hardwalled it on top of the s&c? And the s&c is clean , no trace of plaster applied . Almost certainly lack of key
 
If the finish is "blowing " on top of a sand cement background it's either not dried/cured properly or there is an underlying issue letting moisture come through
 
Your S&C key should look like this - devilled up which not only flattens the S&C but also gives the finish something to 'grab' hold of.
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If the finish is "blowing " on top of a sand cement background it's either not dried/cured properly or there is an underlying issue letting moisture come through
I doubt it, if there was an underlying issue it wouldn't blow immediately especially if it were damp, it's not damp by looking at the picture and blue grit would provide a key
It's too little key and too thick skim
 
I doubt it, if there was an underlying issue it wouldn't blow immediately especially if it were damp, it's not damp by looking at the picture and blue grit would provide a key
It's too little key and too thick skim
Thanks mate so if I get all the skim off and blue grit it then reskim it could be ok???
 
I doubt it, if there was an underlying issue it wouldn't blow immediately especially if it were damp, it's not damp by looking at the picture and blue grit would provide a key
It's too little key and too thick skim
I f**k**g give up
 
I'dstrip skim off if easy and get small masonry nails and see if soft enough to devil float it up to try and get a bit of key knit then PVA water mix on it skim when tacky ?
 
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