Is this key good enough on S&C

[Daveo82]

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???

 

[Daveo82]

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

 

[zolco]

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?

 

[Daveo82]

Did you had damp proofing done by any chance?

No mate an internal upstairs wall but they did add waterproof to the mix

 

[zolco]

No mate an internal upstairs wall but they did add waterproof to the mix

Not much key there that's for sure, just get the plasterer back who did it

 

[vfr12]

I'll be more worried about the bonding agent, if there is any + suction. Key could of been better tho.

 

[Marshy]

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

 

[Daveo82]

Not much key there that's for sure, just get the plasterer back who did it

They have said they will come back and blue grit it? Do you think the key is the cause?

 

[Marshy]

Sand and cement needs time to dry unlike modern lightweight backing coats before applying a finish coat

Sorry cure before the bigwigs give me any s**t

 

[Daveo82]

Sand and cement needs time to dry unlike modern lightweight backing coats before applying a finish coat

They left it about 4/5 days

 

[Daveo82]

I'll be more worried about the bonding agent, if there is any + suction. Key could of been better tho.

Bonding agent??? I think they just skinned straight onto S&C

 

[Marshy]

They left it about 4/5 days

Yes but if only the skim has "blown" they may not have brushed it down/damped down first or what was it rendered on to??

 

[vfr12]

Bonding agent??? I think they just skinned straight onto S&C

Good boys

 

[Daveo82]

Yes but if only the skim has "blown" they may not have brushed it down/damped down first or what was it rendered on to??

Rendered onto solid brick wall - they added metal mesh for extra strength

 

[Daveo82]

Good boys

Is that not the right way to do it???

 

[superspread]

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

 

[Daveo82]

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

They used thistle multi finish on top of S&C 2 coats - would bluegrit sort the key problem out?

 

[Marshy]

They used thistle multi finish on top of S&C 2 coats - would bluegrit sort the key problem out?

No

 

[Marshy]

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

 

[Daveo82]

No

Could it not be the key is not good enough - it was left to cute 4/5 days and there is no damp in the walls at all

 

[Lastlaff]

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.

 

[Marshy]

Could it not be the key is not good enough - it was left to cute 4/5 days and there is no damp in the walls at all

Unless they didn't devil float it etc or a "sandy" mix

 

[Marshy]

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.
View attachment 16518

I was taught to devil float in neat round circular motion and if my old lecturer could put an old 2 pence piece in your work with no "key" you got marked down

 

[Daveo82]

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.
View attachment 16518

It doesn't look like that - if I took all the skim off and painted with blue grit would that then be a good enough key to re skim

 

[zolco]

It doesn't look like that - if I took all the skim off and painted with blue grit would that then be a good enough key to re skim

You can only try

 

[beader]

I was taught to devil float in neat round circular motion and if my old lecturer could put an old 2 pence piece in your work with no "key" you got marked down

Figure 8's i was taught.

 

[Daveo82]

Figure 8's i was taught.

Would that key they've done not work then and cause the plaster to crack and blow

 

[spunky]

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

 

[Marshy]

Figure 8's i was taught.

Oh dear

 

[Daveo82]

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???

 

[Marshy]

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

 

[Marshy]

No one says f**k all but quick to comment on those that do you wankers

 

[Smudger1]

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 ?

 

[spunky]

Yes tap

Thanks mate so if I get all the skim off and blue grit it then reskim it could be ok???

yes

 

[spunky]

No one says f**k all but quick to comment on those that do you wankers

Ooh ooh sir me first