Hi everyone :) Skim and render hairline cracks

#1
Hi everyone :) I'm new here...I'll cut to the chase...I've been having a problem for many years. I apply waterproof render to a wall brick wall. 3 sand, 1 cement with sika 1 in scratch coat. Top coat same mix without sika. Let this dry out and apply skim. Skim always hairline cracks...Any thoughts or tips please?
 
#3
Is there any movement of the building ?
If not, only thing can think of is bad plaster.
 
#7
Thanks for the feedback guys...Let me throw in a little more background. I work for a damp proofing company. The specs set out for waterproof render for damp proofing is 3:1. Over the years I've used a waterproof scratch and top coat and then moved in to using waterproof scratch an non waterproof top coat.
In both cases the skim hairline cracks and the render also hairline cracks in some cases. Using a weaker waterproof mix will not serve to do it's job and the damp will push through...Are there any damp proofing plasterers/ specialists who have any advice...
 

Dropsalot

Private Member
#8
Spend time fixing the reason the wall is damp in the first place. Remove the source of water and you will not need waterproof render.
 
#9
Thanks for the feedback guys...Let me throw in a little more background. I work for a damp proofing company. The specs set out for waterproof render for damp proofing is 3:1. Over the years I've used a waterproof scratch and top coat and then moved in to using waterproof scratch an non waterproof top coat.
In both cases the skim hairline cracks and the render also hairline cracks in some cases. Using a weaker waterproof mix will not serve to do it's job and the damp will push through...Are there any damp proofing plasterers/ specialists who have any advice...
How long are you leaving the render before you skim it? Needs to be minimum 24 hours.
4-1 is fine for damp proofing with waterproofer in both coats
 
#10
How long are you leaving the render before you skim it? Needs to be minimum 24 hours.
4-1 is fine for damp proofing with waterproofer in both coats
Thanks for the reply.
Usually leaving the render at least 24 hours before skimming. Why is a stronger mix prone to cracking? And why does the drying time make the difference? I'm not questioning your pointers but interested in the science behind them.
 
#11
Thanks for the reply.
Usually leaving the render at least 24 hours before skimming. Why is a stronger mix prone to cracking? And why does the drying time make the difference? I'm not questioning your pointers but interested in the science behind them.
The drying time is to do with shrinkage, not sure why a richer mix is more prone to cracking to be honest
 
#12
Hi everyone :) I'm new here...I'll cut to the chase...I've been having a problem for many years. I apply waterproof render to a wall brick wall. 3 sand, 1 cement with sika 1 in scratch coat. Top coat same mix without sika. Let this dry out and apply skim. Skim always hairline cracks...Any thoughts or tips please?
your 3to 1 is that measuerd in buckets or shovels big difference
 
#13
Thanks for the feedback guys...Let me throw in a little more background. I work for a damp proofing company. The specs set out for waterproof render for damp proofing is 3:1. Over the years I've used a waterproof scratch and top coat and then moved in to using waterproof scratch an non waterproof top coat.
In both cases the skim hairline cracks and the render also hairline cracks in some cases. Using a weaker waterproof mix will not serve to do it's job and the damp will push through...Are there any damp proofing plasterers/ specialists who have any advice...
 

Cockney1

Well-Known Member
#14
Hi everyone :) I'm new here...I'll cut to the chase...I've been having a problem for many years. I apply waterproof render to a wall brick wall. 3 sand, 1 cement with sika 1 in scratch coat. Top coat same mix without sika. Let this dry out and apply skim. Skim always hairline cracks...Any thoughts or tips please?
You haven’t got a fuckin clue what you’re talking about and by the sounds of things you are a complete wally!!
Cheers!
 

lurpak

Well-Known Member
#18
FOOK ya hairline cracks. bigbish about to take on bacon in other thread massive showdown f**k sakeeeeeeeeeeeeeeeeeeeeeeeeeeeee get on it
 
#26
Hi everyone :) I'm new here...I'll cut to the chase...I've been having a problem for many years. I apply waterproof render to a wall brick wall. 3 sand, 1 cement with sika 1 in scratch coat. Top coat same mix without sika. Let this dry out and apply skim. Skim always hairline cracks...Any thoughts or tips please?
Welcome along