cracks in cpi render external

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we seem to be getting alot of sagging cracks in our cpi render.turn up the day after application and there are dozens of cracks everywhere.getting pissed off with it now.topcoat is around 10mm thick.any thoughts?.cheers
 
Are you spraying your ribbons nice and tight so as not to trap any pockets of air whilst ruling?
 
Try a mist spray of water over render be for you leave and a light spatch or flat trowel . That should solve your problem .
 
I was thinking of changing my scratcher as this might help top sit on scratch better.cpi is laced with waterproofer so not sure if that is a reason as topcoat takes ages to pull in
 
I know it sounds obvious but why not put your top coat on thinner? 6-8mm, it might not sound much of a difference but it certainly makes plenty of difference on normal S&C.
 
Agree with Andy top coat should be thinner never had any cracking with cpi except in scratch coat due to
slumping which is not a
issue
 
Yes 10mm on a waterproof background is a lot for a render which is not a one coat render to start with. They make a one coat render now don,t they (CPI)?
 
Ok cheers.on next job I will spray scratch thicker to leave a thinner top coat.hopefully this will sort out the problem.does'nt look to clever floating in cracks the next day!!
Have you used CPI and webbers rigsby?which is the better product in your opinion?
 
bobby said:
Ok cheers.on next job I will spray scratch thicker to leave a thinner top coat.hopefully this will sort out the problem.does'nt look to clever floating in cracks the next day!!
Have you used CPI and webbers rigsby?which is the better product in your opinion?
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Never used CPI but I have used Webers OCR. From what I have read on here lately it looks like Weber is the better. I sprayed one recently though with ocr and in the thick areas of about 12mm I got a few cracks appear due to sag. I did a SAS Float last month and no such problems at about 8-10mm thick but unless it is like piss it is crap to spray but nice to rub up. Can take hours as well in the shade to go off.
 
Weber OCR is just over a pound or so more a bag but is light years ahead....and one coat on block. Bobby do you sponge the topcoat after float? It improves the finish IMO but more importantly closes in and hydrates the wall so it retains moisture better
 
I use CPI and OCR...depending on job, both have there places.

I use 10mm beads over scratch with CPI, make sure I get all my dubbing out done before.

Give the scratch a week to dry.

Top coat flat then sponge...never had a problem with cracking.
 
ithink spraying it too wet can be a problem too...... keep it thin and spray it a bit stiffer. and as said once finished try and give it a mist down. iv had a few hairline probs with cpi too. and i think im the only person alive that would disagree with everyone and say i dont like weber ocr....
 
I tried a sample bag of CPI general purpose render and it set hard and appeared to be waterproof. So for those that have used CPI GPR is it waterproof? If so anyone sprayed a top coat on and dashed it?

Weber ocr is not waterproof so no good for a dashing undercoat. Did a 15mm thick spray 2 days ago and managed to get it flat with a float finish but scoured because it was still wet a 4pm. 3c at night and next morning flatted with a trowel and it was so smooth a fly would have slid down it.
 
It has tons of waterproof in it rigs that's for sure.i would be careful how thick you put it on though as I found it to crack a lot if a little thick in places.not a lot of suction this time of year either so that would be good for dashing


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