More crazing

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solway

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In ye're opinion why has this crazing happened. Napped finish about 2 years ago
 

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Can happened for any number or reasons i.e dried too fast, too much water in the mix, scratch coat stronger than finish coat,too much clay/silt in your sand
 
Hi Jamesdooley. isn't the scratch coat meant to be stronger than the finish coat. Napped in late November and scratched in October. Finish mix was 25 shovels sand to 4 shovels cement to 1.5 shovels lime and 150ml waterproofed...... Definitely didn't dry too fast. It was in by 9am and napping for 2pm. Wet down prior to coating aswell. I see this alot lately and I'm beginning to think it might be waterproofer reacting with the lime...or else dirty sand
 
Hi Jamesdooley. isn't the scratch coat meant to be stronger than the finish coat. Napped in late November and scratched in October. Finish mix was 25 shovels sand to 4 shovels cement to 1.5 shovels lime and 150ml waterproofed...... Definitely didn't dry too fast. It was in by 9am and napping for 2pm. Wet down prior to coating aswell. I see this alot lately and I'm beginning to think it might be waterproofer reacting with the lime...or else dirty sand
Sorry mate I ment finish stronger than the scratch,
Hi Jamesdooley. isn't the scratch coat meant to be stronger than the finish coat. Napped in late November and scratched in October. Finish mix was 25 shovels sand to 4 shovels cement to 1.5 shovels lime and 150ml waterproofed...... Definitely didn't dry too fast. It was in by 9am and napping for 2pm. Wet down prior to coating aswell. I see this alot lately and I'm beginning to think it might be waterproofer reacting with the lime...or else dirty sand
sorry mate I ment finish stronger than the scratch coat, might be an idea to check your sand supply, can always do a simple field test to check for silt, put a sample of your sand in a clean jar, add a solution of teaspoons of salt and a litre of cold tap water, close the lid shake it up and leave for about half hour or so,if the layer of silt that settles on top is more than 1/10 the size of the sample , it has a high fines content so it will take more mixing water which will result in shrinkage, I haven’t used waterproofing in sand/cement since leaving Ireland bout 11years ago so not sure if that’s your problem to be honest
 
Sorry mate I ment finish stronger than the scratch,

sorry mate I ment finish stronger than the scratch coat, might be an idea to check your sand supply, can always do a simple field test to check for silt, put a sample of your sand in a clean jar, add a solution of teaspoons of salt and a litre of cold tap water, close the lid shake it up and leave for about half hour or so,if the layer of silt that settles on top is more than 1/10 the size of the sample , it has a high fines content so it will take more mixing water which will result in shrinkage, I haven’t used waterproofing in sand/cement since leaving Ireland bout 11years ago so not sure if that’s your problem to be honest

No
 
I was wondering if that was due to scratch coat being too strong, as an outfit that mixed 2bags to 25shovels seems to happen them a lot, usually mix 2bags to 32shovels. Thought maybe their scratch coat was that strong any movement caused the undercoat to split. But it was only an idea, no idea why tbh.
 
Just to say we must have 10-12 house's done last year with the exact same mixes for each house. I'd say of the 10-12 houses done iv seen this sort of crazing in maybe 3 of them. We usually scud and scratch with whatever sand is left from the blocklayers and order more when it's needed. I'd give the client 3/4 suppliers to get a plastering sand delivered from.
 
Just to say we must have 10-12 house's done last year with the exact same mixes for each house. I'd say of the 10-12 houses done iv seen this sort of crazing in maybe 3 of them. We usually scud and scratch with whatever sand is left from the blocklayers and order more when it's needed. I'd give the client 3/4 suppliers to get a plastering sand delivered from.
Do you d spatter coat before the scratch?
 
We do a scudding coat at 2 to 1 on every project. It's religion. We use a standard shovel. I have buckets that we use for gauging out and they hold 4 heaped shovels of sand well compacted and hold just under a full nag of 25kg cement (opc). I'm fierce particular when mixing and gauge to the the,down to the ml of plaz/w'proofer. Pisses me off when s**t like this happens....
 
It looks to me like it’s just drying to quick, could be down to suction even though there’s waterproof in it, sun on the walls or wind, to be honest if you troweled it up good enough when painted it shouldn’t show
 
I'd doubt drying too quick. There was no panic with it all day and its in the middle of a wood so well protected...and napped late November so damp coolish weather around then plus it was wet down the evening before and the following morning prior to laying on.....
Probably be fine when painted but it might not me painted for a couple of years...
 
That type of cracking is caused mainly by quick drying or significant temperature difference between the scratch and top coat, which causes movement. You need to go back and think which one is it.
 
Just to say we must have 10-12 house's done last year with the exact same mixes for each house. I'd say of the 10-12 houses done iv seen this sort of crazing in maybe 3 of them. We usually scud and scratch with whatever sand is left from the blocklayers and order more when it's needed. I'd give the client 3/4 suppliers to get a plastering sand delivered from.

i don't like the idea of using block layers sand to soft. a lot of plastering sand is to soft as well.
sand is of different quality from each quarry. we know our local quarries and pick the sand up our selves.
 
Was out for dinner Sunday at a restaurant we plastered 18 months ago. Sponged finished elevations on this place up on 80m2. Used the same mix as the house in this thread and the restaurant is fine. It was after raining aswell so crazing should have been evident..... 1 thing I didn't mention was that the owner of the house was drawing water in 5 gallon drums(about 15 of them) and keeping the 200gl water tank topped up. Water seemed to be OK to look at.....although we never tasted it.
VFR12 you mention significant temperature change. What do you mean by this. Temp change to frost or temp change to heat wave?
 
Was out for dinner Sunday at a restaurant we plastered 18 months ago. Sponged finished elevations on this place up on 80m2. Used the same mix as the house in this thread and the restaurant is fine. It was after raining aswell so crazing should have been evident..... 1 thing I didn't mention was that the owner of the house was drawing water in 5 gallon drums(about 15 of them) and keeping the 200gl water tank topped up. Water seemed to be OK to look at.....although we never tasted it.
VFR12 you mention significant temperature change. What do you mean by this. Temp change to frost or temp change to heat wave?
Yes, it can work both ways. I have mentioned before that controlling suction is at the base of our trade. Not only drying quick, but too slow as well. Reading your post I assume it has gone the other way for you. If you say same mix, same method etc then you exclude the mix from the problem . What I think happened in this case is you hit the wall too earlier and caused dragging, respectfully friction between the two coats. If is too soft you don’t touch the top coat, leave it till bonds to the scratch and sets to be ready for sponge or float. I always compress the render with float to minimise this problem exactly. The difference between summer and winter cracking is the size, but I’ll leave that for another day;)
Hope that helps
 
Cheers vfr12 but nah,it was fine to float(twice) and napped up OK. The plinth probably was a bit "soppy" due to it being layed on because after rulling off we had a barrow left over. Would frost create this effect....trying to remember if the nights were around freezing temps when done...
 
Cheers vfr12 but nah,it was fine to float(twice) and napped up OK. The plinth probably was a bit "soppy" due to it being layed on because after rulling off we had a barrow left over. Would frost create this effect....trying to remember if the nights were around freezing temps when done...
Running out of ideas so ..... f**k off! :fuckyou:
 
I rendered a house in December, mixed everything same as usual, only difference I used frostproofer in the mix, it had crazed to the extreme, when damp after rainfall but cracks not visible when dry. Thing is the client is blaming me. Although he told me at the time that he was going to paint the house this summer, he now seems to think the paint won’t hide the crazing
 
I rendered a house in December, mixed everything same as usual, only difference I used frostproofer in the mix, it had crazed to the extreme, when damp after rainfall but cracks not visible when dry. Thing is the client is blaming me. Although he told me at the time that he was going to paint the house this summer, he now seems to think the paint won’t hide the crazing

Het him to paint it and see.... or offer to paint it....
 
Het him to paint it and see.... or offer to paint it....
The only problem would be if the crazing showed through the paint where would I be? I don’t think it will though as I see lots of crazing in unpainted render, and none in painted. Probably the best option for him would be acrylic it
 
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