rendering walls

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dcplastering

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Hi, could anyone please settle an issue regarding rendering.some plasterers add waterproofer in scratch coat,others in only there final coat,some in both coats I would be grateful if you could settle this argument thanks!
 
In theory if used properly it should be fine to use. I would never add to the top coat. It can cause problems with trapping in moisture. Also there is no need for finishing as it won't make any difference in the top coat only if its in the base coat as runs with malc says it will slow the suction of the top coat if used on the base.

I used to use half the recommended dose in the base coat just for a slight suction control element.

Remember it is easy to overdose on waterproofer and it can lead to disaster. It can separate the 2 coats in more ways than 1 and lead to the top sheeting off at some point.

If you can get away without using then don't use any is my advice
 
If you are talking about sand and cement render then I use a waterproofer in the base coat but not the top coat.

The base coat has a waterproofer to stop water penetration into the substrate and to give suction control on the top coat.

I do not put it into the top coat in case there is minor crazing or cracking. If water gets into the cracks and in between the two coats you can get seperation. As for water being absorbed into the top coat and consequent frost damage then the air entrainer (Febmix) collects the free running water in the air bubbles and takes up the expansion of water sono frost damage.

I used to in the 80's put water proofer in both coats before being advised about the above but had no problems and that work is still on today.
 
Im a wavey line man , when i see people who has done it all straight gets on my nerves lol theres more line when its like that , if you run a bit of string along a wavey one it would be quite abit longer
 
I've always scratched horizontally and straight. Never known of anything fall off/ delaminate/seperate. Never been called back to a job and never lost a wall due to too much/not enough water-proofer. Most jobs I do have water-proofer in both coats and I'd never known any different before joining the forum. ABSOLUTELY NO-ONE up here does a wavy scratch and we're in one of the most exposed areas of the country (Cumbrian coast). If I don't add water-proofer (Freeflo) I'll be using sand:cement:lime, the lime being a lime putty mixed at least 24 hours before applying to the wall :RpS_thumbup:
 
I do vertical lines. Occasionally wavy. And dont Waterproof either coat. Lots of lime in my scratch coat. Lots of cement in the top coat
 
bubbles65 said:
I've always scratched horizontally and straight. Never known of anything fall off/ delaminate/seperate. Never been called back to a job and never lost a wall due to too much/not enough water-proofer. Most jobs I do have water-proofer in both coats and I'd never known any different before joining the forum. ABSOLUTELY NO-ONE up here does a wavy scratch and we're in one of the most exposed areas of the country (Cumbrian coast). If I don't add water-proofer (Freeflo) I'll be using sand:cement:lime, the lime being a lime putty mixed at least 24 hours before applying to the wall :RpS_thumbup:
Click to expand...

if you have never done a wavy stratch you havent lived :RpS_wink:
 
bobby said:
b*ll***s
Click to expand...

Well there is more for the render to key too , if you measured every straight line on a wall ..... Then done a wall the same size and done the scratchs the same length apart but make it wavy the lines would add up to more than if they were straight
 
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