How to prep for a top coat help

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mrsmith

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Hi there,

I have applied a scratch coat on an exterior wall yesterday over two coats of exterior PVA. The scratch coat was 4/1 mix and all went well and it is drying nicely.

Now I might have made a boo boo as I did not add any waterproofer to the scratch coat??

What is the best way to finish off my top coat?

1. Thoroughly wet scratch coat and apply another 4/1 without anything added?
2. Two coats of PVA and apply another 4/1 without anything added?
3. Thoroughly wet scratch coat and apply another 4/1 with a waterproofer added?
4. Just throw another mix on and stop worrying about it?

Its a 1m x 2m repair and a 0.2m by 6m repair on old brickwork.

Any help would be much appreciated
 
Look mate if it was me I would have put the base on seen what suction was there and doubled up same day for a small area as that.
 
henry said:
Look mate if it was me I would have put the base on seen what suction was there and doubled up same day for a small area as that.
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Thanks for your prompt reply. I am a complete newbie to any type of rendering so I am sure there are many better ways I could have done it. If you had been watching me get to grips with my first coat you probably would have been shaking your head or in fits of laughter :-)

What would you do now I am in this situation though?
 
Not sure the tecnical term but smooth I suppose. I will finish using a plastic float.

The top coat will be about 5-8mm
 
So long as the scratch coat has dried out you could always pva it again and while it is tacky put your top coat on. Do it early in the day it could take hours to go off although this week it's going to warm up. Pva the edges to your patches as well. Dont play with it or it will slump and you will get your self in a pickle.
 
Is the 0.2m by 6m patch from a vertical crack or something? If so, you probably should have put some expanding metal lathe on it first or the crack might re-appear. Anyhow if you top coat that one first you will be able to control it as you go along and have a good idea of the suction for the larger patch:RpS_thumbup:
 
Rigsby said:
So long as the scratch coat has dried out you could always pva it again and while it is tacky put your top coat on. Do it early in the day it could take hours to go off although this week it's going to warm up. Pva the edges to your patches as well. Dont play with it or it will slump and you will get your self in a pickle.
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Thanks for the advice. It looked dry enough and there is an escape route at the edge of my beading for moisture should a little be left.

I gave one coat of PVA the night before last and tried it in the morning and no suction. So gave it another coat so as to apply to a tacky base and it went on fine!
 
bubbles65 said:
Is the 0.2m by 6m patch from a vertical crack or something? If so, you probably should have put some expanding metal lathe on it first or the crack might re-appear. Anyhow if you top coat that one first you will be able to control it as you go along and have a good idea of the suction for the larger patch:RpS_thumbup:
Click to expand...

I know its a weird shape. I have cut the first couple of feet of blown cement render on my old 1850's terrace to re coat in Lime render. The house is on a slope and the section that keeps blowing has soil inside it so moisture could not escape.

Just my luck its super hot! I am spraying a fine mist on my lime scratch coat and it is covered in tarp to protect from the sun. I plant to top coat in 5 days.

Any other lime render tips for applying my top coat?

Quite impressed with my first ever render repair the cement top coat looks pretty good.... for an amature.

thanks again for your hep guys
 
Simplybest on here has done a fair size lime render job in recent years. I think if you rush it by putting to much on at once or not letting it dry between coats it will crack. A bit like Limelite renovating plaster.
 
Just an observation, your first post indicated forgetting to use waterproofer, this actually will have no effect in a lime mortar other than offering ease of use through air entrainment. Waterproofers need to bind with the cement molocules to create a waterproof render.

Your best way of controlling suction is through copious amounts of water, then applying top coat once surface water is not visible( otherwise it will act as a slip plane and your mortar will be on the floor before you know it)

Are you using an hyrdraulic lime , or a non hydraulic lime putty !!!
 
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