Prepare surface after render ready to plaster

[chriselevate]

Hi,

I've plastered a few times and can do a good job (only my own house though). I sometimes dint know what to do about surface preparation before plastering.

Can you answer these two please?

1. Plastering over plaster that has been done several months ago and never been painted?
2. Plastering over a rendered surface that has been keyed and given 2 coats of PVA/water several months ago (ie it's dry now).

Thanks

 

[stevethespreader]

1, to replaster over new plaster would require 2 coats of pva the first one pref done the day before and the second one would be just before you skim and left to go tacky

2 plastering over render that has been already pva'de would require 1 coat of pva just before skimming and left to go tacky

 

[chriselevate]

Thanks for this and your quick reply. Really appreciate it.

When you say "left to go tacky" what consitancy are you mixing the PVA up with water?

And roughly how long are talking for it go tacky?

Does it mean that it doesn't fully dry so 10-20 mins? Or a lot longer?

Thanks

 

[NickB_99]

When you say "left to go tacky" what consitancy are you mixing the PVA up with water?

Ratio usually 5 parts water to 1 part PVA.
Sometimes I've gone for a bit thicker (4:1) if I think there might be problems e.g. going over some emulsion painted bits

And roughly how long are talking for it go tacky?

Start one corner of your wall where you would start plastering, work your way through and probably by the time you've done your plaster mix, where you started painting PVA mix will be tacky.
There's not a hard & fast rule.
If the surface is porous e.g. fresh plaster it can go tacky and even dry quickly. Ambient temperature will also effect it.
Like most things with plastering - experience helps a lot