Rendering over masonry paint

[88v8]

Block wall, 60s. Sound cement render then old masonry paint.
Got a lot of the paint off, but can't get rid of all the mist coat.

Need to render over the render, to add 3/4" of thickness.
4:1:1 cement lime sand then 5:1:1

I think I should start with a bonding agent. SBR seems to be a favourite.
Which one would you use?

V8

 

[tell80]

sbr

 

[88v8]

Hehe, OK, any particular brand or are they all the same?

V8

 

[88v8]

I should take my specs when I go shopping... the small print, or considering the space taken up by the H&S crap, the tiny print.... when I got the SBR home, it says 'Do not use over painted surfaces'.
So I hired a needle scabbler and removed the rest of the paint. Not a job I'd want to do again.
Anyway, it leaves a good surface, no further prep.
Scratch looks OK.

 

[Deleted member 292770]

you could have used rendabond

 

[88v8]

you could have used rendabond

Thankyou.
I checked the data sheet of Bostik PVA (used to be Rendabond) and it says for outside work to use Bostik SBR, so I just bought some.
The first job went OK, but I have more to do with the same paint problem and I really don't want more days with the scabbler, so thankyou.

 

[Deleted member 292770]

my apologies. should have made myself clearer.
https://www.toolstation.com/everbui...VchoGAB3qLgipEAQYAyABEgIACPD_BwE&gclsrc=aw.ds
it’s rendagrip.
hope this helps.

 

[88v8]

my apologies. should have made myself clearer.
https://www.toolstation.com/everbui...VchoGAB3qLgipEAQYAyABEgIACPD_BwE&gclsrc=aw.ds
it’s rendagrip.
hope this helps.

Ahh yes, even better. I checked the data sheet and there is no problem over paint.
And I can wait until it's dried.
Bit cheaper at Sealants & Tools Direct https://www.sealantsandtoolsdirect....ip-extra-grip-render-bonding-coating-rendgp10
I'll still strip as much of the paint as I can, but this will make the job easier for an amateur like me
Thanks again.

 

[88v8]

Rendagrip yesterday, left a day to dry.
Scratch coat on this morning.
Very little suction.
Slow drying.
Waited two hours to scratch it.
Not sure how much grip it's got on the wall really. Feels strange with so little suction.
Will leave it until day after tomorrow to put the top coat on.

 

[Deleted member 292770]

It will be slow in this weather. and there wont be much suction given the rendagrip, paint ,and the wall will be damp to start with.
from my experience the stuff gives a good mechanical key so you should be fine.
the longer it takes to cure the better really as long as it don’t wash off overnight.

 

[88v8]

It will be OK if there's rain, it's under the overhang of the thatch.
Do you think two days is too soon for the top coat? Don't want to pull it off the wall when the top coat dries.

 

[Deleted member 292770]

i’d leave it longer . a week this time of year. but that’s just me.
2 days should be good.

 

[88v8]

I left it a week to do the second coat. No hollow spots when I tap it. Seems OK.
Second coat 5:1 as I said, but 4:1 for lime.