Old scratch coat tough as old boots

[GBPLASTERING]

Good morning, the builder we are working for as gunned of the old pebble dash but the scratch coat will not move. So i was thing get them to wash it down get rid of the dust and muck. Then we can fix plastic beads SBR it then top coat with an 5-1-1 mix with render mix added. or could we use external pva instead of sbr. Thank you to anyone offering some advise.
:RpS_biggrin:

 

[Fatarm]

I've never used external pva,sbr slurry is good. Plasprime x. Has been mentioned also on the forum:RpS_thumbup:

 

[Arti]

What he said.............:RpS_thumbup:

 

[lizard821000]

i wouldnt use pva as a bonding agent outside, but mixed up with part water and used a sealing agent on loose/dusty surfaces is fine. if you want it to stick use sbr. a slurry is a bit OTT imo. sounds like you ll have plenty of key on the old scratch .

i hardly ever use sbr with my rendering as it can form to much of a barrier as appose to a keying/bonding agent i find,unless im going over painted surfaces which i also disc cutter key up, stuff tends to just sit on top of it, rather than soak in and key to whats underneath.

 

[nickelarse]

re scratch it over the top.

 

[GBPLASTERING]

i wouldnt use pva as a bonding agent outside, but mixed up with part water and used a sealing agent on loose/dusty surfaces is fine. if you want it to stick use sbr. a slurry is a bit OTT imo. sounds like you ll have plenty of key on the old scratch .

i hardly ever use sbr with my rendering as it can form to much of a barrier as appose to a keying/bonding agent i find,unless im going over painted surfaces which i also disc cutter key up, stuff tends to just sit on top of it, rather than soak in and key to whats underneath.

Hi am hoping to start this rendering tomorrow, so you are saying don't SBR slurry just paint neat SBR onto the old scratch coat. Will the new top coat sick ok without the slurry mix? and if I paint it on neat do you let dry first or should it be tacky like the slurry mix. Thanks

 

[Andy M]

Microgobetis will sort it

 

[GBPLASTERING]

Thanks for the replies on this topic. I went down SBR slurry mix in the end. Seemed to work well builder happy. Front on the house done. Rain forecast in Dorking tomorrow:RpS_thumbdn:. Just want to complete it before the real cold weather set in. Would of tried Microgobetis but couldn't find a supplier near me so my be try it next time. Thanks again Grant