PVA & GRANO DUST TECHNIQUE?

[Ruggers]

I had a plasterer round to quote for some external rendering to an existing scratch coat. But they suggested adding PVA & grano dust wet dash mix to the wall before they rendered it as it didn't have much to adhere to.

What is the method for this and once applied do you just add your finish sand and cement render?

 

[Alastairreid]

I wouldnt use pva....SBR would be better.

 

[stevethespreader]

I wouldnt use pva....SBR would be better.

agree with al alsoI've never heard of grano dust being used its a first for me

 

[Micilin]

SBR and OPC with it will make a very good key. Presuming brushed on or scudded (Harled)?

Sharp sand (6mm down) is cheaper but even using rendering sand is okay.

Good shout by Alastair- never use PVA outside.

 

[Ruggers]

Thanks guys, grano dust was just what was suggested, I heard the same years ago too from another plasterer. Not even sure what it is normally used for. I think he just suggested painting it on like you say or flicking it on like a slurry/wet dash style as he said it was messy.

If sharp sand will be better I could use this.
I didn't realise there was much difference with PVA and SBR. I have a large bottle of Sovereign SBR from a tanking job I could use.

 

[Ruggers]

What is OPC?

Also once I've applied this SBR mixture can the finish coat go onto this or will it need another scratch coat?

 

[JohnD]

ordinary Portland cement



PVA is not waterproof and will turn to slime outdoors (there is a waterproof version)

 

[Alastairreid]

What is OPC?

Also once I've applied this SBR mixture can the finish coat go onto this or will it need another scratch coat?

Scratchcoat then your finish.

 

[stevethespreader]

ordinary Portland cement



PVA is not waterproof and will turn to slime outdoors (there is a waterproof version)

waterproof PVA is only waterproof when used as an Admix http://www.amazon.co.uk/gp/aw/d/B00...iption_secondary_view_pageState_1414602341751

 

[Ruggers]

Alastair - I have a bare block wall that I have scratch coated but didn't comb it with a decent comb and just used a trowel so there isn't a decent amount of grooves for the finish coat. It has waterproofer and a good hold but the lack of comb marks is the problem so that's why I decided to add the SBR and sand/grano mix to it.

So do I still need to re apply a scratch coat to the grano dust then a finish coat on top of that or can I just add the finish coat to the sbr/grano?

Just need to know before I start as this might build it out quite a lot and wondered if it was better to chip off the first scractch coat instead which could also be a hassle.

 

[Alastairreid]

Oh i see,

Sorry dan i just re-read your original post.

carry on with your finishing coat now.

 

[Ruggers]

Hi finally got some time to get the grano dust & sharp sand/SBR mix on but before i do, if there any certain way recommended, I was going to mix it up in a bucket neat, into a thick slurry and just paint it on with a large brush or flick it on with a trowel of some sort?

Whats best?

 

[Ruggers]

brush it on with a multi task block brush or flick it on like wet dash anyone?