SBR or PVA

[J123]

Hi......i need advice on how to fill in missing plaster behind old skirting.
I am going to stick board to it afterwards. Do i PVA or SBR the wall first then fill with cement or bonding?
Thanks
John

 

[noseall]

PVA

 

[J123]

Thanks noseall........

 

[^woody^]

Neither.

Beleive it or not, Onecoat or bonding is designed to stick to walls.

 

[J123]

Thanks woody, does carlite bonding stick to the old black mortar and the old plaster above the gap?

 

[^woody^]

Bonding seems to stick to anything! Just scrape all the loose stuff off, brush away any dust, and brush or spray a bit of water on first.

If plastering over plaster, then make sure the existing plaster is sound.

 

[J123]

Thanks woody

 

[noseall]

PVA (as well as water) will help control the suction/shrinkage and give a wee bit more working time. Be aware though, once you add water to bonding, you are on the clock. When it goes - it goes rapidly. So make sure you are prepped and have some clean water ready to wash the tools and the mixing bucket etc.

 

[opps]

I am a decorator, rather than a plasterer. I often see hairline cracks where new bonding meets old plaster. For that reason I would recommend PVA rather than just wetting the old plaster.

I tend to use SBR in situations where I don't want the water in adhesives to soak in to the the substrate, eg when tiling over plaster. PVA is often used but the water in the adhesives (or leaks) can reactivate the PVA and result in the tiles blowing or falling off. Additionally when doing exterior masonry repairs, SBR is preferable.

 

[^woody^]

I often see hairline cracks where new bonding meets old plaster. For that reason I would recommend PVA rather than just wetting the old plaster.

I am going to stick board to it afterwards

 

[opps]

Good point but there are likely to sections where the bonding required will not be hidden by the skirting.