DIYbanter - View Single Post - Repairing powdery gash in external render

Stuart Noble

wrote:
On 12 Apr, 15:35, Lobster wrote:
A small lump of render has fallen out - think it's been knocked by
something. The hole is rather flaky and very powdery, so I think if I
just repair it as it using a bit of mortar, it will simply fall out again.

If this was an internal repair I'd be sloshing on dilute PVA first,
however that's not suitable for outside is it?

What does the panel reccomend I do?

Thanks
David

Dear David
PVA can re-emulsify
SBR is a glue and does not
Firstly cut out the render such as to make the hole larger next to the
brick that in is on the face of the render (undercut it like a dental
filling)
next put on undiluted SBR (Sryrene butadiene?) onto the brick and
undercut and within 30 mins whilst it is still tacky
put on the render with SBR in the mix according to the instructions
use a spllatter dash method of applying as best you can and leave it
to set before applying further coats of render
no coat should be more than say 12 mm thick
do not allow to dry only to set before applying the next coat
Chris

Why this obsession with SBR? Unless there's a damp problem, an initial
pva seal will be just fine. No need to mix it into the mortar either