Lobster wrote:
Stuart Noble wrote:
The Medway Handyman wrote:
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?

You can get waterproof PVA. AFAIK it only becomes waterproof when
mixed with cement as a slurry, but it might do the job.



All pva does is prevents the brickwork absorbing water from the mortar
before it's had a chance to set. Works indoors or out and really has
nothing to do with how waterproof it is in the long term.

Thanks both.

So does that mean "waterproof" PVA is snake-oil and I can just as well
use the ornnery stuff I already have in!?

David

IIRC exterior pva is called something else (eva?) and is more water
resistant but, as a sealer for masonry, it doesn't matter. It's only a
temporary barrier to allow the cement time to cure. Mortar sticks to a
shovel so well because the water doesn't get absorbed by the substrate.