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
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.
There are deffo two different grades, the waterproof one being twice the price of the standard.
You buy at wrong place.
General purpose - £3-00 Water resistant - £3-12
Both per Kg inc. vat. Seems to be decent qaulity - least I have never had a problem with it, conforms to all sorts of BS and Euro standards.
Or I do! Difference, though, is negligible.
As I was writing I realised that it actually says "water resistant" not "waterproof". I guess it depends on quite how important your application whether the difference might be significant.
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
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