On 13/03/15 23:14, Cursitor Doom wrote:
Hi all,

THe instructions for the shower base I'm installing say I need to add an
"anti-crumble" compound to the S&C mix. I can see how this would be
desirable since the shower base will be sitting directly on this bed of
mortar, but I've not come across such an additive before and don't recall
ever seeing such a thing, either. Is this just a fancy term for PVA or is
something more specific required?

SBR would be an extreme option.

But unless you wax/oil/sheet-with-clingfilm the underside of the tray,
do be aware that it will bond solid to the mix and will be impossible to
take off without a kango. I've used it in difficult situation and it
sets like iron.

I think for this application a drop of PVA would be sufficient - the
load is spread far and wide and I've not even heard of show tray beds
needing additives until now.