peterdewolf

OK lads, having a right mare here. Re-doing a bathroom, shower etc. Have boarded the shower with multipro and extended this board across to the end of the room. Existing crap was plywood which had rotted etc, didn't make sense to multipro the shower area then finish the wall with something different; just to keep everything kosher the entire wall, enclosure etc is the same material. 8X4 by 12mm multipro cementitious board. It's white, smooth on one side and slightly textured on the other. As per the 'destructions' I am tiling on the textured side.

Doing various tests etc and with a new bag of standard set wall and floor tile adhesive/cement. So about 30 hours ago I mixed a trial run on some scrap board and stuck a couple of clean subway tiles on, nicely notched etc.

Today I had a looksee, the cement had squeezed out a little and I tapped it gently with a trowel and it had hardened off beautifully but the tiles simply dropped off ! The cement had hardened and stuck firmly to the tiles but had ZERO adhesion to the board ! I remember Hardy board and I still have some of it, they used to say you didn't need to prime it and I never did, done many bit and bobs with it using tile cement and mortar etc, never had a problem.

What am I missing here, do I need to prime this ? I have some SBR, what dilution should I use ? It's a bit scary to get to this point and run up against a total failure of what I'd expect to be a simple job, sticking tiles onto cement board and expecting them to stay on.

I've got my foundations nearly dug out, about 3.5 x 3.5 m app 1 cubic m of concrete. I do have a small mixer. Going to be on my own with this and mixing it myself. I don't think I'll get the entire trench filled in one day ( I'm a bit crocked ) . Should I do it in two lengths, one today and the other tomorrow or fill the whole trench as far as I can do in a day and fill on top of the first pour the next day. Not ideal I know but I cannot get anyone to deliver to me, too small a load for them to bother.

Hello lads and lassies, Warrior is getting a bit bogged down and needs a few pointers