Tuff Form - Tile Advice

[Sandwich1987]

Hi guys had a little thread going in the Tilers forum asking for a it of advice on tanking the former with Kerdi, but Im happy that has now been solved. Got a it of another issue/query my bathroom is roughly 2.5m x 2m in an old 1906 tenement flat my joists are running along the longer wall of the room an are roughly at 400mm centres.

The issue I'm having is they are all un level from each other, because of this I decided to put down 25 wbp ply and pack under the ply until it was level. I've done this and now have the ply level in each direction and am happy with that. But when I sit my former on the ply is seems to sit flat on the outside edges but the centre isn't lying flat on the ply it's as if it's sprung up or the board has a twist or something in it? I was thinking about glue it down and using some weights to hold it down?

Any ideas?

 

[One Day]

Contact the supplying company? Wooden trays sound like trouble to me. Prone to moisture warping, expansion, contraction blah blah blah! also could be bent if you've stored it on its side rather than flat? just to rub salt in, i installed a wedi fundo tray last week. Absolutely perfect. The customer had bought a generic version for about a hundred quid less, but it was like a banana! You get what you pay for. Or if you've paid well, you should have a decent tray.

 

[Sandwich1987]

Sorry it's not a wooden tray it's grp should have mentioned that
It says in there installation instructions you can add additional screws on the surface to eliminate flexing but Seems to me it should lie pretty flat out the box?

 

[One Day]

Aah sorry. Mixing you up with someone else in here. Yes grp trays like impey can need a few extra screws to pull them flat. Just be sure to waterproof over any screw holes. It's part and parcel of those trays. Follow the instructions to the letter and you'll be covered if it fails.

 

[White Room]

A good video...View: https://www.youtube.com/watch?v=fck9lhts1Pw

 

[Dave]

Bang some screws in to pull it down and then membrane over for tanking...

 

[Sandwich1987]

I just did wht impish suggested and used a few screws and some pinkgrip seems to have done the job, will be covering with Kerdi so all good. Cheers

 

[One Day]

Be sure to lightly sand the surface and use kerdi-coll to fix the kerdi. Grp is notoriously problematic for adhesive.

 

[White Room]

Be sure to lightly sand the surface and use kerdi-coll to fix the kerdi. Grp is notoriously problematic for adhesive.

I used a spf, kerdi coll is super expensive.....

 

[One Day]

I used a spf, kerdi coll is super expensive.....

it sure is, but it don't half stick! Anything less than a 2 part adhesive then make sure it's a quality one!

 

[Sandwich1987]

I've bought some mapei Eco primgrip and was going to use a mapei adhesive like keraflex I'm sure I've read on here that should be ok?

 

[Old Mod]

I've bought some mapei Eco primgrip and was going to use a mapei adhesive like keraflex I'm sure I've read on here that should be ok?

£20 for Kerdi Coll now is a lot less than a few grand later on!

 

[Sandwich1987]

I've got kerdi coll, but the only reason I bought the ecoprim grip was on a recommendation from here.

 

[Old Mod]

Well if u have it, u should use it, best using Schluter adhesive with Schluter products.
Eco prime is a primer not adhesive.

 

[Sandwich1987]

Well I had bought it originally for the seams and joining my ditra to the kerdi on the former. I had been searching for advice on adhering the fleece to the former and even contacted both schulter and akw and neither would recommend an adhesive.

I had seen on a different forum someone recommended using kerdi fix and then later on using kerdi Coll but no one would confirm it.

So for this reason I went with what was recommended on here, and that was to sand the surface, prime the surface with the ecoprim and combine with a mapei adhesive. Are you saying this won't work?