newbie tiller alert!! help!!!

[goodjay]

hello all.
i have a dilema?
ive just tilled my bathroom (which looks great) and i now have to do the floor.
the floor has a concrete base (perpose built flat) with a couple of inches of polystyrine and then 18mm floor boards (not slats) floating ontop of it.
it was sterdy enough untill i had to cut a slice of it up to adjust some plumbing from an old rad in order to fit a towel rail.
this was when i discovered the boards were just floating ontop of the poly.
so now ive cut a new peice of board to fit inplace of the old one, the floor has lost its rigidness a little bit. ive had to screw the new board through the ploy and into the concrete floor because it was sitting loose ontop of the poly.
but to get a decent hold it now sits a couple of mm lower than the reast of the floor. but atleast its more solid now.
however the existing floor which meets the new floor now has a bounce on it because thats where it has been cut.
the bounce isnt major but enough for me to think twice before tiling!
im using Ditra and was just wondering if i could just build up the 2mm descrepency with adheisive so its all level again and that the small amount of bounce will be lost once the Ditra and slate tiles are down.
its only about 2.5sqm and the tiles are 30x30.
any info would be good guys as im sitting here twidling my thumbs thinking what to do and its bank holiday and i want to get this floor down so i can go down the pub!!
cheers, Jay.

can take a pic if it helps?

[Dave]

Hello Jay and welcome......


Thats a floating floor Jay.........Not a very good idea to tile it IMO....

A very high risk of tiles debonding , even with ditra installed....

Ditra is only for lateral expansion and not deflection.....

If you were to screw and plug the whole floor then that could work but then you have to be aware that you could puncture the DPM...

[goodjay]

hello Dave.
so what would you suggest then mate?
take it all up and fix some 3/4in ply down then Ditra then tile?
was kinda hoping someone was going to say "yeah all good mate go for it!" lol
or could i not ply over the existing floor? was hoping not too to save planing the door and have a high floor to the hallway.
cheers.

[jay]

hi yep i agree with dave floor will deffinently need to be tight

[Dave]

You take it up and screed the floor......

Floating floors are very prone to movement as they are not directly fixed to anything..so all that supports it is the poly base.....Not good to tile too...and even if you over board that dose not guarentee it will be ok...

[goodjay]

re-screed it!!?? noooooooooo
i can do it as im a plasterer aswell but i really dont want to! lol
all the bathroom is done now except the floor and the last thing i want to do is get all messy doing a screed!
so is a new screed the ONLY way to go with a floating floor then mate?
bearing in mind its a tiny floor. so was hoping some think ply would be sufficient??
cheers. Jay

[goodjay]

oh and what did you mean by "could puncture the DPM"??

and hello Jay. cheers for the top tip! lol just kiding.

[Dave]

Depends on how big a fixing you put in the floor to pull it down tight.....drilling to deep will puncture the damp proof membrane..

I have see one bloke use 6 inch frame fixings to pull a floor down...after all the poly foam base is quite thick....and you could still have compressive issues later...

If you can get it stable and it's small floor then a part S2 type adhesive might hold the tiles and a highly flex grout mix...

It's all upto your judgement of the floor though...

We can only advise what will and won't work...as we see it, and without inspection ..if you see what we mean...

[jay]

sounds like rip it out prime render w/p tile grout silcone is the only fix

[goodjay]

heres some pics if it helps?






yeah i know what your saying dave. i just have no idea how much play you can get away with when tiling.
in the pics, where the join is between the two boards, the main part of the floor (on the left) starts to bounce about 30cm from the join and when you tread on it, it lowers 2mm to the same level as the new board ive put down.
as the main part of the floor with obviously move due to the ploy, i was thinking that atleast it would move evenly and as one and that the Ditra matt would cope with that as thats what its for?
just havent a clue about the join where the main floor bounces and the the new floor doesnt.
what if i just screw down the bit of the main floor where it meets the new floor as best i can like you say??
the adheisve i have is BAL RAPIDSET CERAMIC FLOOR ADHEISVE. (suitable for porcelin tiles?)
cheers again guys.

[Dave]

Jay...lets wait till some of the other members see this and input as well...then you get more than one view on it...

then you can decide what you think will be best for you......i know what i would do but lets wait for some more input..

[goodjay]

yeah no worries mate. more the merrier.

one thing i was going to say was that, say i hadnt ripped up that bit of flooring, then the whole floor would be a solid flooting floor, in which it would all move as one whole piece and by using Ditra matt, the Ditra would cope with any flex as thats what its desinged for.
so as its only a small slither of flooring at the side of the room, the only time one might stand on it is when they are sitting on the toilet and their left foot is resting on it. therefore hardly any weight will ever be put on this join between the two boards. so would that be a good enough exscuse not to worry about it?
sorry for all the questions. im still learning and i dont want to mess up my bathroom after ive spent ages getting the walls and widow reveal and boxing spot on!

[Dave]

Jay....Ditra is NOT designed to cope with flex ( deflection)...it is for a few purposes like lateral expansion issues and water proofing....crack isolation...vapour equlaisation etc etc...but deffo not deflection....


please visit schluter.uk for more info if you need it..

[goodjay]

[jay]

that joint will travel through eventually just like a concrete exp joint tiles (floor)are solid and designed to go on a solid base timber floors have to be strengthed any give and it will self destuct sorry

[goodjay]

right ok. i think ill just screw it down best i can then fix some ply over the whole floor. hopefully that should be enough. (?)
any ideas as to what the minimum mm ply i can use after seeing the pics of my floor? just worried about having a massive height difference from the bathroom to the hallway.
thanks for all your help guys.
Jay.

[Dave]

Also.....that adhesive isn't suitable....for a fighting chance use mapei keraquick and latex plus.....the one you have will not cope with deflection like the mapei combo will...

[dave kelly]

hi guys Im a new member but couldnt resist chipping in! lifes a risk! I would lay a 9mm ply and screw at 300mm centers, use a flexible floor adhesive and flexi grout and take the risk! if all fails MOVE! all the best Dave K

[goodjay]

Also.....that adhesive isn't suitable....for a fighting chance use mapei keraquick and latex plus.....the one you have will not cope with deflection like the mapei combo will...

cheers for that mate.

[smurf21]

If you really want to tile on it overboard with nmp and use a two part flexi the nmp will give extra rigidity....BUT YOU ARE STILL ON A FLOATING FLOOR AND WILL STILL GET SOME DEFLECTION SO THE RISK IS YOURS TO TAKE.
imo i would choose an alternative floor covering.

[lucius]

The time youve spent on the forum asking the question you could have screeded it, proper job the only way.
Lucius.