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Deleted member 46792

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Hello

I am a DIYer and after a successful shower tile project set about tile bathroom floor. Victorian terraced house, previous floor - exposed original floorboards. After research and consultation with a carpenter, I understood that the deflection wasn't bad and that I should screw down any loose-ish floorboards and overboard with 6mm No More Ply using the NPM mega strength https://www.tilersforums.com/forums/tile-adhesive/. Having done this and having been pretty pleased with my efforts I asked a tiler (and paid for consultation services) round to give me his opinion. He said that my floor has too much deflection and that the grout and possibly the tiles will crack. He gave me a couple of suggestions - the most expensive being to start again and lay down 18mm ply. This could be tricky as I understand that even in the event of a nuclear war the NMP will probably still be sticking to the floorboards because of the strength of the https://www.tilersforums.com/forums/tile-adhesive/. The other option he said was to get some expensive https://www.tilersforums.com/forums/tile-adhesive/ - bal single part fastflex I think it was - which has an elastic ingredient and get flexible grout that you can add an additive to that will make the grout very flexible.
This evening I have been wondering if it isnt possible to double up with overboarding with a layer of ply or another layer of NMP. I also did a test that I have read about which involves filling a glass of water and placing in centre of room and getting biggest person you know to jump about a bit. Well I fit that profile so I have done that and no water was spilt. I can see some deflection in the floor but I am not sure what to think now. I am not sure what is acceptable, what remedial actions to take..

Anyone got any thoughts on this? I dont want to do a cr*p job but I dont want to pull the house down!
 
OP
D

Deleted member 46792

what size is the floor and what tiles are you wanting to fix?

Hi Julian, the room is 3m x 2.4m but there are bath, seperate shower tray and sink unit areas that wont be tiled. Its about 4.4 sq. metres of tile. I have bought 60 x 30 porcelain tiles but they were cheap and would replace if something more suitable would go towards fixing the problem..?
 
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K

Kevbos

Go over ply with 12mm ply screwed alot .use ditra mat or equivalent over this .tiles won't come up with a flexible https://www.tilersforums.com/forums/tile-adhesive/ and grout
 
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J

J Sid

I would be very surprised if a floor has that much movement and if it has is it going to hold a bath full of water!
@Kevbos wouldn't 12mm hardie board be better and no need for ditra.
 
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D

Deleted member 46792

I would be very surprised if a floor has that much movement and if it has is it going to hold a bath full of water!
@Kevbos wouldn't 12mm hardie board be better and no need for ditra.

Hi Julian, do you mean you doubt whether the deflection is significant? Would you agree with Kevbos that its probably an idea to add a further 12mm?
 
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K

Kevbos

Might well be .usually floor flexes because joists bouncing .I just cover myself in instances where floor bouncing .
 
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J

J Sid

not seeing the job, but if the floor boards have been screwed down and the nmp was laid, I would be surprised if a floor of that size had that much bounce. If you think it has then laying 12mm hardiebacker board as per the manufacturer instructions would help.
 
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K

Kevbos

I lived in sweden 2 years .they use plasterboard on floors and tank it .can't get insurance on house if you haven't whose right ?
 
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S

Stef

If there's bounce in the floor then how is Ditra going to help??
Issue should have been fixed before nmp was fixed.
Option I would choose is get yourself an elastomeric https://www.tilersforums.com/forums/tile-adhesive/ like the BAL you have been told about, you can make your own up with certain addys & additives & fix your tiles.
If it fails then you go back to the start.
 
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K

Kevbos

Or strengthen the floor before you start to tile .like you should do over any floorboards .6mm ply is not sturdy enough .at least 12mm 18mm preferably should be used .and ditra was made for a reason
 
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S

Stef

Or strengthen the floor before you start to tile .like you should do over any floorboards .6mm ply is not sturdy enough .at least 12mm 18mm preferably should be used .and ditra was made for a reason
Ditra wasn't made to take deflection!!
 
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D

Deleted member 46792

I lived in Sweden too. They do a lot differently!

Ive been in again and looked at the bounce. You can definitely see the floor move but its mm rather than a cm. And im pretty big. And its in two small areas not all over.

Im going to try with the elastomeric https://www.tilersforums.com/forums/tile-adhesive/. Thanks very much for all the help.
 
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K

Kevbos

No but was made to help eradicate movement after preparing a floor properly

Good luck with the bal .just look up tile overy floorboards .that 2mm will transfer into cracks

It will cost 100 pounds to strengthen floor why not just do that
 
Last edited by a moderator:
OP
D

Deleted member 46792

Good luck with the bal .just look up tile overy floorboards .that 2mm will transfer into cracks

aaargh...the 6mm NMP was supposed to do the job..as far as i understood 6mm NMP was supposed to do the job of 18mm ply...
 

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