Floor tiles lifting after laying. Please help

[Unregistered]

Hi I would be very grateful for your suggestions/thoughts.
Details:
-Laying ceramic floor tiles 33cm x 33cm in the conservatory - 15m sq..
-The floor was chipboard and I layed 12mm WPB plywood screwed at 25cm intervals.
-Coated with BAL - bond SBR
-Used homebases Evo-Stik Tile a Floor Adhesive (for Stone and Porcelain).

Steps so far:
I have made the adhesive as per instructions, I have nearly laid 3/4 of the floor!! Tiles are spaced 5mm apart using spacers. Adhesive was spread on using a floor notched trowel. I have only been able to lay around 4-8 tiles each evening due to work. After laying they have not been stood on or touhed for at least 24 hrs, despite packaging saying set within 2-3hrs.
Problem: I have started noticing line crackes appearing around the tiles. I popped a small trowel under one and it popped up. I am now going around all the tiles and most appear to not have stuck and sound hollow and their is movement. Some are just popping up when i apply a bit of force to the trowel. When lifted adhisve does not appear to have stuck well to floor!
I am not an experienced tiler, I have layed the kitchen floor tiles and their was no problem although this was much smaller, say half the size and I used homebases ready made adhesive.
My questions:
1. Ok so my main question is why is this doing it. My own stupidity? Product problem? - I am on my 3rd bag and the tiles appear unstable throughout the room which used all ahesives so i dont think so.
2. Could this product just be unsuitable for the area? The room does get very hot - would this cause the adhesive to dry out more than normal before grouting etc and cause it to crack?
3. Should i try an aleady made adhesive for wooden floors? Should I have gone with the more expensive BAL adhesive or some other products.
4. Should i rip them all up and try again?
I'm pretty peed off and disappointed. I had a really bad couple of weeks at work and now it look like I gotta do this again and time is a bit tuff to do this but cannot afford anyone to come in and do it. Plus i think this is someting i can do. Be very grateful for any help/suggestions.
Many thanks. Kevin

 

[Time's Ran Out]

Kevin - My first thought would be to check the code/date on the adhesive and contact Evo stick to see if they have had any other batch problems! As I have never used Evo Stick I cannot comment on its suitability for your project. However I'am sure you checked that if was a fast set FEXIBLE adhesive suitable for tiling onto wood.
The plywood on top of chipboard is obviously going to have tremendous movement in a hot conservatory (they go + 100degrees) and with the weather of late you could be right with your assessment. However as you fixed the tiles in an evening the adhesive should not have been so affected.
When I used to use plywood it was always screwed at 150mm so your 250mm seems inadequate.
You don't mention what depth floor trowell you used or if you solid fixed the tiles to a minimum depth of 10mm.
Without being able to look at the tiles/adhesive I have to be vague in the response but my first thought is the way i would approach the problem and if unresolved I'd use a Mapei flexible adhesive.

Timeless John.

 

[Perry]

did you prime the surface and was it rapidflex ?

 

[Unregistered]

Many thanks for your responses. Much appreciated. I have decided to pull the tiles up and they are all up now. Will have to spend ages removing the adhsive from the floor and the tiles.
Timeless john -
I will look for the date/code and will follow up if necessary. Thanks. It says it was a fast det flexible suitbale for wooden floors. Confirmed by the Homebase sales assistant (although not relying on him too much).
Most tiles were fixed in the evening when it was cooler. The first lot were done during the day (around 20 tiles) when it was hot but they all appear to show the same problem, that is they have not bonded well to the floor.
Do you think that it is worth putting more screws in to reduce movement now tiles are up? This will make it 125mm apart then.
The trowel is a floor trowel form DIY. The notches measure 10mm height and 20mm width.
So depth should be ok at 10mm.
I have had a look at Mapei and it has good reviews. It appears cheaper (which is good for me, although i dont want to cut quality) than BAL single part flexible or bal rapidset flexible which I was considering. Have you had experience of BAL? Where would be the best place to get the mapei product.
PJC:
I used BAL SBR which is a bonding and primer. I was told this would be better than a PVA as any water can affect the PVA, not that there will be any.

 

[DHTiling]

GUEST!!..If you join up ( which is free) we can reply quicker as guests posts have to approved first..

 

[Perry]

most company's tell you to prime the back and edges not the face

 

[kevb]

Ok just registered, thanks.

I only primed top and sides, not underneath. As this was a bonding agent as well I was told to do top of tiles and not underneath.

 

[Spud]

floating floor perhaps ?

 

[kevb]

The subfloor i think is joists with the chipboard over it. It looks at least 18mm. It appeared to be screwed at regular intervals. There did not appear to be any movement and therfore dont think it is a floating floor?

 

[Daz]

Did you trowel the adhesive directly onto the floor and then backskim the tiles before fixing? Or just back butter the tiles before fixing?