subfloor for tiles???

[coach]

Hi all,
I'd like your help. Me and my other half have been arguing for days over our kitchen floor that we are tiling. I say we should remove the chipboard that is down now and replace it with 18mm wbp plywood with aquapanel on top but he says that removing the chipboard and replacing it with plywood is a waste of time and we can simply put the aquapanel down over the chipboard and tile over that. Please help! I've heard people say you can tile directly over chipboard but I am weary. Any experts out there that can settle this arguement???

 

[gcol]

Glad to settle the argument - you're both wrong.
If you can handle the increase in height - screw (every 200mm all over the sheets) 12mm WBP ply over the chipboard and tile onto that using Bal single part flexible powdered adhesive. If the chipboard is very good, then you may be able to get away with 9mm ply. If not, remove the chipboard and replace with 18mm WBP ply (25mm is better) and tile onto that with the adhesive already mentioned. Add extra noggins under the joints. Finish with a decent flexible adhesive - Bal is fine. I'd recommend grey for floors. Don't use white or ivory cause it gets grubby quick. Come back if you need further advice.

 

[coach]

Thanks for your help. The whole arguement started because we cannot spare any height on the floor due to the appliances. This is why I suggested to remove the chipboard and replace with plywood. Our neighbor came over and said that you can just put PVC over the chipboard and tile over that which I didn't agree with. The floor seems solid but I've heard that chipboard is never a good subfloor. So, do you think the aquapanel is unnecessary and we should just use plywood?

 

[masona]

So, do you think the aquapanel is unnecessary and we should just use plywood?

Take out the chipboard flooring and use WPB (exterior) plywood and as mentioned above put in extra noggins (joist) including where the joint of the plywood butt together.

The advantage of this also will give you the chance to inspect the joists condition underneath and any extra wiring or plumbing etc.

 

[coach]

OK, thanks. I'll let you know how it goes if I can get my way.

 

[coach]

OK, convinced fiance to screw down 12mm plywood but I'm still nervous about tiling directly over plywood and wanted to make sure it was safe to do so. Everywhere I've read says never to tile directly onto plywood that it won't stay put. Should I use Hardibacker or something like that? We bought the bal single part flexible adesive...
Thanks so much for your replies.

 

[Bowness72]

I tiled my bathroom floor onto 12mm ply with no problems, although it was screwed down to the existing floorboards at approx. 300mm centres for the full perimeter of every sheet.

If you can fix regularly to every joist and noggin (in middle of sheet as well as perimeter) I don't think you will have a problem.

I also applied watered down PVA a before tiling to seal it.

 

[coach]

I'm so confused because I get different information the more I research this topic. I read somewhere that you shouldn't use PVA before tiling because it doesn't completely soak into the wood and when it gets wet it becomes sticky again. Bowness 72, how long ago did you tile your bathroom? Maybe I should just stop reading so much about the subject or else I'm going to end up having nightmares about tiles!

 

[Thermo]

go with gcol on this one. you dont need pva.

 

[coach]

Thanks Thermo, I thought gcol would be the one to listen to after reading a lot of his advice on these forums. I've had a lot of laughs reading the rants between him and joe-90. Who'd of thought a DIY forum could be so entertaining!

 

[Bowness72]

I did my bathroom two years ago and not a problem (touch wood). I used WBP ply so I didn't really need the PVA but I had heard bad stories of tiles on a timber floor so just did it just incase. A bit belt and braces but for the sake of such a small task I though worth it. The PVA was watered down (as per instructions on carton) because the water carries the PVA into the ply, although not sure how well with it being WBP ply.

 

[coach]

Thanks, Good to know. Like you, I've heard bad things about tiling over plywood, it seems like you get so many conflicting opinions of how to do the same job so it becomes very confusing for an amateur. I'm glad I stumbled accross this site and have been able to get advice. Wish me luck!

 

[gcol]

When you screw down the ply, screw it every 200mm (8") all over the sheet's surface - not just at the edges. Follow the instructions on the adhesive - it might say for tiling onto ply you must use their primer. If it says this, use it and don't be tempted to use pva as a shortcut.

 

[masona]

Watch out for any cable and pipe etc

 

[gcol]

Oh yes, as masona rightly says - buy screws short enough so that they do not go through the floorboards.