Floorboard preparation problem - need help

[lukio2011]

Hi guys I have a quite common question but maybe I could get a precise answer to few questions. Im looking at tiling hall and kitchen in 1950? semi-detached. Hall and half a kitchen got floorboards and the other half concrete.
So I would like to do a good job with sub floor preps and here arise my questions:

1. would adding screws to floorboards and plying it over with 12 mm ply would be ok?

2. Or do I have to remove floorboards and add nogings and than ply with 18 mm plywood, but here is my maybe most important related question:
CAN I TILE STRAIGHT ON 18 mm FAR EASTERN PLY WITHOUT HARDIE BECKER? Its a hall so water leaks are not a problem.

If yes how do I prepare /treat plywood,

or Is it a complete NO NO?

3. my 3rd question is about installation hardie becker on plywood. do i always have to use thinset and screws or just screws? and what about concrete subfloor - thinset and maybe hammer fixings? I watched some material on youtube but I couldnt find general guidline?

4 And my last question. would it be ok to overlay joint between wooden floor and concrete floor with hardie becker fixed with thin set and fixings on both sides to prevent cracks in this vulnerable place - or mayb someone knows better idea?

Any answers much appreciated. Many thanks!

 

[macten]

If floorboards are in good shape with no deflection then I would personally overboard with 6mm cement backer board.
I use a specialist glue and screws for fixing to timber and I would use an SPF addy to fix to the primed concrete.
Leave a joint in the backer board where the two substrates meet and follow the joint through to the tiles using a movement profile or silicone.

 

[lukio2011]

Thanks a lot Macten for your reply.
Can you also tell me which adhesive would you recommend for fixing hardie backer onto wooden floor?
And correct me if I'm wrong but you wouldn't overlap joint between two substrates with hardie backer but fill it with something flexible - and insert jointing strip between tiles on the top - or should I just align tile joint over the joint of substrates?

And finally what are your views on tiling on plywood?

I invite everybody to share their views on these things.

 

[macten]

I stopped tiling onto ply 3 years ago. Cement tile backer boards work out about the same price as good quality WBP ply and is faster to cut and install. Then most adhesives need to be a 2 part which is even more cost and at the end of the day tiling on wood has inherent potential problems that cement backerboards don't.

I use a single part flexible bagged cement adhesive to stick boards down with. This acts to fill any voids between the backer board and the floor boards and the screws provide the fixing. Over cement I just use the SPF.
I wouldn't recommend bridging the 2 substrates with the board unless it was a tiny area. I always try to set out so a grout line will fall where the transition is and use a movement profile or simply silicone instead of grout. You can even make your own movement profile by using metal tile trim either side of the joint and fill with silicone - this adds extra protection to tile edges than silicone alone.

Have a look at this old thread of mine - I had the same kind of thing to do:

http://www.tilersforums.com/tiling-forum/27843-hall-kitchen-floor.html

 

[lukio2011]

Thanks again, looks like you are the only one who gave me any answer so far macten but that's ok. Thanks for detailed explanation - that's what I needed. This plus other useful posts I have read here and I'm ready to install hardie backer boards - I got them today at £10.49 including Vat - i don't know if can be bought cheaper?

The guy in topps tiles said I should prime substrate with their BAL primer which, someone correct me if I'm wrong, is just SBR but more expensive so im I'm planing to use cheaper brand. I dont know one thing - should I apply it on cement board as well?

 

[Gazzer]

Why do you need more people to give you the correct info ?

 

[Gazzer]

I dont prime backer boards but a quick wipe over with damp sponge is a good idea to remove any dust

 

[charlie1]

I would not use backerboards directly on to your floor boards no matter how deflection free they are, install ply then hardie

 

[cam_low]

Does it not advise to not prime bb

 

[lukio2011]

Hi Sir, I don't but I guess that experienced tradesmen work out their own way of doing things and there might be few correct ways of doing something and I'd like to learn about them, so I that's what I meant.

thanks for that info on wiping cement board. Am I correct on that the bal primer is just SBR no different to other brands?

 

[Dougs Third Go]

I wouldn't use hardiebacker onto concrete, instead I'd make up the levels with self levelling compound.

 

[macten]

SLC would normally work out cheaper, choice is yours.

The concrete will need priming, boards a wipe down with damp sponge should suffice.

 

[macten]

If you have a CTD store near you they will be around £9 and often have deals like buy3 get 2 free

 

[lukio2011]

£9 per board is a good price I need to go to CTD store.
And to let everyone know I've consulted the floor with my joiner and he said that it is sound, well laid t&g and there is no point in changing it for ply so I've installed hardie backer and have screeded over the concrete part. Thanks everyone for help