Tiling on wood and concrete combined flooring

[Ren+]

Hi guys

I have an area of about 50 sq.m (hallway, passage, kitchen & dining room all linked) to tile of which 7sq.m is planked timber flooors over joists. The wood floor is in the hallway and covers about half the hallway. The wood and concrete meet level and is currently carpeted. I'm aware that I will need to put a movement joint where the wood and concrete meets. Permitting the boards do not have excessive deflection in them, would it be best to overlay the timber floor with backerboards and if so, what adhesive (can you mention a brand as well pls) do I secure them with? Do you recommend screws as well. Secondly, whatever you secure to the wooden floor, it will now be higher than the concrete as a result. How do I overcome this? Would you recommend an slc to loose the height variance over a larger area?
Thirdly, I've seen a post elsewhere where advice was given to put ply (and not the thin stuff I'd imagine either) under the backerboard if there is excessive deflection in the wooden floor. The floor variance would then be more pronounced ... how do you overcome this withthe variance making it all the harder to lose an obvious slope.
Any advice on the above questions will be greatly appreciated. Wooden floors have been my worst nightmare when it comes to tiling.

Thx
Andre'

 

[Martino]

what boards are on the joists?....floor boards or chipboard sheets?....could u not remove these put more noggings in the joists to make them secure, ply with some 12mm and hardie with 12mm? then youd probs have like 6mm difference? which you could lose with some rapid set? not sure if u could go for 9mm ply then 12mm hardie?

 

[Ren+]

Thx for your input Martino. They are planks, most likely 18 to 20mm. I would have thought that noggings would give sideways support to the joists. If the joists run longways and they obviously have the deflection, how would noggings help if they were being fixed at intervals to the joists? Correct me if I'm wrong. I've never tried the backerboard & ply option so all advice will be good thx.

 

[Martino]

addiing more noggins will help with the deflection, sometimes on old houses u need to put wedges in the origional joists where they sit on the sleeper walls,...basically where the ends are if that makes sense.....the more noggins the stringer your floor will be ....you could go for 15mm WBP and 6mm hardie thats gonna be your closest!

 

[Ren+]

Thx again Martino. I see a lot of tilers mention that they do not tile a wooden floor without putting down Ditra first. Do you use ditra at all or is there anyone who can shed more light on this please.

 

[Concrete guy]

If the surfaces are all the same level and you have enough height for a 12mm reinforcement I would do the following (and fitted this spec for many years).

Glue (SPF adhesive) and screw 12mm Aquapanel across the whole lot. Drill, plug, glue and screw using washers on the concrete area. Tape all the joints

If there is excessive movement at the join between the concrete and the floorboards then reinforce this area first.

The above will tie the two substrates together and give a stable floor on which to fix. I see no value in an uncoupling membrane on this installation unless there is a possibility of noticeable shear movement in the form of expansion and contraction.

 

[Ren+]

Thx for your post ATSDT. I get what you're saying with the aqua panel to solve the wood floor prob and carry through the same height throughout and it makes sense as being 'fail proof'. It just feels strange to put an extra layer of cement board on existing stable screed throughout the rest of the project (another 43 sq.m) at the cost of at least £15/sq.m plus labour. I'm not trying to be difficult, just trying to minimise cost wisely.

 

[Concrete guy]

If the wood is very stable, then overboard at 6mm with a healthy overlap to the concrete and screed the rest or feather the 6mm down over a few meters.

 

[Ren+]

Yes, thats the crux, to make sure that the wood is stabilised maximum ... noggings, etc. Even pulling the exist planks/chipboard off and then 18mm WBP and overboarded 6mm backer and then feathered as you mentioned. Thx for your input on this one.