Wedi Tilebacker Board Query

[Pebble]

Hi, I am looking to install a Wedi Fundo shower tray by cutting out the chipboard and then securing 6mm ply on the joists (I will strengthen by adding more joists) followed by the tray. By fitting the tray on the joists + ply I don't have such an issue with levelling the rest of the bathroom since the Fundo tray is 40mm in height. It is the levelling of the rest of the room where my question lies. I intend to prime the existing chipboard and then secure 20mm Wedi Tilebacker board to the rest of the floor (using flexible adhesive), followed by electric heating matts. In order to bring the total level up to the height of the Fundo tray I may need to add a layer of screed onto the heating matt prior to tiling.

My question is whether it is ok to put the 20mm Wedi Tilebacker board straight onto the chipboard floor without first securing a layer of plywood ? Is the Wedi tilebacker strong enough to avoid having to first put Ply down.

Thanks

 

[Gazzer]

Moved to correct forum and deleted duplicate thread .

 

[Thespanishtiler]

you should be working to the preped floor height of the room as a level to set your fundo.

ie lift all the chip board
lay new flooring (ply)
overlay with cement boards (hardie backer)(or insulation boards)
allow for ufh and slc on top(6mm)
allow for ci matt if being used(4mm)
now set your fundo to this height (trimming of joists and counter joisting may be needed)
use min 12mm ply for counter boarding

once set as per mfrs instructions lay ufh and slc over to level of fundo threshold

lay ci matting

tape and tank as per products you are using

Tile

 

[Pebble]

Thanks. Can you let me know what thickness ply to use for the new flooring once the chipboard is removed. Also what should the thickness of the cement boards be on top of the ply ?

Sorry for my ignorance, what does "slc" stand for and "ci matt".

The fundo is 40mm high so are you saying I should put the Fundo on the new plywood (thickness tbc) + cement boards (thickness tbc).

I am worried about the step up into the bathroom if I set my fundo on the preped floor so is there any clean way of minimising the step up into the bathroom ?

 

[Thespanishtiler]

slc is self leveling compound (you need one suitable for ufh)

ci is crack isolation matting for decoupling the expansion and contraction of the ufh from the tiled floor

ply to be min 18mm with extra noggins at joints all screwed and sealed on the back and sides, 6mm cement boards laid ond spf and screwed.

the fundo sould be let down into the joists to be set at a level that correspondes with your prepped floor after the ply, cement boards, ufh, slc and ci are all laid.

hard to explain the ins and out of wetroom prep and to be honest i would recomend a local pro did the work for you.

off out now so wont be on line

 

[Thespanishtiler]

also re my 1st post you should lay the slc to a level that corresponds with an allowance for laying the ci on a bed of spf so it is dead level with the fundo threshold once down.

 

[Pebble]

Great thanks for clarifying that. So it seems that it is ok to lay the fundo tray directly onto the joists (assuming I add counter joists for strength).

 

[jay]

Try this http://www.google.com.au/url?sa=t&s...kNjYAw&usg=AFQjCNEAhHGTtJzF0pm9b1Hcz5iJfYGx2g

 

[Thespanishtiler]

Great thanks for clarifying that. So it seems that it is ok to lay the fundo tray directly onto the joists (assuming I add counter joists for strength).

no it is not !!!

You have to have counter joists set to carry 18mm ply interspersed between the joists so as the ply is level with the height you have trimmed the joists down to. trimming is needed sometimes so as the fundo threshold is at the level you are preping the main floor level up to.

try reading the literature on fitting the wedi fundo, the supplier you are using will provide this for you

 

[DHTiling]

IMO you should not be trimming joists..?..

You can get trays that are now only 22mm thick and span the joists without the need to board out between the joists for support.

But you deffo DO NOT trim joists down in thickness/depth etc..