Ceramic Tile Underlay for Bathroom

[Gooner]

I am about to install some of the JH Ceramic Tile Underlay on my bathroom foor.

I understand that I need to have flashing on the wall/floor intersections and that I need to apply waterproofing membrane on the entire floor and at least 30cm up the wall in the non-shower areas before tiling.

My question is, I will obviously have to lay down more than one sheet of the underlay. What do I do at the joins (on the floor)? I have not seen any instructions as to what is recommended where the underlay sheets meet.

Do I silicone up the joins and then apply the waterproofing?

Can I apply a wet area join compound (usually used on plasterboard) before applying the waterproofing?

Or can I simply only apply the water proofing membrane, making sure I saturate the joins to ensure they are properly waterproofed?

Thanks in advance...

[Gooner]

No takers on this one?

How about this question... Should I place/cement the shower base on the tile underlay, or should I cut out the underlay to go around the showerbase and hence cement the base to the timber floor?

I would think to cement it to the underlay, but when I pulled the previous shower base out, I noticed they cut the underlay so that the base sat directly on the timber.

[Dirty Doogie]

The jions between the underlay sheets are filled with polyurethane sealant then covered by a bond breaker tape and a bandage in the waterproofing membrane. The shower base can go down over the underlay , perferabley after waterproofing.

You may need to note that some shower bases need a square cutout in the flooring to accomodate the outlet block. This means you might need to cut through the underlay before installing the base.

[Pulpo]

I'm now in the same boat.

No guide addresses the joins between the tile underlay sheets.

Wall and floor use some fibre glass sheets with water proof membrane but the the tile underlay joins?

I guess that nothing is needed?

I assume its ok to place the membrane over the tile underlay?

It will be a bugger if not, expensive exercise to rectify if not.

Cheers

Pulpo

[arms]

you should put a layer of the waterproofing membrane over the joins then wait the prescribed time as directed then put the full coat over the floor as required ,this will give you 2 seals over the joins

[Pulpo]

Thanks

I was told lay some gyprock mesh tape over the joins before waterproofing.

Pulpo

[SilentButDeadly]

In our shower area I've used Bostik Seal N Flex 1 for the joins between the sheets of both Villaboard and the tile underlay on the floor. The Villboard wall joins have been overlaid with standard jointing compound. The whole lot has then been covered with Bostik Ultraseal to create the water proof membrane...
http://www.bostik.com.au/pdf/datasheet/bostik_seal_n_flex_1.pdf http://www.bostik.com.au/pdf/datasheet/bostik_ultraseal.pdf

[zacnelson]

I would recommend polyurethane sealant between the sheets of underlay. Depending on which waterproofing membrane you purchase, you may not need to use the fibreglass paper. I used Davco K10 which didn't require anything but just painting 2 coats of the membrane (but still with the sealant along the joins).

For joins in the villaboard lining the walls, I would recommend jointing them (just roughly because it will be tiled over) with base coat like normal plaster walls, however do not use top coat firstly because it's not going to be seen and secondly because the tile adhesive will not work properly over top coat.