Retiling wetroom advice on how best to proceed

[One Day]

It worked on the Ark 1000's of years ago

 

[YT233]

On the wall I removed the tiles from this is the wall where the 3.5mm slabs are going. However, there will be a difference in depth between the old tiles and the slabs.

The total depth of the existing wall tiles is about 30mm this is tiles, adhesive and boarding. Now my new depth with will be 12.5mm plus 3.5mm plus about 6mm adhesive?? This adds up to roughly 22mm I am 8mm short.

To compensate for this difference in depth can I put some plastic packets behind the wedi board to gain the extra 8mm?
Broadfix Levelling Shims Kit Assorted - https://www.toolstation.com/shop/Screws+%26+Fixings/d90/Frame+Fixings/sd1950/Broadfix+Levelling+Shims+Kit/p43092

 

[Waluigi]

Have you put a straight edge on the existing tiles?

You want to get your new ‘tile’ perfectly flush with the existing tiles? First thing is see how flat the tiles are. And how level the joint is. It has to be perfect

 

[YT233]

I have and they are bang on level.

 

[hmtiling]

On the wall I removed the tiles from this is the wall where the 3.5mm slabs are going. However, there will be a difference in depth between the old tiles and the slabs.

The total depth of the existing wall tiles is about 30mm this is tiles, adhesive and boarding. Now my new depth with will be 12.5mm plus 3.5mm plus about 6mm adhesive?? This adds up to roughly 22mm I am 8mm short.

To compensate for this difference in depth can I put some plastic packets behind the wedi board to gain the extra 8mm?
Broadfix Levelling Shims Kit Assorted - https://www.toolstation.com/shop/Screws+%26+Fixings/d90/Frame+Fixings/sd1950/Broadfix+Levelling+Shims+Kit/p43092

6mm adhesive bed is a lot. You'll want a 2/3mm solid bed

 

[hmtiling]

It worked on the Ark 1000's of years ago

It did. Tj can vouch for that

 

[YT233]

6mm adhesive bed is a lot. You'll want a 2/3mm solid bed

What size trowel would you guys recommend? For the wall tiles?

 

[hmtiling]

What size trowel would you guys recommend? For the wall tiles?

Ragni 319

 

[Dumbo]

On the wall I removed the tiles from this is the wall where the 3.5mm slabs are going. However, there will be a difference in depth between the old tiles and the slabs.

The total depth of the existing wall tiles is about 30mm this is tiles, adhesive and boarding. Now my new depth with will be 12.5mm plus 3.5mm plus about 6mm adhesive?? This adds up to roughly 22mm I am 8mm short.

To compensate for this difference in depth can I put some plastic packets behind the wedi board to gain the extra 8mm?
Broadfix Levelling Shims Kit Assorted - https://www.toolstation.com/shop/Screws+%26+Fixings/d90/Frame+Fixings/sd1950/Broadfix+Levelling+Shims+Kit/p43092

Use a thicker light weight tile backer board something like Jacko board or Marmox board

 

[Waluigi]

Pack out with long strips of either ply or plasterboard. It sounds like 9.5mm plasterboard might be suitable?

Doing use packers as you have to pack along the whole length, not just where the screwed are going.