Waterproof Render For Bathrooms

I will have a bath in the corner with a shower over. Most water will go in the bath but the walls will get splashed.

The walls were prepared as follows:

1. Plaster hacked back to bricks.
2. Bricks mechanically cleaned so no trace of plaster.
3. Cement render coat applied to all walls about 12mm thick. (fully cured)

Do I need to use any tanking system?

I cannot remember exactly what the render guys did. They were from a damp proofing company and I think they mixed sand with portland cement and added something to it. I think the additive was SBR. The finish is deliberately rough and scored.

I tested the wall to see if it was waterproof by directing shower spray over it. This did no damage but the render did absorb some water and took 24hrs to dry.

In the picture, the wall going left runs along the bath and the wall on the right is where the shower will be fixed so the head is pointing leftwards away from the right wall.

The left wall is the inner leaf of a brick cavity wall (uninsulated) and the right wall is a two brick thickness sold brick party wall with neighbour.
I think the neighbour has a shower the other side without any special tanking so some moisture may migrate into my side but you cant tell looking at it.

The tiles are 60cmX30cm X10mm glazed porcelain with 4mm Ultracolour plus grout.

Is the cement render background waterproof enough for tiles to go straight onto?

Presumably a little moisture may seep into the cement through the grout but what harm can it possibly do?

If it was an immersed tiled shower floor that would be different, but here is tanking overkill?

Also, won't putting a layer of something weaken the bond with the tiles?

What did folk do before tanking kits were invented?

render.JPG

80.6 KB · Views: 21

Last edited: Nov 17, 2019

Bond

You could just prime the render with SBR, and use an epoxy grout, l would go with a 2mm grout line.

Epoxy grout sounds difficult. The grout has to be 4mm to line up with the floor. The SBR might do the trick though. Thanks

For the sake of £50 for a tanking kit I would probably just tank it. A shower over a bath is still a wet area IMHO.

The finshed article will be similar to the picture here, so there will be the sides of the bath below knee height where most of the water will go.

What kind of tanking will be easiest and not build out the wall too much? Is it just a case of painting some stuff on?

shoerbath.jpg

17.7 KB · Views: 15

Waterproof Render For Bathrooms

Source: https://www.tilersforums.com/threads/waterproofing-cement-rendered-wall.90343/

Waterproof Render For Bathrooms