# Forum Home Renovation Waterproofing  Bathtub waterproofing

## Capelli84

Hi all,  
I am redoing an old bathroom and will be installing a new acrylic bath in a corner with brick walls. Because of the state of the walls after the demo works i am planning on relining the walls with villaboard (yes with mechanical fixings as well as masonry adhesive). 
I see the general wisdom on bath installation is to rebate the lip of the bath into the wall. Happy to do this, and will also support the bath the full way around with timber frame clad in villaboard. On the non-wall side of the bath i will be setting the framing and villaboard back enough so that the tiles fit flush to the bath (i.e. no horizontal tiles against the bath).   
Because of timing with the plumber, the bath will be installed (plumbed) before the walls are lined with villaboard. So my questions are in relation to appropriate waterproofing around the bath? 
On the non-wall sides i guess i can follow the membrane up the villaboard to the underside of the bath, and really water would have to defy gravity to get up over the membrane and cause any problems.  
On the wall sides I am a little more unsure. I guess the lip of the bath actually acts as a waterproofing lip? So the membrane would cover all of the villaboard down to where it meets the bath? But its that junction there that i am unsure about in particular? 
Any insights would be much appreciated.

----------


## Oldsaltoz

The sheeting on the wall sides should be installed with a 3 to 5 mm gap between the sheet and surface of the bath. This gap is then sealed with a sealant, Sikaflex 11FC is what I use. Also seal the corner joint as above. 
I the bath has a sower over it you need to waterproof the wall sides at least 150 mm up from the bath lip and the corner wall joint to at least 1.40 m. 
If no shower over bath no membrane required to meet the standards. 
Note: The abobe is for a standard installation. If your bath is an Island mount please advise for revised advice.

----------


## Capelli84

Thanks for the response. Yep its a standard install so your advice applies.  
Its not a shower over bath, but the shower area will be unenclosed and hard up against the bath (its only a 1200mm bath, so same length as the shower area). With that in mind I will be applying shower waterproofing requirements to the bath walls.  
I guess what i was wondering about was how the membrane would interface with the bath surface. So after the gap is filled with Sika, the membrane would then run over the villaboard onto the sika and terminate at or just onto the bath (acrylic) surface? Obviously conscious of not wanting membrane visible on the bath surface.

----------


## Oldsaltoz

> the shower area will be unenclosed and hard up against the bath

  In that case I would advise you over flash the shower end of the bath. The membrane on the bath only goes down to the gap, not over the sealant. You might want to re seal this one day. After the tiles are installed a second seal between the bath and tile bottom will provide a clean line. No membrane in contact with bath at all. You will need to cover the wall to bath joint that will end up inside the shower, add some sealand prior to membrane si it some movement capability.  PS. You can avoid a messy clean up by masking off the bath. 
Good luck and fair winds. :Smilie:

----------


## Capelli84

Thanks for that. I have attached the plan, to confirm the layout.  
What do you mean by 'over flashing' in this context?

----------

