Do I need to tank my en suit floor?

[Ben100]

Hi all,

 

I'm working on my en suite and have a question on waterproofing the floor. The en suite is on the second floor, with a build-up of 22mm OSB and 10mm concrete screen with electric UFH in it. The shower tray and cubicle has been tanked and taped, and I've used hardi back board on the walls.

 

Do I need to tank the rest of the en suite floor outside of the shower tray? Or can I tile over the screen with a water resistant adhesive and grout?

 

Cheers!

[Pocster]

I didn’t . I assume it doesn’t need to be waterproof as outside the tray .

I would recommend a decoupling Mat . Then you use flexible tile adhesive on that and flexible grout .

[SimonD]

If you take the BBA certificates seriously, both Norbord (SterlingBoard) and Kronospan say the OSB:

 

"When used in high risk areas, such as kitchens and bathrooms, the panel must be protected from wetting, eg by providing a continuous waterproof covering, turned up and sealed at junctions with walls and where services pass through the floor."

 

Here's a link to Sterlingboard BBA - https://www.norbord.co.uk/wp-content/uploads/2019/11/bba-cert-osb3-flooring.pdf

And for Kronospan - https://uk.kronospan-express.com/en/ajax/express_services/download?args[0]=express-services&args[1]=downloads&args[2]=United-Kingdom&args[3]=certificates-and-datasheets&args[4]=kronospan-osb-flooring-bba.pdf&show=1

 

I've tanked the osb directly in my bathrooms over the whole floor using liquid membrane over which I'll install the final floor covering as overall it's cost me about £60 thanks to a deal. For me it's worthwhile insurance. With the kitchen I'm just applying the membrane below and around the wet areas.

 

As for longevity when not protected, I had osb subfloor where there had been a pin hole leak in the central heating system spraying water up against the osb under the suspended ground floor. It lasted 2 years like that and what alerted us to it was a large black wet area appearing in the floor. Despite this the floor area didn't lose its structural integrity - you could still walk on it an a sofa leg was resting in the middle of the patch.

 

 

[Onoff]

4 hours ago, Ben100 said:

Do I need to tank the rest of the en suite floor outside of the shower tray?

 

How big an area? You can get a 7.5m2 tanking kit for circa £50. No brainer for piece of mind imho.

[SimonD]

2 minutes ago, Onoff said:

 

How big an area? You can get a 7.5m2 tanking kit for circa £50. No brainer for piece of mind imho.

 

Spot on, here's one https://www.sealantsandtoolsdirect.co.uk/wet-room-systems/aquaseal-wet-room-tanking-system-large-75-meter-kit-aqwrskit

[Big Jimbo]

Would'nt do any harm, and cheap enough.

[Ben100]

Ok, thanks guys!

 

It's a small enough area, just another job to do...

Edited June 3, 2021 by Ben100