# Forum Home Renovation Waterproofing  Puddle flange installation question.

## ChrisJC

Hey Guys, 
I was looking for some info regarding installation of puddle flanges on 6mm cement tile underlay. I found an old post from 2011 in which Oldsaltoz mentioned recessing the sheet with a cup grinder, or placing the flange below the underlay, Just to confirm, is it still an acceptable method to place the flange below the underlay and have 20mm clearance around the flange (ie 40mm larger dia than the puddle flange)? 
Many thanks
CC

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## JB1

Definitely do not use a 6mm cement tile underlay for your shower.  
Scyon wet area flooring is 19mm.

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## ChrisJC

6mm underlay is suitable for wet areas. Floor is particle board on steel beams. It would be a major job to remove and replace. The existing tiles were directly over the particle board with a membrane of course.

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## Oldsaltoz

> Hey Guys, 
> I was looking for some info regarding the installation of puddle flanges on 6mm cement tile underlay. I found an old post from 2011 in which Oldsaltoz mentioned recessing the sheet with a cup grinder, or placing the flange below the underlay, Just to confirm, is it still an acceptable method to place the flange below the underlay and have 20mm clearance around the flange (ie 40mm larger dia than the puddle flange)?
> Many thanks. CC

  Hi ChrisJC,
With tile underlay install, most waterproofers will simply cut a hole 20 mm larger than the flange, then Sikaflex the exposed area and insert the flange, then apply some pressure (Stand on it) and fill the gap making sure they overlap onto the flange and the floor sheeting. 
The flange is only 3mm thick, plus the film of sealant so the flange should end up just below the sheeting level. 
Good luck and fair winds.  :Smilie:

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## ChrisJC

Thanks again Oldsaltoz. I have the flanges si I'll do as you suggested and cut a larger hole in the underlay then sikaflex the flange to the floor. 
Cheers
Chris

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## Oldsaltoz

OK Chris, just make sure you cover the exposed top of the flange with a sealant so the waterproofing membrane will stick well, just don't be tempted to continue down inside it. 
Good luck and fair winds.  :Smilie:

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