# Forum Home Renovation Waterproofing  Waterproofing against shower base?

## kasperluke

Please excuse my ignorance but I have tried to search for an answer on the forums and haven't found what I am looking for and hopefully someone will be able to answer my questions. 
I have attached an image of the edge of the shower base and then the tile underlay on the floor.... what do I do for waterproofing before placing tiles against the shower base? Do I just run the membrane all the way up to the edge? and fill the gap beforehand with silicon? or does there need to be a flashing of some sort?  
Hopefully that makes sense.  
Thanks in advance.

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## Cecile

I know some pretty knowledgeable folks will likely come in and answer this thread.  It looks as though you have not run the cement sheet under the shower base.  Not sure if it's required but I know that's what I would have done.

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## phild01

If I am looking at that picture correctly, it looks like a cement type shower base and the bathroom floor is a strip timber floorboard with fc sheeting over it.  I would not have done things this way and it would have been better to have the sheeting under the shower tray as mentioned.  I am guessing you will be using a shower curtain meaning water over the floor in that area.  Even a shower screen will let some water out.  From what I can see, any waterproofing will have limited performance and life due to the various movements of the wall, floor, underlay and shower base.  Would you be encouraged to do this differently.  Long ago I did a quick and easy with this type of showerbase over a plywood floor with vinyl floorcovering.  It served a purpose but water was an issue with it.  If the floor is a sheet floor, then I would remove the fc underlay.  Bit hard to comment without more information.

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## Random Username

Contact the manufacturer of the shower base and see what their installation instructions are.   
I've always assumed that those bases were designed to sit on top of an already waterproofed floor.

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## Oldsaltoz

The fantastic plastic shower bases have a problem with the waste penetration leaking, primarily die to the 'O' ring not being super clean when installed and also due to movement because the base was not properly installed/supported. 
With the above in mind, the underside should be waterproofed and the upper side overflashed on all sides with walls. 
I can not head nor tail of the picture by the way. 
Good luck.   :Smilie:

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## SlowMick

:d

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## Oldsaltoz

It sure does, now I can actually understand the picture. 
First things first.
If that undertile sheeting is over a timber flooe, you need to remove the shower base and install more tile underlay sheeting. 
It is important, as any leak under the shower will be undetected till the damage has spread, possibly to the point of falling through the floor. 
 A puddle flange should also be installed when the waste is exposed and the waterproofing continued down into the the top of the flange. 
Also make very sure the drain pipe 'O' ring is super clean when installing, they have tendency to leak. 
The gap at the edge of the shower can be sealed with sealanr then coverd with a waterproofing membrane. 
Also note, the bottom of the wall sheets above the tray must be sealed with a sealant and the bottom of the sheets to be waterproofed at least 150 mm above the bottom of the sheet, and shower vertical corner/s must also be waterproofed up to at least 1.80 m. 
All securing nails and any sheet joints should also be sealed before tiling. 
Good luck.   :Smilie:

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## phild01

Still would like to know what is under what looks like hardiflex nailed down with clouts.

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