Does 22mm ply floor need expansion joint between panels? - Tile Advice

[ojtiler]

Hi,

I have 22mm WBP plywood flooring for my wet-room. The ply is laid in two large panels which meet above (and along) the middle floor joist.

The edge of the panels are about 5mm from the wall (so - room for expansion).

Should I be fitting the panels with a gap in-between, too? (i.e. 2-3mm gap along the joint where the panels meet?). The joist is ~50mm, and I would prefer to keep the panels together (without a gap), simply to provide the widest platform to screw down both of the panels.


I would be very grateful for any advice.....



Many thanks.

 

[Ian]

You will need the expansion gap, filled with silicone. What are you putting ontop of the ply with regards to waterproofing?

 

[Stewart]

I leave 5mm between the sheets and then fill with silicone. I then over board with A backer board glued and screwed.

Created on iPhone.....

 

[ojtiler]

Many thanks for the replies and advice....

Is there a specific type of silicone that I should be using to fill the gap? (or is a regular kitchen/bathroom sealant acceptable?)


Bri,
Regarding the waterproofing, I bought an Impey shower former & Impey 'tilesafe membrane' as a combined kit for my project. Impey advise that the membrane can be applied directly onto the plywood floor (after it has been primed). However, having read many other helpful posts on this forum, I can see a lot of advice out there for applying backerboards over the ply before tanking & tiling. As you can see from my earlier post in the Wet-room forum (link below), I've already screwed the plywood down (without a gap!) - and also without any primer on the underside which I now realize is needed to prevent moisture absorption.

I have therefore decided I will unscrew the plywood, prime it and allow a gap between the panels when I re-fit. Quite a few screws to undo, but much less work than lifting the finished floor in a couple of years if it fails!!:smilewinkgrin:

If I over-board the re-fitted plywood with the backerboard (e.g. Marmox), should I fit the over-boards across the joint in the ply?.... or position the joins in the Marmox directly above the gap in the plywood panels? I would be grateful for your thoughts on that.

Photos of my project and many other (as yet unanswered) questions are in my post below. If anyone has time to read & provide any guidance, I would really appreciate it.


Thanks again....

 

[ojtiler]

Sorry,, I forgot to attach the link to my earlier post in the Tanking & Wetroom forum.

Here it is:
http://www.tilersforums.com/tanking-wetrooms/56943-getting-my-wet-room-project-back.html


Any advice & guidance would be much appreciated.



Thanks again....

 

[Stewart]

The silicone I use for the ply is the cheapest I can get, as it's only purpose is to sop the gap being filled with adhesive.....


Created on iPhone.....

 

[ojtiler]

Stewart - thanks for the follow-up. That's good to know; I have a couple of tubes of Silicone in my garage which will do nicely, so I'm good to go!