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floor under shower tray

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comp.zrch.embedded

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Oct 13, 2010, 11:21:18 AM10/13/10
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I am replacing a shower tray (1200mm x 800mm) with a new low profile
25mm high tray. The new tray recommends the floor should be 18mm
marine ply. The current floor is 18mm chipboard and since some walls
sit on top of this if I replace this floor with 18mm ply then the ends
of the ply (200mm) will overhang the floor joists and would therefore
seem to me to be more flexible than the current floor. This is a inset
tray so has plasterboard walls on 3 sides so the ply will have to be
exactly the same size as the shower tray. The current shower tray was
raised up on 4x2 with 18mm chipboard on top for easy drainage but I
have got round this drainage issue and need it as low as possible What
do people think I should do as I am not sure how much difference there
is in flexibility between the two materials

Thanks

Jim K

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Oct 13, 2010, 11:31:55 AM10/13/10
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i have amost exact same issue...

i plan to add more timber joists (at 90deg to the existing) in the
area under the tray to eliminate *any* flexing of the new ply floor
under the tray (as that flexing of the floor will definitely cause
cracks/leaks etc later and all have to be done again)...

the extra joists will also add support to the stud walls that are
built on top of the chipboard floor.

It means taking up parts of the floor in the adjacent room to be able
to fix the new timbers but worth it IMHO..

Jim K

harry

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Oct 13, 2010, 11:45:00 AM10/13/10
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On 13 Oct, 16:21, "comp.zrch.embedded" <sjo...@scannex.co.uk> wrote:

You could paint the existing floor and then put down thick polythene
sheet.

comp.zrch.embedded

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Oct 14, 2010, 5:24:30 AM10/14/10
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Do you think 18mm MDF would be ok, appropriately treated, as I have a
sheet of it
Thanks

comp.zrch.embedded

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Oct 14, 2010, 5:26:38 AM10/14/10
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Manufacturer of my shower tray (1200mmx800mm on suspended floor)
recommends replacing the floor with 18mm Marine ply. I have 18mm MDF
would this be ok, appropriately treated, as I have a sheet of it
Thanks

Jim K

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Oct 14, 2010, 5:52:11 AM10/14/10
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mmm MDF is also susceptible to water/damp damage - what is this
"appropriate treatment"?

for the sake of £25 on plywood is it worth it? only you can answer
that one.

Jim K

comp.zrch.embedded

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Oct 14, 2010, 8:11:28 AM10/14/10
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Thanks, have brought the ply and will add joist braces etc where it
overhangs joists
Thanks again

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