HI Folks

I'm installing a low-profile shower tray - one of the 'resin' types
(referred to in the instructions as 'Not-Easy-Plumb', as opposed to
'Easy-Plumb...)


Anyway, it's going to sit on top of a piece of 18mm ply, supported on
4"x2" timber - all arranged to get the top of the ply level...

The instructions insist that, even if you're sitting the tray on a flat
surface (like the ply) you still need to bed the whole thing on a
troweled layer of 'fine sand, cement and an anti-crumbling agent
(Unibond/pva), before sitting the tray on the wet cement 'ensuring it is
fully supported'.

The underside of the tray looks as if it has already been ground off
'flush' - so why the need for an additional thickness of sand & cement ?

My initial instinct would be to use some sort of mastic - but the
instructions go on to say 'Silicone sealants, foams, mastics or similar
must not be used to substitute for cement'....

Any idea why this should be so - or whether flexible tile cement (which
I have in abundance!) would be an acceptable substitute for the
sand/cement mix ?

Thanks
Adrian

On Wed, 04 Feb 2009 09:15:41 +0000, Adrian
wrote:


The underside of the tray looks as if it has already been ground off
'flush' - so why the need for an additional thickness of sand & cement ?


I can't answer the question but for the last five years my shower tray
has been sat on a bed of tile adhesive without any problems; I assume
that the fitters got into the habit of using because it was to hand.

On Wed, 04 Feb 2009 09:15:41 +0000, Adrian wrote:

HI Folks

I'm installing a low-profile shower tray - one of the 'resin' types
(referred to in the instructions as 'Not-Easy-Plumb', as opposed to
'Easy-Plumb...)


Anyway, it's going to sit on top of a piece of 18mm ply, supported on
4"x2" timber - all arranged to get the top of the ply level...

No you want to get the top of the tray as installed level. IME the trays
are not level within themselves. Especially at the commodity end of the
market.



The instructions insist that, even if you're sitting the tray on a flat
surface (like the ply) you still need to bed the whole thing on a
troweled layer of 'fine sand, cement and an anti-crumbling agent
(Unibond/pva), before sitting the tray on the wet cement 'ensuring it is
fully supported'.

The underside of the tray looks as if it has already been ground off
'flush' - so why the need for an additional thickness of sand & cement ?

Arse armour IMHO.
A reasonably thick bead of silicone/stix-all/CT1 should do the same and
be less messy.


My initial instinct would be to use some sort of mastic - but the
instructions go on to say 'Silicone sealants, foams, mastics or similar
must not be used to substitute for cement'....

Even I'm beginning to get a little worried. The reality is that a well
constructed base bedded with some gunk to spread the load and I'd risk it.
The tray is unlikely to break if it does they have made things as hard as
possible to make a claim. The real cost won't be the tray anyway but the
dismantling and refitting of the enclosure etc. I bet that's not covered
anyway.

My 2p worth 0p



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

HI Peter

Peter Johnson wrote:
On Wed, 04 Feb 2009 09:15:41 +0000, Adrian
wrote:


The underside of the tray looks as if it has already been ground off
'flush' - so why the need for an additional thickness of sand & cement ?


I can't answer the question but for the last five years my shower tray
has been sat on a bed of tile adhesive without any problems; I assume
that the fitters got into the habit of using because it was to hand.

Ah - that's interesting g - thanks

See also my reply to Ed

Adrian

HI Ed

Ed Sirett wrote:
On Wed, 04 Feb 2009 09:15:41 +0000, Adrian wrote:

HI Folks

I'm installing a low-profile shower tray - one of the 'resin' types
(referred to in the instructions as 'Not-Easy-Plumb', as opposed to
'Easy-Plumb...)


Anyway, it's going to sit on top of a piece of 18mm ply, supported on
4"x2" timber - all arranged to get the top of the ply level...

No you want to get the top of the tray as installed level. IME the trays
are not level within themselves. Especially at the commodity end of the
market.

Fairy 'nuff....

I have to adjust the levels anyway - as the new shower tray is being
installed to sort out the existing cock-up of an attempts at a built-in
shower/wet-room thingy with a (semi)-sloping floor - so there's room for
a bit of adjustment with the timber so as to end up with the right level
on the top of the tray.....



The instructions insist that, even if you're sitting the tray on a flat
surface (like the ply) you still need to bed the whole thing on a
troweled layer of 'fine sand, cement and an anti-crumbling agent
(Unibond/pva), before sitting the tray on the wet cement 'ensuring it is
fully supported'.

The underside of the tray looks as if it has already been ground off
'flush' - so why the need for an additional thickness of sand & cement ?

Arse armour IMHO.
A reasonably thick bead of silicone/stix-all/CT1 should do the same and
be less messy.

Well - that's what I thought...
and even had a couple of emails back & forth with the manufacturer's
tech support people (very responsive, actually)..

I suggested that a combed bed of tile adhesive would (might!) be
suitable instead of sand & cement...

They said ...

quote ----
I am unable to confirm if you particular adhesive is sufficient for the
purpose. However, I would strongly recommend the use of an adhesive
based on Portland cement or cement in general.

I would also strongly recommend an even screed of material over the
total surface area and NOT the use of a notched spreader, as this has
been shown to form high spots for the tray to belly out on when and if
the material should cure too quickly during installation.
---unquote

Does sound a bit like backside-covering, to me....


My initial instinct would be to use some sort of mastic - but the
instructions go on to say 'Silicone sealants, foams, mastics or similar
must not be used to substitute for cement'....

Even I'm beginning to get a little worried. The reality is that a well
constructed base bedded with some gunk to spread the load and I'd risk it.
The tray is unlikely to break if it does they have made things as hard as
possible to make a claim. The real cost won't be the tray anyway but the
dismantling and refitting of the enclosure etc. I bet that's not covered
anyway.

Probably not g

Despite all the dire warnings, I'm leaning towards combed tile cement -
after first having got the timber structure set up to achieve 'level' on
the top of the tray...


My 2p worth 0p

Not at all - very helpful - and kind of reassuring...
This is the first of these 'resin' trays I've fitted - always used
the old-fashioned ones before - foamed core and acrylic top surface.

I'll give it a try with tile adhesive - once my timber turns up
(this unusually cold weather's a gift for suppliers out here on the
edges of the civilised world - currently waiting for four seperate
deliveries of materials... and want to get on with things !! g

Thanks
Adrian

HI Ed

Ed Sirett wrote:
On Wed, 04 Feb 2009 09:15:41 +0000, Adrian wrote:

HI Folks

I'm installing a low-profile shower tray - one of the 'resin' types
(referred to in the instructions as 'Not-Easy-Plumb', as opposed to
'Easy-Plumb...)


Anyway, it's going to sit on top of a piece of 18mm ply, supported on
4"x2" timber - all arranged to get the top of the ply level...

No you want to get the top of the tray as installed level. IME the trays
are not level within themselves. Especially at the commodity end of the
market.

Fairy 'nuff....

I have to adjust the levels anyway - as the new shower tray is being
installed to sort out the existing cock-up of an attempts at a built-in
shower/wet-room thingy with a (semi)-sloping floor - so there's room for
a bit of adjustment with the timber so as to end up with the right level
on the top of the tray.....



The instructions insist that, even if you're sitting the tray on a flat
surface (like the ply) you still need to bed the whole thing on a
troweled layer of 'fine sand, cement and an anti-crumbling agent
(Unibond/pva), before sitting the tray on the wet cement 'ensuring it is
fully supported'.

The underside of the tray looks as if it has already been ground off
'flush' - so why the need for an additional thickness of sand & cement ?

Arse armour IMHO.
A reasonably thick bead of silicone/stix-all/CT1 should do the same and
be less messy.

Well - that's what I thought...
and even had a couple of emails back & forth with the manufacturer's
tech support people (very responsive, actually)..

I suggested that a combed bed of tile adhesive would (might!) be
suitable instead of sand & cement...

They said ...

quote ----
I am unable to confirm if you particular adhesive is sufficient for the
purpose. However, I would strongly recommend the use of an adhesive
based on Portland cement or cement in general.

I would also strongly recommend an even screed of material over the
total surface area and NOT the use of a notched spreader, as this has
been shown to form high spots for the tray to belly out on when and if
the material should cure too quickly during installation.
---unquote

Does sound a bit like backside-covering, to me....


My initial instinct would be to use some sort of mastic - but the
instructions go on to say 'Silicone sealants, foams, mastics or similar
must not be used to substitute for cement'....

Even I'm beginning to get a little worried. The reality is that a well
constructed base bedded with some gunk to spread the load and I'd risk it.
The tray is unlikely to break if it does they have made things as hard as
possible to make a claim. The real cost won't be the tray anyway but the
dismantling and refitting of the enclosure etc. I bet that's not covered
anyway.

Probably not g

Despite all the dire warnings, I'm leaning towards combed tile cement -
after first having got the timber structure set up to achieve 'level' on
the top of the tray...


My 2p worth 0p

Not at all - very helpful - and kind of reassuring...
This is the first of these 'resin' trays I've fitted - always used
the old-fashioned ones before - foamed core and acrylic top surface.

I'll give it a try with tile adhesive - once my timber turns up
(this unusually cold weather's a gift for suppliers out here on the
edges of the civilised world - currently waiting for four seperate
deliveries of materials... and want to get on with things !! g

Thanks
Adrian