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MAB

CT1 and/or Sikaflex for a shower tray installation?

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I have read on the BuildHub forum both CT1 and Sikaflex is often recommended instead of using conventional Silicone sealants when installing a shower tray.

I am about to install a Zamori 1700 x 800 walk-in tray (Acrylic steel framed) with a fixed glass panel but am unsure whether I should use both CT1 & Silkaflex and if so where is each best suited to do the job best?

http://www.zamori.co.uk/Features

 

I was recommended the Zamori Acrylic tray below by a local plumber as it has a steel frame, a 10 year guarantee and is not as heavy to install as some other large trays.

The tray will be sitting on 18mm ply screwed to the floor joists and bedded on flexible tile adhesive, walls are to be lined with HardieBacker cement board (on batterns) down to the floor (1st sealant between wall and tray) and will be tiled onto the tray (2nd line of sealant between tiles and tray).

Walk in rectangular 1700 x 800 x 35mm tray:-

http://www.zamori.co.uk/Products/ProductDetail?prodId=81021&name=Walk-In 1700 x 800 shower tray anti-bacterial

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@MAB

Sorry, I missed this somehow. 

If using tile adhesive, you need to be very sure there are no contaminants from manufacture on the underside. I've had a few which have some slimy stuff ( a mould release agent of sorts I suspect ) and nothing will stick to that.

I'd use Sikaflex between the tray and the backerboard, applied whilst bedding the tray into the tile adhesive. Use that to create the fundamental seal between the tray and wall, and then tool the displaced sealant onto the BB to create an upstand seal ( have you read my comments in the tanking / wetroom thread )?

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Thanks Nick for clarifying where to use the Sikaflex and create an upstand seal. I will use the CT1 for the tile to tray joint, in corners and for bedding the glass side panel onto as explained in some of your other threads.

I will also check the underside of tray for any release agent and clean off as you suggest, many thanks for the tip.

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@MAB just wondering how you got on with this?

I'm about to install my tray and the instructions say to use a weak mortar mix for bedding it down. However given the potential for movement (suspended floor with a 16ft span, so there is a little bit of bounce) I'm inclined to go for something more flexible- and preferably something 'stickier'.

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17 hours ago, Woodgnome said:

What Sikaflex do you use?

Seems to be a variety of different ones.

I use EBT mostly, and yes there are a load of different types available. 

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As @Nickfromwales says, there are several different Sikaflex compounds.  Originally, Sikaflex was only a polyurethane, moisture curing, sealant/adhesive.  This was the stuff that earned Sikaflex a good reputation as a sealant that would tick like sh*t to a blanket, on damned near anything.  The two downsides with it were the slight smell and the fact that it was, if anything, too good an adhesive (damned near impossible to get off when cured).

 

Since then, several manufacturers have come up with other formulations, from polysulphide sealants (excellent stuff for sealing up the joints inside aircraft wing fuel tanks, but smells awful and I'd avoid it like the plague) to a wide range of modified silicone polymers and polyurethanes.  CT1, Evo Stik "Sticks like Sh*t" sealant and Unibond F|T101, are examples of MSP adhesive/sealants that are near-identical.  Sikaflex EBT is a polyurethane that seems very similar to their old 223 industrial grade stuff, marketed as a building adhesive/sealant.

 

In general, there's not much to choose between any of the MSP or polyurethane products.  All are significantly better in just about every respect to standard moisture curing acetoxy silicone sealants, although some of the better neutral cure silicone sealants perform almost as well as the MSP stuff, but there's not a big enough price differential to make it worth using them, IMHO.

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Also worth noting that Everbuild is part of the Sika group - if you look at the MSDS for some of the products they are identical. Makes you wonder why the Sika logo doubles the price ...

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1 hour ago, PeterW said:

Also worth noting that Everbuild is part of the Sika group - if you look at the MSDS for some of the products they are identical. Makes you wonder why the Sika logo doubles the price ...

 

I think that's probably down to the reputation Sika has, mainly from its widespread use in the boat industry.  Sikaflex has been the "go to" sealant for everything on boats for decades, and practically everything associated with boats seem to attract a fair mark up.  I always used to buy my boat stuff from the grotty fisherman's chandlers in Falmouth and Penryn, rather than in the upmarket "yachtie" places, where the same product would be half as much again.

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2 hours ago, PeterW said:

Also worth noting that Everbuild is part of the Sika group - if you look at the MSDS for some of the products they are identical. Makes you wonder why the Sika logo doubles the price ...

At between £5 and £7 I just don't want to have to study the label TBH. Buy a Sikaflex product and you know your getting the right stuff. 

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Like a few others on this thread I'm now about to put down my shower tray.  I have a few queries.

 

Going to use flexible floor tile adhesive - is there a preferred brand?

 

How deep a bed did you all put down?

 

I assume its a solid bed rather than the normal tiled trowel pattern?

 

How long before it can take any weight?

 

Cheers.

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Make sure you clean the underside as sometimes they're contaminated with mould release agent and then nothing will stick to it.

Make up a little dry sand / cement mix to use like an Ajax and scrub it in with a sponge. Do this directly before laying the tray.

Use a flexible tile adhesive to bond the tray down. Any recognised make will be fine, but I purposely avoid Unibond as I've had a couple of bad experiences with that make refusing to go off. Whatever your bonding to, make sure you prime it with a flexible primer not PVA. Ultra is what I normally use. First coat 75% water and leave to dry ( 1 hour usually ) then 50/50 directly before putting the tray down so your more or less bonding to wet primer. 

If your feeling brave use rapid set, if not use standard set so you've got at least 30mins to adjust it.

Lay with a 10 / 12mm notch trowel and stay about 50mm from where the seal of the trap hits the tray. The adhesive will squeeze over a bit leaving only an inch or so un-bonded which is fine as typically you'll not ever stand on / directly next to the waste anyhoo. 

If there is any serious undulation in the floor eg 0mm-6mm-0mm again then notch the underside of the tray as well. 

If no serious undulation then just notch the floor and 'butter' the underside of the tray, the idea being to bring two lots of wet adhesive together for a guaranteed full bond. 

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Fantastic @Nickfromwales.  Bit of undulation in the floor and surprisingly under the tray so I think  its best to butter under the tray as well.  Rather the tray be slightly higher off the floor than redo / on the piss.

 

Will see if I can get the ceilings skimmed first.

 

1st time putting a shower tray in - bit nervous if truth be told.

 

 

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1 hour ago, CC45 said:

Fantastic @Nickfromwales.  Bit of undulation in the floor and surprisingly under the tray so I think  its best to butter under the tray as well.  Rather the tray be slightly higher off the floor than redo / on the piss.

 

Will see if I can get the ceilings skimmed first.

 

1st time putting a shower tray in - bit nervous if truth be told.

 

 

Ground floor in screed or 1st floor on joists?

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1st floor on joists.  22mm boards that have been glued and screwed.  Fairly solid but will add a bit more timber underneath where the tray goes before putting it down.

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Just found my local BM (Otford Builders Merchants) does the CT1 range! :)

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1 hour ago, CC45 said:

1st floor on joists.  22mm boards that have been glued and screwed.  Fairly solid but will add a bit more timber underneath where the tray goes before putting it down.

Do you still have access from underneath ?

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yes, still access from below.  Waste screwed on after?

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4 hours ago, CC45 said:

yes, still access from below.  Waste screwed on after?

 

16 hours ago, CC45 said:

1st time putting a shower tray in - bit nervous if truth be told.

Deffo break it down into chunks if possible. Once set you can stand / kneel on the tray which makes life a LOT easier ;)

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cheers  Nick.  Need to get the ceilings skimmed first then its game on.

 

if @Onoff can get a move on then I need to just do it :D

 

 

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