Shower Tray Installation Onto Sand / Cement

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All,

I have created a timber 4 X 2 plinth to put my quadrant (1000 x 800) stone resin shower tray on. I have 18mm WBP ply on the top.

The manufacturer's instructions say to bed the tray into a sand and cement mix. I have a couple of questions regarding the best way to install this tray.

1) Should I treat the 18mm ply with PVA before I put my sand and cement mix on it? I seem to read conflicting stories on the use of PVA. Would it prevent the sand and cement mix adhering to the ply correctly? I've also read that PVA should be added to the mortar mix?

2) The stone resin tray is amazingly heavy and I have been trying to think how the best way of getting this tray on to the plinth once I have the sand and cement mix down. There is no obvious way I can think to lower the tray down vertically onto the platform (so as not to move the sand and cement mix) as there is little way of supporting the tray physically. If I get it 3/4 on and then slide it, it will just move all the sand and cement underneath. Has anyone any good recommendations for the best way to lower it down onto the plinth?

Thanks in advance,

Daz
 
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It doesn't have to sit on a bed of sand and cement, but that is a convenient way to evenly support the tray and still allow enough movement to level it properly. There are other ways. In a pinch you can just sit it on the wood but you risk it moving, not being level, or occasionally warping or splitting.

Don't panic about the cement adhering to the wood, it isn't structural. You can mix PVA into the cement which will make it more plastic.

Can you place the tray on the support at angle (front down, back raised) and then lower it down within an inch or so of the wall? Sliding across the cement a little won't hurt. Ideally you do this before finishing the tiling so it doesn't have to butt right against the wall. Depending on how your plinth is constructed, can you place the tray on the plinth and then move the whole thing into position?
 
D

DeltaT

Don't be overly concerned Daz, the mortar mix will be fine directly on top of the plywood. Forget PVA, we've never used it & not known a tray fail or become unstuck.

As for the weight, lay a good bed onto the ply 10-15mm thick, get a pal to help you lift it & plonk it onto the cement bed. Level it, that's very important! Also, ensure you can connect the shower tray trap easily.

I don't give free advice, so please pop a few bob in a kids charity box - the next time you pass one. I was lucky, I had parents that cared & loved me. Unfortunately, many kids in this country live in hell, so don't forget the 'honesty' box.......... ;)
Thanks.
 
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It doesn't have to sit on a bed of sand and cement, but that is a convenient way to evenly support the tray and still allow enough movement to level it properly. There are other ways. In a pinch you can just sit it on the wood but you risk it moving, not being level, or occasionally warping or splitting.

No I realise there are other methods other than on mortar but I am going to fit mine according to the manufacturer's instructions. They say sand and cement, so that's what I am going to use. Then if there is any fault that occurs through a manufacturing fault then I am "on concrete" (so to speak :D)

Don't panic about the cement adhering to the wood, it isn't structural. You can mix PVA into the cement which will make it more plastic.

Thanks I'll do this when I mix my mortar up.

Can you place the tray on the support at angle (front down, back raised) and then lower it down within an inch or so of the wall? Sliding across the cement a little won't hurt. Ideally you do this before finishing the tiling so it doesn't have to butt right against the wall. Depending on how your plinth is constructed, can you place the tray on the plinth and then move the whole thing into position?

I think I'll have to go with trying to angle and lower it down. My plinth is actually already screwed down to the floor and to the wall. Maybe, I should have left it free, installed the tray and then manoevered the whole thing against the wall as you've suggested. I did think the same after I'd screwed it down! Doh!

Thanks for the reply.
 
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The purpose of the mortar mix is to support the tray evenly rather than stick it down. Once the tray is bedded in the mix, gravity will stop it going anywhere.

You could lay a couple of battens or slater's laths on the bedding mortar to slide the tray into position, then pull the the laths out before levelling it.

IMO A movable plinth would be self - defeating. You may have your tray nicely supported and levelled on the plinth,but then you would have the problem of how to fix and level your plinth on the floor.
 
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personally i use a thick mix of quick set floor tile adhesive, the tray should have a lip where it wont touch the wood ( like a 2x2 cavity) the two edges where the wall are dont need adhesive on as the tray wont be touching it, so leave them clean, put the tray on there put your adhesive on the base then lower it down, u shud have ur base fairly level to strt with mind you. n make sure waste is in right pos as she doesnt like comin bk up again
 
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I have just read this post as I am about to embark on the same task, assisted by my father. i hope the job went well for DazJwood, and I realise his post was last year, but in case someone else like me is reading this in 2011 I thought I would post what I have decided to do. I plan use two 30mm wide webbing roofrack straps passed under the tray that my father and I can use to lower the tray carefully onto the mortar. Once gently placed on we can hopefully slide the straps out leaving a 1-2mm trail in the mortar which will disappear when I bed the tray down. I am not sure yet how the excess will complicate things when it squishes out from the edges, as it may be difficult to remove. I must admit that after a total rennovation of the bathroom which has included removing ceilings and moving doors, plumbing and plastering, in an obstinate 1930 house that has seen a number of home DIYers do their thing, this is the last 'big' job that is keeping me awake at nights. I will be glad when it is done !. Thanks to everyone who has posted previously. I will be putting some money in an honesty box.
 
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SpencerFrank,

I mixed a mortar mix (sand and cement) and intially tried the ice cube trick but realised it wasn't necessary. With the help of a friend we lowered it in as close to the wall as possible and then pushed it up against the wall and bedded it down. It is now rock solid in the right position. I filled the slight gap between wall and tray with silicon and tiled down. I tanked my walls with membrane down and overlapped the top of the tray. My tiles are thick travertine tiles (13mm thick) these overlap the tray nicely and then another line of silicon on tile to tray.

Daz
 
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I am about to install a 1200 x 800 quadrant tray on to an 18mm marine ply base, the tray instructions say to use a sand and cement mix, then add some PVA to the mix, this is all well and good but no where does it give the ratios.
Does anyone know, it can't be a secret even though I have spent ages trying to find an answer. :rolleyes:
 

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