fitting a resin stone shower tray

[talisker]

i've got a mira resin stone shower tray that i need to fit it's a long one at 1500mm the floor is wood and is approx 3 or 4 mm out at one end, i was wonder what would be the best method for bedding it down the instructions say use silicon or a floor screed, can any one recomend somthing i could use

 

[stuart45]

I used a mix of lime and silver sand to bed mine. I was advised to avoid using a tile adhesive as the tray could crack in time with this.

 

[Blasphemous]

Whatever way you decide to bed it in, you should follow the Manufactures Instructions (MI's), otherwise they'll reject any subsequent claim. If you haven't got the MIs ask the company you purchased it from to advise you... ie put the ball in their court. If it goes wrong, they advised you!

I prefer/I'm more comfortable with, first fixing a Marine Ply Board and then bed it in with mortar. But as I say, follow the MI's or you could live to regret it.

 

[talisker]

i've used marine ply for the base but the last foot is the old floor that is the part that is slightly uneven the maufactures instuctions just says use a suitable floor screed or silicon.

 

[Richard C]

I find a weak mix mortar on a suitable base much easier to work with but whatever you use the base must be fully supported; stone resin trays are basically concrete with a thin resin covering so are quiet brittle. Mix it stiff & you'll make up 2-4mm easy.

 

[talisker]

i contacted mira today and they said as it's a big shower tray (1500x760) that it would be best to use sand and cement at a 5 to 1 ratio as it's a large area to do with silicon.
this is on to a wooden floor floor is this ok ?
my other problem is the shower tray is being fitted into the corner of a small room so there are walls on all 3 sides of the shower tray making it difficult to lower down evenly, is it best to put the sand and cement mix down evenly covering the whole area or just put blobs down every few inches, i'm just a bit worried about getting it right as once it's down it will be difficult to do anything with it if it's not right, sorry for all the questions

 

[Richard C]

What do you mean by a wooden floor; hope it’s not chipboard? The mortar mix must be a continuous bed laid onto the floor otherwise you could end up with voids which may cause the tray to crack. Lay & level the bed first & it may pay you to lower the tray down from the highest to the lowest point but its heavy & as long as it’s not a precision fit between the walls, once it’s down you can tamp & wiggle it until you get your levels correct; I’ve never had any problems even with 3 closed sides.

 

[talisker]

unfortunately part of the floor is chipboard that green stuff that is meant to be water resistant, i did replace most of the floor with marine ply but the last 18" of floor i had to leave as the last floor joist was under the stud wall.

 

[Blasphemous]

EDIT: I see the reason for the 'old floor' bit now.

You say you've got Marine Ply in place but then you mentioned something about the last foot being the 'old floor'. Why can't you run the Marine Ply right through? I also notice you say that the old floor is 'slightly uneven'. If you use a decent cement base then it will take up any irregularities in the floor but my concern is with the 'old floor' material. Is this ordinary floor boards or worse still, chipboard flooring? If it's chipboard then that could end up causing you a huge problem if it starts getting wet on a regular basis. If it's floor boards then you need to be VERY careful with regard to any flex they may have. If you cannot run the marine Ply right through for some reason and the 'old floor' is boards, then personally I'd try and get access to beneath them and provide extra support by screwing decent sized timbers to the floor joists. You could cut a piece of Marine Ply to size and fix that to the underside of the floor boards then fix timbers to the joists. It my sound like over kill and indeed it may be but we cannot see the job and if there is flex in the floor then as Richard C has said, if the base is not fully supported you may end up standing in the tray and.... SNAP! A few photos might help. Especially of that 'old floor' bit.

 

[talisker]

the floor feels solid even the last bit that is chipboard, i'll take a picture of it tomorrow it's always difficult to try and explain and for people to see what you are getting at without seeing the job

 

[talisker]

hope it works, here is a picture of the floor as you can see the last bit is chipboard the floor feels solid enough so hopefully will be ok
it's a tight space so will be awkward to lower the tray evenly onto the floor ,also do i have to use enough cement mix that it goes into the channel that runs around the edge of the base, this is the base i'm using.

thanks again

http://www.mirashowers.com/onlinecatalog/tray_flightlow.jsp

Untitled

• talisker
• 19 Feb 2009
• 1

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[Richard C]

That looks like a lump of old Sapele door or part of your grannies old headboard no wonder you’ve got a 4mm run out! I wouldn’t bed a stone resin tray on that; do it properly, take it & the crapboard up & replace it with a full size WBP ply base board.

 

[Symptoms]

tali - I'm with RichardC on this one - spend a bit of time taking that bit of ply up AND AND AND that bit of chipboard which'll be under the tray (at least). What you should really do is to remove ALL the chipboard in the room and sheet with exterior grade ply (at least 18mm thick WBP). What are you going to finish the floor outside the tray's footprint with? Tiles? Even more reason to bin the chipboard. Leave the chipboard and you WILL live to regret it.

It doesn't matter that one of the wall sits on that bit of c/board; remove by sawing/chiselling as much as possible away, then reinforce the structural timbers by 'sistering' the joists and adding noggins (sistering is where you glue/screw additional timber {say studding or similar} along the joists. By doing this the edge of your new ply floor will rest, and be fixed, to structure. Doing this will be time well spent, maybe ½ a day!

Mortar mix can happily go on the WPB ply and only needs to interface with the tray edges and base - you don't need to fill-up that "channel". The aim is to provide support directly below where the load will be.

Tip: how to successfully lower the heavy tray onto the mortar bed without dislodging or disturbing the mortar. Use 2 lengths of nylon cord looped around the tray (one at each end) to form lowering handles - this will guarantee the thing goes down flat. When you're down undo the knots on the rope and pull them gently free. If you're big and strong with a back in decent condition you could do this yourself, otherwise rope-in (sorry for that pun) an able assistant ... maybe Mrs Talisker.

 

[talisker]

hey, that was my grannies best headboard
ok i accept that it's a crap job i just thought it would be better than sistering the joists but i guess you guys are right it's a job i only want to be doing once so i want to get it right, i'll order some WPB ply on monday and replace the whole floor it's an ensuite so it's not a large area.
what about the mortar mix does 5 to 1 seem right ?
thanks again for your help.

regards dave

 

[Blasphemous]

Dave,

Good decision regarding the floor! As I stated yesterday and Symptoms stated earlier, you would have lived to regret leaving Chipboard in place.

Just one other point, have you considered access for plumbing in the Shower Tray Waste? I don't know how/if you were considering access before but you could leave yourself a nice access hole which can be screwed into place once you've plumbed in the waste.