Tiling on floor boards & shower tray sealant

[Jammy]

Hi all, this is my first post

I’ve been browsing the forum for advice before I do a tiling job on my ensuite. So far I have purchased a Rubi Star N 60 plus tile cutter and tile drills as recommended by forum members.

OK so the ensuite is upstairs the floor is 18mm thick tongue and groove in good condition – house was built in 1996. I’ll be tiling the floor and walls (porcelain 600 x 300 walls and 400 x 400 floor), and underfloor heating. Room is 3.5m by 2.5m (there are 10 joists in the 3.5m length). I’ve been searching the forums and it seems I need to WBP ply at least 10mm thick on top of the floorboards. If I do this, do I also need the underfloor insulation panels as these are another 10mm. Then adhesive 3mm and tiles 8mm. I don’t really want the floor to be 31mm higher than the adjacent bedroom.

So can I leave out the insulation boards or will this render the underfloor heating too slow to warm-up ?

I’m also in the process of installing a 1400 x 900 JT40 shower tray (in a recess i.e. it has 3 walls) and I’m worried about getting a good seal between the tray and the 3 walls. Can anyone recommend a good quality sealant anti mould flexible etc. I’ve read a thicker sealant bead is better than a thinner one as it has more chance of expanding.

Thanks in advance :8:

 

[jay]

HI DONT FORGET TO TANK (WETDECK) :8::welcome:

 

[Jammy]

jay

I wasn't planning on tanking anything, as it is not a walk-in shower or wet room.

I'm planning on cementing the shower tray to the floorboards as per JT40 installation instructions. The tray will be butted up on 3 of it's sides against aquapanel walls (to form a recess) and the 4th side will be partitioned off with 1400 mm shower screen. Thus the floor outside of the shower recess shouldn't be getting wet.

I'll then tile against the aquapanel walls leaving a small gap between the bottom edge of the tiles and the top face of the shower tray. Then seal the gap with some good quality sealant that I'm hoping forum members will recommend.

Do I still need to tank anything ?

 

[Olz]

Not really mate unless you want to go belt and braces to be honest, the aqua panel wont break down under water, it just isnt water proof so will absorb the water which can lead to it passing into whatever is behind the aqua panel, tanking makes it waterproof so the water wont pass through.

If there is no deflection (bounce) in the floor then I would overboard with 6mm cement panel then UFH ontop of that and self level over the cables. Then tile, the insulation or lack of it wont cause the UFH to be ineffecting, its more important when the subfloor is concrete as this takes along time to warm up and absorbs the heat.

Hope that helps

PS if you havent already done so check out our sponsor Underfloor Heating | Electric | Floor Insulation | Uheat

There kits are excellent and very well priced.

 

[Jammy]

Thanks Oli that does help. I was thinking the same UFH on a wooden floor is not the same as trying to warm-up a concrete floor.

So basically since the original floorboards are sound i.e. no bounce I can get away with overboarding with 6mm cement board and no UFH insulation boards. This will keep the floor height down excellent nicely :8:.

I did have a tiler round to do our bathroom floor a few years back (no UFH on that one - and it is cold). I know he didn't overboard it, but he did put down some sort of matting (not sure what) then tiled on top. Floor height did not seem to rise at all - and non of the tiles or grout have cracked.

Cheers :hurray:

 

[Olz]

Probably Ditra matting which is an uncoupling membrane for lateral movement NOT deflection, its doesnt strenghten the floor.

If the boards and sound with no deflection 6mm cement board will be fine.

 

[Andy Tiler]

Hi jammy if your floor is sound and you are useing ufh i would go for a 6mm thermal board.the cement board will soak up the heat.the thermal board will reflect the heat.before you stick the boards down make sure you screw down the exhisting t/g floor.get in touch with u heat on this forum

 

[Jammy]

andy tiler

thanks for the advice, although I thought the suggestion for 6mm cement board was to provide some structural strengthening of the floor. Presumably the 6mm thermal board is no good for strengthening but like you said very good at reflecting the heat.

This is my confusion do I need both i.e. overboarding and thermal insulation.

I'll take a look at the UFH forum.

cheers

 

[Andy Tiler]

Hi jammy 6mm or 12mm cement boards add no strength to timber floors. these boards only provide a good key for the adhesive. a 6mm cement faced insulation board will be fine for the job providing your tg floor is rigid. and i would advise you to use a 2 part adhesive.ie weber.set wf21 or bal single part fastflex hope this helps

 

[Jammy]

Thanks andy,

Right That settles it then. I'll be going for the thermal boards. Luckly the shop where I purchased the tiles and adhesive from were very helpful, they also recommended bal single part fast flex.

Cheers

 

[iaincameron]

Jammy,

I was going to use Bal SPF, but following advice here I have ended up with Mapei Keraflex Maxi. I have floorboards, 12mm ply, wired underfloor heating which will have SLC over it (3-4mm) and then Keraflex Maxi and tiles.

The main reason for using the Mapei stuff was cost. Less than £14 (inc VAT) for a 20kg bag (white) from CTD in Warrington as opposed to £32 + VAT for Bal.

Cheers
Iain

 

[kingk]

alrite jimmy
trustilng kev

 

[Jammy]

Jammy,

I was going to use Bal SPF, but following advice here I have ended up with Mapei Keraflex Maxi. I have floorboards, 12mm ply, wired underfloor heating which will have SLC over it (3-4mm) and then Keraflex Maxi and tiles.

The main reason for using the Mapei stuff was cost. Less than £14 (inc VAT) for a 20kg bag (white) from CTD in Warrington as opposed to £32 + VAT for Bal.

Cheers
Iain

Iain thanks for your reply,

So you went for 12mm ply on top of floorboards but no thermal board on top of the PLY. Are you happy with the performance of the UHF i.e. does it warm-up quick enough ?. Were your floorboards in good condition or did they "bounce" which is why you went for ply.

I must admit I'm still not sure what I will do in my case, I was looking at WBP ply tonight in B&Q various thickness available 6, 9, 12, & 18mm. 6 looked a bit flimsy wereas 18 looked way too thick for my small room.

With regard to the adhesive looks like there are good deals available on the Mapei products, I went for Bal as it was available from the shop were I got the tiles from (don't know if they also do Mapei) and I didn't check all the advice from this forum first. However I got a really good deal on the tiles, the price tag on the tile display was £43 per m (and I needed 31 square meters walls and floor) but after some negotion they reduced them to £19 per m :hurray:. The Bal SPF though cost me £35.56 for 12.5Kg excl VAT .

 

[iaincameron]

I've not got the floor down, so can't comment yet! The floorboards were fairly good (70's house), but I screwed down any bouncing ones first before the ply. The shower tray was also mounted on the ply and I didn't want that straight on floorboards so I had to overboard. We have UFH in the kitchen which was straight on concrete (not by me!) and it does seem to use quite a lot of power!

As far as ply goes Wickes is a LOT cheaper than B&Q and also does bigger sheets. If I was you I would take that Bal back to the shop at that price. You will need 2 or 3 bags I would guess, especially if covering UFH without using a SLC. No doubt one of the proper tilers, rather than a DIYer, can advise how much adhesive you will need.

 

[Jammy]

Iain
Thanks for the advice, I'll take a look and consider SLC.