Flooring advice and preparation of timber floor.

[moodym]

Hi All,

im after some advice on flooring if i may. What i am planning on doing is removing the floorboards in a bathroom, batten between the joists and then infill with plywood. Then, install 20mm of Jackoboard (xps insulated board) over the top with flexible tile adhesive and mechanical fix. once in place i will install the UFH. The UFH is loose wire which sits in a purpose made plastic decouping mat which will be stuck down with flexible tile adhesive. i will then tile over the top.

My question is do you think the 20mm insulation board straight down on top of the joists (which is infilled with ply) will be sturdy enough for the tiles?

i decided on this approach to keep the floor buildup low, and have as much insulation as i can get away with....

another option i was thinking about was to go straight over the joists (again infilled with ply) with 'No More Ply' 6mm boards.. these, i am told are as study as 15mm ply.... then on top of the 'NMP' stick down 12.5 mm of Jackoboard....

Which option do you think would be best?

any help advice would be appreciated..

 

[Boggs]

I wouldn’t consider doing either of those myself.

Why not overboard the existing floor, if you have a new carpet and 10mm plus underlay on the adjoining room the finished floors usually end up almost the same.

Otherwise have a look at 22mm No More Ply and lay this over the joists, not cheap but would be the very best for tiling over.
What you would loose in warmup time you will gain in heat retention.

 

[moodym]

i probably should of mentioned this will be a wetroom, so i will have a insulation board shower tray in the corner. this will be 20 mm on top of joists. i can go higher outside of the tray to aid the fall but didnt fancy tanking the room over NMP. i also thought NMP or hardie board did not have as good heat retention as the insulation board...

 

[Steve6690]

Have you allowed for the height of the UFH system? 20mm tray and 20mm floor height plus UFH will make your floor higher than the tray.

 

[Deleted member 54066]

Assuming you don't heat the tray!
I do.

 

[Steve6690]

He didn't specify so I thought I'd just drop the hint.

 

[moodym]

i was not intending on heating the tray to be honest. the tray i am thinking of buying is 20mm. so ideally i need to build the rest of the floor to the same height.. i was under the impression i could tile on top of 20mm jackoboard. yes i would have another 5mm of UFH which i would not have on the tray, but the tray needs a fall anyway, so... it would be a bit more of a fall... i guess i am concerned about the sturdiness of the jackoboard...

the floor in the bedroom is on 18mm chipboard, so this plus UL plus carpet would be about 40mm.

ultimately need advice on how to construct the floor for insulation and UFH so i can tile the wetroom... with as near to the bedroom finished floor as possible...

thanks all for your help.

 

[Steve6690]

You could put some 5mm Jackoboard under the tray to bring it up to the same height as the surrounding floor.
I actually don't see anything wrong with your first suggestion - plywood on noggins between the joists. It's how Schluter teach you to support their foam trays so it should be good enough for the rest of the floor. It's a lot of work though.

 

[moodym]

Thanks Steve and all for your replies... im going to go with the 20mm jacko on the floor. i have already infilled between the joists as i had nothing else to do (during this time)... and will lift the tray with 5mm jacko as Steve suggested...

 

[Perfect Tiling]

I wouldn't worry too much about lifting the tray 5mm. the fall in the tray kicks the tiles up anyway so they'll meet the floor tiles. Also, you usually put more adhesive under a tray to keep it solid as its only held down with the adhesive.......the floorboards are usually held down with screws and washers and the adhesive just fills any voids.