Tiling across a cavity /close problem

[vice]

Hi. I've searched the forum for an idea but can't figure this.
I'm tiling over a cavity to a new window that's about to be put in down to floor level from an existing lintel. This is at the dpc on both sides of the cavity

To be level with the floor I have about 1cm thickness for something to bridge the cavity and support the tile. The height tolerance for the window also only gives me about 1cm.

I'm presuming the floor tiles of c 8mm thick can't cantilever themselves over the gap.
I don't want to risk it.

14 mm slate is getting too thick. So.
Could I use a floor tile to bridge the gap, mortared onto the dpc.
Would a floor tile be strong enough, to support a floor tile?

 

[oldbutnotdead]

You say you're bridging the cavity so you have something on the far side of the cavity to take some load? How wide is the cavity- 100mm?
Whatever you use you'd have to fix it down - if you've only got 10mm then your mortar sketch is unlikely to work. I'd be thinking 10mm ply (if you can get it) doubled or tripled over the cavity (so the double/triple pokes down into the cavity) and screwed through the dpc into the bricks/blocks. Still might be iffy...

 

[^woody^]

You need to fill the cavity, and not bodge it.

 

[vice]

You need to fill the cavity, and not bodge it.

Thanks. So dpm pocket filled with concrete? Was concerned about being a thermal bridge, but only 1.2m wide.

Bridging the cavity I meant across both inner and outer bricks.

 

[noseall]

Thanks. So dpm pocket filled with concrete?

Remove enough inner leaf masonry to leave you with enough depth for a chunk of celotex (if the rest of the floor is insulated) and say 100mm of screed mortar. Because you are tiling and not carpeting (think grippers) you could also add a 25mm upstand of insulation against the external masonry.

Bridging the cavity I meant across both inner and outer bricks.

Correct. You also need to line the trough with DPM prior to insulating and filling.​

 

[vice]

Hi. Rest of the floor is celotex onto block and beam, with some chipboard on top then ply. No screed.
Are you suggesting remove inner leaf down to block and beam them build up the same as the rest of the floor over the cavity?

Remove enough inner leaf masonry to leave you with enough depth for a chunk of celotex (if the rest of the floor is insulated) and say 100mm of screed mortar. Because you are tiling and not carpeting (think grippers) you could also add a 25mm upstand of insulation against the external masonry.

Correct. You also need to line the trough with DPM prior to insulating and filling.​

 

[^woody^]

There are some pictures of the threshold detail that you need posted previously. IIRC, noseall has posted some.

 

[vice]

Thanks. I'd seen this one
https://www.diynot.com/diy/media/floordetail2.95659/
There is no screed layer to my floor though.

Will a pocket not simply fall down into the cavity? Or should I build up from the base of the wall right up? .

 

[vice]

Any remarks on this plan please. OK?
1 Old celotex in the cavity leaving 100mm or so.
2 Remove high density bricks on block and beam
3 fill cavity over old celotex up to level of block and beam
4 dpm on top of fill and up side of outer leaf with overlap
5 upstand of celotex on out leaf
6 continuation of floor to outer leaf.

IMG_20180720_192815

• vice
• 20 Jul 2018

 

[noseall]

Or this.....

Floor Detail

• noseall
• 6 Jul 2015

I think you get the idea though.