How to "fill" cavity at a new external door, ready for tiling

[jweaver]

I have just had new bifolds fitted and because I want to tile right up to the door, I cut out what I thought was some some trim, so the tiler can get right up to the door.

Turned out, this "trim" covered the cavity, and I believe it is a "cavity closer", which I have mostly removed (rightly or wrongly).

The gap is between the inner and outer brick course, and I need to close this some way so the tiler can tile over it.

Its about 50mm wide and 150mm deep.. And I hoped I could just fill it with mortar or foam, but talking to a friend at the weekend, he has put the fear of god into me as he talking about breaching the cavity causing a whole world of problem..

I have attached some photos which I hope will explain better.

So what can I do here? He suggested lining the whole thing with DPC membrane and filling it with cement, effectively making a 'bag', but this is almost impossible to do as its only 50mm wide (max)...
What options do I have? What can I do about this gap/cavity?

 

[Deluks]

Basically do what he said.
If you can get some thin insulation board (insulated tile backer board) and slot that in, even better.

 

[jweaver]

Basically do what he said.
If you can get some thin insulation board (insulated tile backer board) and slot that in, even better.

I did consider this, but the cavity is far from straight and is different depths, so it will be hard, if not impossible to get insulation board in.. Perhaps I could put it in in smaller pieces, but it didn't seem like a stable surface to tile over.. That said, its only the last 2" upto the door and I can't imagine anyone would ever step on it..

I was hoping to do something a little more "solid".

 

[Deluks]

Tile backer board is 10mm, double it up if you like.

You could just back fill it with concrete but a thermal bridge is useful. I've seen thresholds 'sweat' where the floor insulation stops

Did the strip that you removed sit under the door frame?

 

[jweaver]

Tile backer board is 10mm, double it up if you like.

You could just back fill it with concrete but a thermal bridge is useful. I've seen thresholds 'sweat' where the floor insulation stops

Did the strip that you removed sit under the door frame?

Yes.. The strip was under the door. When the door was changed, they left it and I assumed it was just some trim, but when I cut it out, I realised it was covering the cavity.. I didn't really have much choice to remove it as it was too thick to tile over... But with hindsight, I might have left it in and then put some kind of trim over the top.. But it would have ment tiling 4-5" short of the door and wouldn't have looked great.

I have some membrane, so after looking again, I think I am going make a 'bag' and then fill it with cement.... I am still not convinced this will be easy as I fear there won't be enough cement to force the 'bag' into the corners (As the membrane is pretty thick)... Its a shame I can't just go with the expanding foam, as that would be easier.

 

[Deluks]

Use thinner polythene. You can ex foam it if you like.