Hole in Floor

[diynoob]

I have the floor up ready for the tiler on Monday. There's quite a deep hole near the patio doors though which I guess I should fill now so it's set in time for tiling.

Shall I just fill with concrete up to the floor level? Do I need to worry about damp proofing or anything like that? There's various bits of plastic poking out.

 

[Chud]

Caveat - I'm not a builder so seek advice from someone more knowledgeable...but...I wouldn't just fill with concrete - that looks to me like the hole or trench is the cavity for your wall - if you just fill it with concrete you're going to create a bridge for both water ingress and thermal.

You probably need to apply a liquid dpc to the inside face of the exterior wall or even attach a piece of plastic DPC to the inside face with a bit of gripfill etc before you put in any type of fill. secondly for the fill I would probably look at a cavity wall insulation or something like perlite that you can screed over the top of.

 

[Tigercubrider]

is that where a dwarf wall was? and french doors? Replaced by the patio doors?

I had something similar and excavated down to a stable concrete, added blinding sand, dpc membrane, and painted liquid DPc to join everything before adding concrete to level it up. Then parquet inserted in the fresh gap.

the Previous owner had an aluminium patio door to replace a pair of french windows and dwarf wall on either side.
The fitters had just roughly finished the floor where the wall had been, and the original parquet where the doors had been was a bit rotten, either through a bad set of original french doors, or because of a badly fitted aluminium patio door.

 

[diynoob]

It looks like it was previously just an exterior wall that was knocked through. So the trench is actually the cavity as Chud says.

I'll do a bit more googling but it seems that if I apply the dpc incorrectly I could end up making it worse.

 

[diynoob]

I hoovered out the 'trench' to get a better look. I guess the blue poking out of the floor is a DPM and the black line on the external wall is a DPC. Should I paint liquid DPM from the blue DPM, through the trench and up to the external wall to the DPC?

 

[JohnD]

.

 

[diynoob]

Found some other threads on this topic. It's a lot easier to find them now I know that the trench is a wall cavity!

https://www.diynot.com/diy/threads/door-threshold-and-cavity-wall.239249/
https://www.diynot.com/diy/threads/patio-door-threshold.482789/

The advice is the same as Chuds, ie line the trench with DPM, add insulation to prevent thermal bridging and then cover with screed.