Old Fireplace Floor Filling Question

[Justin Bodley]

Hi!
Currently renovating the living room in our 'new (old)!' house. I pulled up 2 slabs in front of the fireplace earlier, expecting to find floorboards underneath. However I found this. I need to fill and level it as I will be installing LVT flooring over the top. The chimney will be blocked off as I'm currently building a media wall that will have a recessed electric fire. What would you use to fill the gap and level? Don't really want to use expandable foam! Would you use some sort of screed? I've knocked the concrete down just below the level of the floorboards. Any advice would be great!

 

[Wayners]

Sbr then a bag of suitable ready mixed floor leveler is easy enough to fill depth.
I've also mixed my own mortar mix and filled if I had some.
You can also buy ready mixed mortar.

Just be aware there won't be a dpm under that floor like plastic . Never is where there is a real fire.
Make sure fireplace is vented so you don't get damp problems

 

[dazlight]

No Dpm under that. So best way is plywood your floorboards.
Then fill fire place with ardex na screed and a liquid Dpm