Fireplace hearth extension advice

[infinity_blues]

I am renovating a house built in 1958 and need to bring my hearth to code before I can have new vinyl flooring installed. I tore out the original slate extension and found degraded concrete underneath. About 2-3" thick. Under that is what looks like extremely compacted dirt, but may actually be plaster laid on top of wood slats.

I'm just looking for advice on the best way to go from here. I was thinking of stacking durarock until it is flush with the subfloor, but I'm also wondering if I should pour some concrete down. Pics attached. Will have more later. Any advice appreciated!

 

[bholler]

I am renovating a house built in 1958 and need to bring my hearth to code before I can have new vinyl flooring installed. I tore out the original slate extension and found degraded concrete underneath. About 2-3" thick. Under that is what looks like extremely compacted dirt, but may actually be plaster laid on top of wood slats.

I'm just looking for advice on the best way to go from here. I was thinking of stacking durarock until it is flush with the subfloor, but I'm also wondering if I should pour some concrete down. Pics attached. Will have more later. Any advice appreciated!

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To bring it up to code you need to remove all of that. Then either build a non combustible form or a removable wooden one and pour a new hearth extension slab that is anchored back to the main slab. No combustibles can contact the bottom side of it