Fireplace levelling

[Lickdan]

Hi there,
Have a heavy slate hearth to lay. Have already floored it and it’s only housing a electric fire on top so no issue. Want to bring the level up about an inch level with floor and just lay hearth floating which I don’t see being an issue. Stuck on what’s best way of going don’t think any damp here as all dry and don’t want to invite damp. Not the greatest with cement. There will be a gap of about 15mm to the floor that is in place including floor board. Question is what’s best easiest way. Was thinking dot and Dab a board in wood or cement or self leveller etc thoughts please.

 

[RandomGrinch]

I'm just a DIY'er so please ignore!
Given the fissures and unevenness of your base, I would use mortar.
I laid my hearth on a mortar bed. Don't worry about being good with cement, a ready mixed mortar: https://www.screwfix.com/p/cementone-general-purpose-mortar-grey-5kg/36857
is really easy to use (just mix in the tub and poor in).
I would fill in the gaps with the mortar first to make a level base. When dry put a damp proof membrane on top, then put some blocks on the base to raise the slate to the correct level, poor in the mortar to your desired level and lay the slate on.
The blocks will support the slate true until the mortar goes off.
I hope that makes sense. Though again, I may be completely wrong!

 

[Lickdan]

Hi mate, that’s pretty much what I’m going to do. May need two of them what you said, it’s 900x350 and about an inch deep. Was gun use some sbr neat paint that on then level with the cement. I have some laminate under lay with damp proof in and lay that then lay the slate floating it’s a heavy piece and won’t go any where thank you

 

[RandomGrinch]

Yeah, get a few. They don't go as far as you may think. And you can always take them back unused!
Your plans sounds good.
Using the blocks to support the slate would be good if you were laying on wet mortar, but if you are letting it float on dry stuff then don't worry.
Good luck!

 

[Lickdan]

Hi sand cemented it tonight used some wood with oil on to partition it how long before I can move the wood please

 

[RandomGrinch]

If you used the Cementone stuff, the tub says sets hard in 12 hours. I would give it a poke first thing in the morning and see how it is.
...cling film wrapped around the wood also works well
Edit:
You could screw some screws into the edge of the wood and just give it a wobble to start breaking it away from the mortar?