Hearth compliance

[Darren12]

I have a wood burner that sits on a wood board floor with a tile hearth built around it. I have been advised that this is non compliant.

The hearth is an odd shape/size as the burner sits askew in the corner. It's been suggested to me that I cut a piece of fibre cement to existing hearth template and place under the whole lot.
What board should I use and what thickness should it be?
Is it easy to cut cement board?
Also, if I butt 2 pieces together do I need to seal the join?
Cheers

[Jason]

Hi @Darren12,

Many thanks for joining the community here at Workshop. We're really pleased to have you join us and look forward to reading about all of your projects and plans for around the house and garden.

Let me tag a couple of experienced members in @Brad and @ProjectPete to see if they might like to kick off this discussion for you and share how they might tackle the project. 

Welcome,

Jason

[Brad]

While I think the fire box has some distance to the floor and not looking up compliance codes for now, I do see a problem with the tiles that may be from putting them directly on floorboards which can move with the changes in humidity.

Disclaimer: My Grandfather was a tiler who also taught my Father and Uncle how to be tilers ( neither stayed in that trade ) I know some of the basic concepts but I would avoid things like modern showers unless I did a lot of research first. Given what I do know I would use a product like the ceramic tile underlay to avoid the movement of the boards cracking the grout in the tiles and it would be best put in as one piece, I can see why you may want to use two pieces and if going down that path don't join where there is also a join in the tiles and I would put some filler in the join if I had to do a two piece install. My inner welder says nail the sheet to the floor but I can see that having it floating may stop the cracks, may be a good time to read the instructions before deciding.

Hope that helps some.