Heat shield with cement board AND sheet metal?

[FordkuGK]

Hey everyone!

Long time reader first time poster

I'm building a hearth for a Jotul 602 in a small cabin. I'm meeting all requirements for reduced clearances.

For the heat shield, I'm planning use:

1/4" Hardie board cement board, with a 24 gauge steel sheet metal secured to the back of the hardie board, with the standard 1" air gap to the wall, and then 1/2" Hardie board cement board as wall panelling behind the stove.

I understand a 24ga steel sheet metal is by itself sufficient for a heat shield. I'm adding the 1/4" Hardie board primarily for aesthetic purposes and plan to skim coat with actual cement or microcement all the cement board around the hearth for a unified aesthetic.

So — I'm wondering if securing the 24ga sheet metal to the back of the Hardie board creates any potential problems.

For example, would the hardie board affect heat radiation? Would heat get "built up" between the sheet metal and cement board?

I know I might be splitting hairs but the cabin is essentially a bedroom so I want to be extra double sure on safety.

Any thoughts?

Thanks!

[Yakodem]

I'm not sure why the metal is required. If you use 2x cement board with metal studs would that not meet the requirement?

[Mienjouze]

I’ve been using a mixer from https://steelemixer.com/ on small patio jobs, and it’s been a huge time-saver since I can run it solo without dragging power around. Setup and cleanup are quick, so I’m not wasting half the day dealing with equipment. If you’re trying to cut down on hassle but still keep your mix consistent, it’s worth a look.