Extend Pre-fab Surround

[kahluwal]

Hi everyone, I've tried to read as much as I can before asking but I just can't find the clear answer. I would like to extend my fireplace surround a few inches from the wall, based on the manual it says I can do 4" from wall at the closest part near the fireplace with combustible material. What I am imagining is building a 4"x12" frame and nail that to the existing studs, concrete board over that, and tile over that. My concern is if this design conflicts with the hearth requirements which state 16" out and 8" on the sides, it is on concrete and we are just going to lay tile on the ground so no raised hearth.

I hope I am clear, if not I added some pictures from the manual, the manual itself, and a picture with some drawings on it for dimensions (I know very crude). I can answer any questions to clarify more too. If anyone has any advice, I am all ears. Thank you!

Update 1: Found a picture to explain what I am looking to build, as you see the surround columns come right up to the fireplace, but I am sure they used wood framing on the inside. Is this safe to do given the 8" to the sides rule for the hearth?

 

[DAKSY]

Don't use combustible materials & you'll be good to go.
Use steel studs as your framing & attach concrete board
to the studs with the appropriate screws.

 

[kahluwal]

Don't use combustible materials & you'll be good to go.
Use steel studs as your framing & attach concrete board
to the studs with the appropriate screws.

I'll look more into it, I saw a bunch of comments talking about them being flimsy previously so I thought it wasn't preferred.

 

[begreen]

I'll look more into it, I saw a bunch of comments talking about them being flimsy previously so I thought it wasn't preferred.

Steel studs come in different gauges and strengths. The lightest ones are pretty flimsy, though for this small area that might matter much. It's not load bearing.