Forming for Suspended Hearth

[Dosache]

First time poster, long time lurker. I am preparing to form for my suspended hearth. I have my cmu block base completed and have decided to use hardie backer board for the bottom of the hearth. What is the opinion on having the backer board rest on the block by an inch or so as opposed to having the backer board placed like plywood would be placed for easy removal? Thanks!

[Gulf]

You can leave the hardi backer in place imo. I don't know about the "or so". But, a half inch is a gracious plenty. Just don't let it cover the holes in the cmus .

[JRPizza]

I used Hardie board and enough overlap to allow me to get concrete into my cores. In the pic I had not cut the angle for the front of my corner, but you can see what kind of overlap I had.

[Dosache]

Thanks for the replies Gulf and Jr Pizza. The suggestion of the overhang (1/2" Gulf) and the photo (Jr) is what I was looking for. I'm ready to do this now.

[JRPizza]

Go for it! I went the backer board route for it's simplicity. No need to support the periphery where the board sits on the bricks. All I did was support the cantilevered front corner, a few 2x4s along the internal seam between boards, and a few in the middle for good luck. No need to remove the board, no seams along the block wall to seal, and it will never rot out .

[Dosache]

These are the exact reasons I went this route JRPizza. I was wondering about the support for the periphery if I went this route so thanks for sharing your build experience. I am also doing a ledge for workspace that will be cantilevered. Thanks again.