I'm extending my brick Hearth 16" to meet my stove's front clearance requirements. There is a 1/8" gap (cardboard is inserted in gap in photo) between the floor joist and original concrete hearth extension which will get filled when I pour cement to fill the 2" gap between the subfloor and old brick hearth.
Is the 1/8" gap necessary for thermal expansion to isolate the masonry from the floor joist?
![[Hearth.com] Is the gap between the floor joist and hearth a structural requirement? [Hearth.com] Is the gap between the floor joist and hearth a structural requirement?](https://www.hearth.com/talk/data/attachments/133/133164-09c0637a42f3f1d36bd3dc163d60baee.jpg?hash=24A67C4vMQ)
Is the 1/8" gap necessary for thermal expansion to isolate the masonry from the floor joist?
![[Hearth.com] Is the gap between the floor joist and hearth a structural requirement? [Hearth.com] Is the gap between the floor joist and hearth a structural requirement?](https://www.hearth.com/talk/data/attachments/133/133164-09c0637a42f3f1d36bd3dc163d60baee.jpg?hash=24A67C4vMQ)