The maximum mortar joint allowed between the firebricks in this fireplace is 1/4". The joint to the left of the tape is about 1"; the joint to the right, about 3/4".
Excessive Mortar JointGallery: GalleryDescription: The maximum mortar joint allowed between the firebricks in this fireplace is 1/4". The joint to the left of the tape is about 1"; the joint to the right, about 3/4".