In the construction of

masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar; the term ''masonry'' can also refer to the units themselves. The common materials of masonry construction are bricks, building ...

buildings, a fire cutBrannigan, Francis L., and Glenn P. Corbett. ''Brannigan's building construction for the fire service''. 4th ed. Sudbury, MA: National Fire Protection Association :, 2007. Print. or fireman's cut is a diagonal cut along the end of a

joist A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the s ...

or beam where it enters a masonry wall. If the joist burns through somewhere along its length, damage to the wall is prevented as the fire cut allows the joist to fail and leave the masonry wall standing. Without firecut joists, the burnt joists would fail and the ends of the joists would rotate as the joist deflected downwards. The rotation would damage the masonry wall at the connection point and possibly pull the wall inwards.

References

Masonry Carpentry {{carpentry-stub