Materials for fire blocking
Materials approved for fire blocking are just common building materials.
2-by (1-1/2 in. thick) lumber. Two layers of 1-by lumber. One layer of 3/4-in. plywood with 3/4-in. plywood covering any seams.
One layer of 3/4-in. particleboard with 3/4-in. particleboard covering any seams. 1/2-in. drywall.
1/4-in. cement board.
Batts or blankets of mineral wool or fiberglass insulation secured in place.
Cellulose insulation installed as tested for the specific application.
Approved spray foams and caulks.