What is the name of the joint located between the top of a wall and the underside of the floor above?

The joint located between the top of a wall and the underside of the floor above is known as the head-of-wall joint. This specific joint is crucial in firestop systems because it allows for movement and insulation at the intersection of walls and floors while helping to maintain the fire-resistance rating of a building. It typically accommodates vertical movement caused by factors such as settling or temperature changes. Properly managing the head-of-wall joint with appropriate firestop materials is essential to prevent fire and smoke from spreading through these critical areas.