How thick should gypsum board be to separate the garage from the residence and its attic space?

The appropriate thickness of gypsum board to separate the garage from the residence and its attic space is typically 5/8 inch. This thickness is specifically chosen for its fire-resistance properties, which are crucial in creating a barrier between a garage and living spaces. The International Building Code requirements generally specify that a minimum of 5/8 inch Type X gypsum board is necessary to provide adequate fire protection and a sufficient separation to minimize risk of fire spread.

Using 1/2 inch gypsum board would not meet the fire-resistance provisions mandated for such separations, making it less effective in fire containment. Thicker options, such as 1 inch, may exceed what is required and can also lead to unnecessary additional weight and cost without providing significant added benefits in the context of fire resistance. Therefore, 5/8 inch gypsum board is considered the standard for this application, striking a balance between safety, structural requirements, and practicality.