The lintel is steel with polysteryne insert for insulation. There is a long one at the front for the garage door and a short one at the back for the single exit door.
Brick construction for the walls.
Ceiling of garage has been covered by thick plasterboard and building inspector is happy with that. But my builders just stuck plastic fascia board to the underside of the lintels and inspector has said it must come off and be replaced.
But builders have gone bust and I can't get anyone out to such a small job.
Your lintel wants coating with a fire resitant paint such as bitumen paint or it's like.
I assume there is a concrete lintel in front(external to garage) of RSJ or brick/block work.
You then need to build a frame around RSJ so you can fix plasterboard, the pink boards you will need one single board covering, with the standard boards you need to double board, but controls like to see the pink stuff.