Repair double layer firewall?

there may be another wall between your wall and the neighbors wall....this middle wall is the fire wall....your wall should be 5/8 inch drywall ....how much of the wall are u replacing....if just cutting out the wet section towards the bottom of the wall ( maybe a few inches up ) then nothing special to do. no screw pattern needed... cut out bad section and replace that section ....screw or nail....tape and mud....thers nothing special about a fire wall except its thickness