alter table datatype giving error date to bit

IF EXISTS (SELECT * FROM SYS.COLUMNS WHERE NAME =N'Case_Escalated__c' AND OBJECT_ID = OBJECT_ID(N'[Case]')) begin alter table [Case] alter column Case_Escalated__c bit nullprint 'Case_Escalated__c altered sucessfully for [Case]' endMsg 1792, Level 16, State 1, Line 3Alter table 'Case' failed because the added fixed column might cause existing data to go beyond the maximum allowable table row size of 8060 bytes.