<PAGE>   1
                                                                     EXHIBIT 11

                       Elcor Corporation and Subsidiaries
          Computation of Income Per Common and Common Equivalent Share

                    (In thousands, except per share amounts)

1.       Three Months Ended June 30, 1997
         and June 30, 1996

<TABLE>
<CAPTION>
                                                                                      Three Months Ended      
                                                                                    6-30-97           6-30-96 
                                                                                    --------          --------
<S>                                                                                 <C>               <C>     
         Income per Common and Common                                                                         
         Equivalent Share:                                                                                    
                                                                                                              
         Net Income                                                                 $  4,313          $  2,176
                                                                                    ========          ========
                                                                                                              
         Shares:                                                                                              
         Weighted average common shares                                                                       
         outstanding                                                                   8,795             8,767
                                                                                                              
         Adjustments:                                                                                         
         (a)    Assumed issuance of shares purchased under                                                    
                incentive stock option plan using treasury                                                    
                stock method                                                             144               104
                                                                                    --------          --------
                Total Common and Common Equivalent Shares                              8,939             8,871
                                                                                    ========          ========
                                                                                                              
         Income per Common and Common                                                                         
         Equivalent Share                                                           $    .48          $    .25
                                                                                    ========          ========

</TABLE>



2.       Fiscal Year Ended June 30, 1997 and
                June 30, 1996

<TABLE>
<CAPTION>
                                                                                        Fiscal Year Ended     
                                                                                     6-30-97           6-30-96
                                                                                     -------           -------
<S>                                                                                  <C>               <C>    
         Income per Common and Common                                                                         
         Equivalent Share:                                                                                    
                                                                                                              
         Net Income                                                                  $13,002           $10,284
                                                                                     =======           =======
                                                                                                              
         Shares:                                                                                              
         Total Common and Common Equivalent Share                                                             
                                                                                                              
         Three months ended 9/30/96 and 9/30/95                                        8,793             8,843
         Three months ended 12/31/96 and 12/31/95                                      8,843             8,838
         Three months ended 3/31/97 and 3/31/96                                        8,908             8,875
         Three months ended 6/30/97 and 6/30/96                                        8,939             8,871
                                                                                    --------          --------
         Average for Fiscal Year Ended 6/30/97 and 6/30/96                             8,871             8,857
                                                                                    ========          ========
         Income Per Common and Common                                                                         
         Equivalent Share                                                           $   1.47          $   1.16
                                                                                    ========          ========
</TABLE>