Exhibit 21

BUILDING MATERIALS CORPORATION OF AMERICA    LIST OF SUBSIDIARIES

|COMPANY                                       |                                          | STATE OF INCORPORATION             
|--------------------------------------------- | ---------------------------------------- | -----------------------------------
|BMCA Acquisition Inc.                         |                                          | Delaware                           
|                                              | Elkcorp                                  |                                    
|                                              |                                          | Elk Premium Building Products, Inc.
|                                              |                                          |                                    
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|                                              |                                          |                                    
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|                                              |                                          |                                    
|                                              |                                          |                                    
|                                              |                                          | Elk Technology Group, Inc.         
|                                              |                                          |                                    
|                                              |                                          |                                    
|                                              |                                          |                                    
|                                              |                                          |                                    
|                                              |                                          | Elk Group, Inc.                    
|                                              |                                          | NELPA, Inc.                        
|                                              |                                          |                                    
|BMCA Gainesville LLC                          |                                          | Delaware                           
|BMCA Quakertown Inc.                          |                                          | Delaware                           
|BMCA Insulation Products Inc.                 |                                          | Delaware                           
|Building Materials Investment Corporation     |                                          | Delaware                           
|Building Materials Manufacturing Corporation  |                                          | Delaware                           
|                                              | HBP Acquisition LLC                      |                                    
|                                              | BMCA Fresno LLC                          |                                    
|                                              | BMCA Fresno II LLC                       |                                    
|GAF Leatherback Corp.                         |                                          | Delaware                           
|GAF Materials Corporation (Canada)            |                                          | Delaware                           
|GAF Premium Products Inc.                     |                                          | Delaware                           
|                                              | Wind Gap Real Property Acquisition Corp. |                                    
|GAF Real Properties, Inc.                     |                                          | Delaware                           
|GAFTECH Corporation                           |                                          | Delaware                           
|LL Building Products Inc.                     |                                          | Delaware                           
|                                              | Ductwork Manufacturing Corporation       |                                    
|Pequannock Valley Claim Service Company, Inc. |                                          | Delaware                           
|South Ponca Realty Corp.                      |                                          | Delaware                           

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