![firebrick in different colors](https://www.portlandstoneware.com/wp-content/uploads/2016/02/firebrick.jpg)
Type N is used for interior walls and exterior walls above grade and Type S is recommended for exterior walls at, or below, grade. Dragon Dark is a Type N mortar and is used where a charcoal gray color is preferred.
Type N is used for interior walls and exterior walls above grade and Type S is recommended for exterior walls at, or below, grade. Dragon Dark is a Type N mortar and is used where a charcoal gray color is preferred.