What do I need to use to ensure the skylights do not leak when installing?

No sealants or adhesives of any type are needed with VELUX deck and curb mounted skylights.  These VELUX skylights are provided with a 10 Year No Leak Warranty as long as they are installed in accordance with the included installation instructions and are flashed with the appropriate VELUX flashing kit.  Together these VELUX skylights and flashing kits form three (3) layers of water protection; 1) VELUX skylights are constructed to seal tight to the roof deck or curb, 2) adhesive underlayment provides secondary water protection, and 3) flashings provide primary water protection without relying on sealants that can break down over time.  Since additional installer sealants and adhesives are not part of the installation instructions for deck and curb mount skylights, applying sealants or adhesives to these VELUX skylights will void the product and installation warranty.

Gorilla Glue is a registered trademark of The Gorilla Glue Company and Flex Seal is a registered trademark of Swift Response, LLC.