What should be done before installing flashing around a window opening?

Before installing flashing around a window opening, it is essential to ensure that the opening is clean. Having a clean surface allows the flashing to adhere properly and creates a better seal against water intrusion. Debris, dust, or old caulk can interfere with the effectiveness of the flashing, leading to potential leaks and moisture problems in the future.

This cleaning process also allows for a proper examination of the window opening for any issues like rot or damage that should be addressed prior to installation. Ensuring the surface is clean helps promote effective installation practices and contributes to the overall integrity of the window assembly.

The other options, while they may be relevant in different contexts, are not directly related to the immediate preparatory steps necessary for installing flashing. For instance, removing the sash could be helpful for certain repairs or upgrades but is not necessary just for installing the flashing. Similarly, marking the placement of insulation pertains more to thermal performance rather than the direct installation process of the flashing itself. Ensuring a bracket support for the window may be a part of the overall window installation, yet it does not prelude the crucial step of cleaning the opening before flashing installation.