Hi @ukn353,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Was this something flagged in a building inspection report?
If so, did they provide any written details about what the issue actually is?
The main function of these skirting rubbers is to keep dust from getting into the cavity behind the brick. It helps with weather sealing, but this is not its primary function.
Something to note about rubber, is that it expands and contracts depending on the temperature, with it being at its most expanded when it is cold. I would make sure to inspect the rubber when it is cold as these gaps may close up when the rubber is expanded, meaning you wouldn't really need to do anything.
If the gaps are still there when the rubber is at its most expanded, you could always seal them up with a bit of Black SikaSeal if you'd like to, but this is only going to prevent dust from getting into the cavity.
If there are issues relating to water, this is not going to fix them.
Let me know if you have any further questions.
Jacob
