Best product to fill small gaps between plasterboard and wall

[wanderlust]

Hi lovely people

I've sealed off some leaks on my flat roof extension over my bathroom and now I am repairing some water damage at the junction of the plasterboard roof and the wall. The edge portion needs to be filled. I tried Polyfilla previously but I don't think it's the best water resistant product? I've run my dehumidifier overnight to help dry out any residual moisture .

Any better products that I can fill then paint over tomorrow?

Kind wishes
Michael

 

[Silentrunning]

You say “plasterboard roof” but are you referring to the ceiling? If your ceiling got wet, I would recommend replacing all the plasterboard.