How to fix gaps at ceiling and around window?

Rik

I have just moved into this tiny home and the last owner half did the gib-board and stopping but there are some big gaps and rough edges all over the place.  Looking for advice for a complete beginner as to how I should fill these gaps?

Gap in the corner is about 15mm (photo 1)
Gap at the ceiling at its largest point is 30mm (photo 2)

Gap above the window is about 10mm. (photo 2)

All help greatly appreciated! Many thanks!

Photo 1

Photo 2

EricL

Hello @Rik 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your gib board.

It appears that the gaps are too big, and I suggest cutting and replacing part of the gib so that you have tighter tolerances. 

Here is a link to the plasterboard installation manual: Gyprock Install Manual 

Here are some handy step-by-step guides:

• How To Plasterboard A Stud Wall
   
• How To Attach And Plaster An External Corner
   
• How to plasterboard a ceiling

If you have any other questions we can help with, please let us know.

Eric