Hi @tan_tran81,
Thank you for your question about enclosing an open pergola and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
What you're proposing is certainly possible, but the place to start with a project like this is to consult with your local council to see if it's allowed. They may consider what you're planning to build an extension to your home, which would likely require council approval before construction.
The next thing to consider is the proximity to the fence line. Not only will it make the construction of the walls difficult, but most councils won't allow construction right up to a fence line. This is referred to in construction as "setback". This is something to ask about when you contact your local council for guidance.
If your council is happy for you to proceed, I'd suggest having a look through How To Build a Stud Wall for some guidance on framing.
If your council is not happy for you to proceed, an option is to enclose the pergola with bistro blinds which can offer great weather resistance while still allowing the light in.
Once you've spoken to your local council, I will be happy to assist further.
Let me know if you have any further questions.
Jacob
