Hi @cm24,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
I have a couple of questions that should help direct our plan of attack.
Does that window open and can we get some photos of it from the outside?
Is that wall brick or besser block?
The skirting boards are made of MDF, which is like a highly compressed cardboard. Like cardboard, it cannot handle moisture well and will pick up any water that comes in contact with it. You can see that the skirting board running along the wall is swollen to a point about halfway along, which makes me suspect that you have a water entry issue around the frame of the window. The water is entering through the end of the MDF and travelling along it up to that point.
My suggestion is to fully remove the small return skirting board and the full length of the one running along the wall. I'd suggest using a wood chisel or a pry bar to remove these pieces of skirting.
Once they are off, inspect the frame around the window for an entry point. If you get some photos from both inside and outside once the skirting has been removed, I'd be happy to give it a look.
It's likely there will be an entry point somewhere that you can fill with a suitable gap filler to prevent water entry. Once we have located this entry point, I'd be happy to advise on the best product for this location.
Once the water entry issue is dealt with, you can reattach a new skirting board of a similar size. If this is a block wallas I suspect, you can do this with Liquid Nails.
Let me know how you go and don't hesitate to ask any further questions, I'm happy to clarify and offer further advice.
Jacob
