Hi @plimplim,
A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Thank you for your question about repairing a cement sheet where paint has bubbled off.
Can we get a wider shot of where the issue is? This will help our community understand the problem and recommend further advice.
Are you aware of what the white marks are from? Is there concrete above this sheet? Is there a gutter above this sheet?
Cleaning and repairing the peeled paint is reasonably simple but understanding and addressing the reason for the damage is the main thing we need to consider.
To clean the drip marks, use Sugar Soap mixed with water to the ratio that is recommended in the manufacturer's instructions. Use a microfibre cloth in a circular motion to wipe away as much of the stain as possible.
Once cleaned and dry, wear a mask or respirator and use 120 Grit Painted Surface Sandpaper to lightly sand the entire surface paying close attention to any remaining drip marks and the edges where the paint has peeled away.
Now the surface has been sanded, you can paint over the entire surface with colour-matched external paint such as Dulux Weathershield. Most exterior paints, including Dulux Weathershield, are self-priming, so as long as the surface is well-prepared, there is no need for any additional primer.
Keep in mind that if we don't address the dripping issue before this it is likely this will reoccur. Once you've provided some additional details, I'd be happy to offer recommendations on the dripping issue.
Let me know if you have any further questions.
Jacob
