How to repair cement sheet surface?

[plimplim]

 hi

 the back wall of our place has some water damaged cement sheet. Can I clean and fill this? Especially the bit where the cement sheet internal is exposed.  
thanks!

paul

[JacobZ]

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

[plimplim]

Thanks Jacob that’s super helpful.  The bigger problem was that the flashing above this part of the wall had fallen off (for years) so water running off the balcony was collecting that extra debris. The flashing has been refitted, now the plan is to add a gutter under that flashing to fix the problem of water run off from the balcony.

on the panel that needs to be fixed there is a bit where the top layer has peeled away, should I fill this before repainting?

 

[JacobZ]

Hi @plimplim,

It's good to hear the cause of the issue has already been rectified so you can move on to the aesthetic repair of the cement sheeting.

After sanding back the area where the paint has blistered away, it's worth applying a coat of Dulux 1Step Prep Primer, Sealer & Undercoat to help smooth and flatten the surface before painting over everything with your colour-matched exterior paint such as Dulux Weathershield.

There's no need to prime everything, but the additional primer where it has blistered away will essentially act as a filler to keep everything flat.

Let me know if you have any further questions.

Jacob