How to repair surface on limestone retaining wall?

[SN]

i have an old limestone wall that has either been rendered or painted. The surface is now blistering and fall off. Ideas please on how to repair it.

[MitchellMc]

Hi @SN,

The blistering has likely occurred due to moisture in the wall pushing the paint/render off. Has the moisture issue been resolved, and where is this wall? Is it a retaining wall in the garden or a house wall?

You'll need to begin by removing any of the delaminated and compromised paint. If you don't remove it all now, the issue will continue to happen after your repair. I'd suggest blasting most of it off with a power washer and then scraping the rest. If you'd like to restore the smoothness of the wall, there appear to be voids and depressions that need to be filled with Dunlop 5kg Ardit Rapidset Repair Mortar. You'll then be able to render the repaired areas or use a textured paint.

I think the most important issue here is to resolve what has caused the paint to be pushed off the wall and the underlying cement to degrade. This is likely a moisture problem in the cement.

Mitchell

[SN]

Hi Mitchell,

The wall was built about 40 years ago.

It is about 6ft high, surrounds an area of land with a large garden and the  house .

The wall is made from large natural limestone blocks. Should never have been rendered and painted. 

Only blistered in a few places.

Thanks 

[MitchellMc]

I agree, @SN. Rendering it was likely fine, but the paint added a non-porous layer and retained moisture. That's likely led to the limestone degrading. 

I'm pleased to hear it's a garden wall, not a house wall.

Let me know if you run into any difficulties with the repair.

Mitchell