How to fix Limestone retaining wall pitting and degradation?

Mick_6000

Hello,

I am seeking some assistance with preserving my limestone retaining wall I had installed around 13 years ago in Perth.

I have noticed some of the blocks have started pitting and degrading, gradually getting worse over time (image below).

Would the correct course of action be to clean the blocks, then apply a sealer such as the Crommelin Limestone And Sandstone Sealer? 

https://www.bunnings.com.au/crommelin-15l-limestone-and-sandstone-sealer_p0961785

• If so - what cleaner would be recommended?
• Would I need to infill the pits with a similar colour concrete mix to prevent further pitting before sealing?
• And I have read in the reviews that the sealer can be corrosive to paint, so would the deck and colourbond fence need to be drop sheeted?

MitchellMc

Welcome to the Bunnings Workshop community @Mick_6000. It's wonderful to have you join us, and many thanks for your question about restoring a limestone wall.

You’re certainly on the right track with how you’re thinking about this.

The pitting and surface degradation you’re seeing is quite common with limestone over time, particularly in exposed areas. Cleaning and then sealing the blocks is the correct overall approach to slow further deterioration. A product like the Crommelin Limestone and Sandstone Sealer is well-suited to this type of application once the surface has been properly prepared.

The part that can be challenging is repairing the existing pits. Standard mortar mixes are generally grey, which will stand out quite noticeably against limestone. To get a closer colour match, you would ideally be using a white cement based mix. White cement can be harder to source, so it’s worth speaking with your local Bunnings Special Orders team to see if they can obtain it for you. If true white cement isn’t available, an off-white or cream cement can sometimes be used, and you can add a small amount of white oxide to lighten it further and bring it closer to the limestone colour. Even then, expect the repairs to be visible up close, but they can be made far less obvious.

Before any patching or sealing, clean the wall thoroughly. A gentle clean with water and a stiff nylon brush is usually sufficient. Avoid acidic cleaners, as they can accelerate limestone damage. Allow the wall to dry completely before attempting any repairs or sealing.

Once repairs are done and fully cured, sealing the wall is a good preventative step. Sealing will help reduce water ingress, which is a major contributor to ongoing pitting and breakdown. As noted in the product reviews, the sealer can affect painted surfaces, so you should definitely protect nearby areas. Drop sheet the deck and fence thoroughly, using plastic sheets taped securely along the edges. It is much better to overprotect these areas than risk splashes or overspray.

Please let me know if you have any questions.

Mitchell