Hi there,
Would appreciate some advice please to repair and prevent further cracking in our retaining wall please.
Forgot to also ask about repainting to prevent peeling like this? Should I scrape off and then prime before painting to prevent it? Or something else entirely?
Welcome to the Bunnings Workshop community @gracemc. It's wonderful to have you join us and many thanks for your question about repairing the crack and peeling paint on your retaining wall.
From your photos, the crack appears to run down through the corner of the rendered wall, so I would treat this as more than just a surface crack. Before patching or repainting, it would be worth checking whether the wall is moving, leaning, bulging, or whether the crack has widened over time. If there is any movement, or if the wall is retaining a significant amount of soil, I would recommend having a landscaper, builder or structural engineer inspect it. Filling the crack will improve the appearance, but it will not stop further movement if the wall or footing is shifting.
The planting and soil directly behind the wall also makes drainage worth checking. Water pressure behind retaining walls is a common cause of cracking and paint failure. If water is sitting behind the wall or soaking through the render, paint will continue to peel no matter how well it is prepared. Make sure water is draining away freely and that there are not blocked weep holes or soil sitting too high against the wall.
If the wall is stable and the crack is only cosmetic, clean out any loose render and debris first. For a moving crack like this, I would generally avoid a rigid cement-only repair, as it is likely to crack again. A flexible exterior sealant such as Sika 310ml White Sikaflex Pro+ Polyurethane Sealant would be more forgiving. For deeper gaps, push in a suitable backing rod such as Moroday 6mm x 5m White Gap Filler Rod first, then seal over it.
For the peeling paint, yes, scrape off all loose and flaking paint first. Do not paint over any lifting edges, as they will continue to peel. Once scraped, give the surface a good clean, allow it to dry thoroughly, then sand or brush back any chalky areas. If the render is powdery, bare, or patchy, prime it before repainting with something like Dulux 4L 1Step Prep Primer, Sealer & Undercoat. After that, apply two coats of a suitable exterior masonry/render paint such as Dulux Weathershield Render Refresh.
The key is that the wall must be dry and the cause of the cracking or moisture addressed first. Scraping, priming and painting will give the best finish, but it will not prevent peeling if moisture is still coming through from behind or sitting on the top surface.
You might also find these similar discussions helpful: How to fix retaining wall crack? by @premmas and How to seal cracked retaining wall? by @bob11 .
Please let me know if you have further questions.
Mitchell
