There you have it. That's what happens.
If you take a closer look at the photo though, you can see clearly what the issue is with Portland cement. It holds onto water like a sponge; an unbreathable sponge at that. Notice how the concrete render is cracking in a grid. Those cracks are occurring at the joins between bricks which are filled with concrete mortar. The mortar has retained the moisture, which has then seeped into the concrete render, and ultimately destroyed it.
This knowledge is crucial if you're thinking of repairing an old stone wall, rendering a traditional building, or maintaining a natural home. As Period Living says, "Sadly, the wrong techniques and materials are all too frequently used for repairs so moisture is sealed in, resulting in damage and decay, often with disastrous consequences to walls and floors."
So what should you use instead? Lime plaster and cretes, clay plasters and mud mortars are the way to go. Here's a useful article on the subject.
Have you restored an old natural home? Do share your tales and your tips.
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3/10/2018 02:26:45 am
I appreciate your article talking about using concrete as a render. I see everything that you're pointing out in that picture. The thing that stands out to me is how its cracking everywhere. I need to get my home re-rendered, so I think I am going to seek out a rendering service to help me.
3/10/2018 12:01:23 pm
Yes, the myth that concrete is 'strong' is slowly disintegrating. It cracks because it's rigid. Lime and clay based mortars and renders are not just breathable, but much more flexible too.
4/10/2021 12:39:19 pm
Before you start you need to guarantee that the surface you are delivering is liberated from soil, dust, oil, oil, paint, silicone or friable material. Smooth thick surfaces with low retention rates like concrete or metal window casings ought to be ready with a "run coat" preceding utilization of the render. A scramble coat is basically an extremely amazing blend of concrete and water which is flicked over the divider or metal window outlines making a surface for the render to hold to. Permit the scramble coat to dry for something like 24 hours before you begin to apply the render.
25/10/2022 05:22:46 am
When you use concrete as a render, you are essentially creating a protective barrier around your home. This barrier will protect your home from the elements, as well as provide an extra layer of insulation. Concrete is an extremely durable material, so you can rest assured that your home will be well-protected for many years to come.
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