Have polished a "false" chimney breast in lightweight concrete (serpo 138-KC / base with serpo 105). Own build that hides flex pipes from the insert in the fireplace to the chimney breast. It didn’t turn out great, but somewhat... I would like to smooth it out a bit more. Can it be done now with something more amateur-friendly? Sand filler??? It only gets warm from convection heat, so it doesn't reach very high temperatures. But it gets warm.
I have personally "fixed" bad plastering by wetting the wall and filling in with finely mixed plaster. Then, once it has cured, wet it again and brush the entire surface with fine mortar to get the same texture on everything. Just using sand filler will make it pretty smooth; it probably works otherwise with sand filler if the areas aren't too large. I think that mortar and filler expand differently depending on the temperature, so you're likely to get cracks.
Okay, I didn't think you could get the plaster to adhere again. That sounds promising! Smart to brush everything at the end so the texture becomes even. Today, I was advised against sand putty, but recommended to use gips. Any thoughts?
Plaster.... hmm... yes, maybe it's softer and follows the movements a bit... but it also becomes very smooth... Hmm, I wonder if you can mix in a bit of sand... then plaster would probably get completely dissolved if it gets damp... But maybe it's not an exterior wall you should attempt.
If you dampen the wall first, it works to apply with mortar afterward. The dampening prevents the dry wall from drawing out the moisture from the new mortar so it never sets.
If you dampen the wall first, it works to apply with mortar afterward. The dampening prevents the dry wall from drawing out the moisture from the new mortar so it never sets.