Lime plaster takes considerably longer to cure than gypsum plaster, weeks rather than days for each coat to properly set, and can take a year or more to fully carbonate and reach its final hardness throughout its full depth. This is normal, expected, and one of the main reasons lime work needs to be planned into a project timeline properly rather than treated like a faster modern alternative.
Gypsum plaster sets through a chemical reaction that's largely complete within hours, which is why it can typically be decorated within days. Lime plaster cures through carbonation, a much slower process where the lime absorbs carbon dioxide from the air and gradually converts back into calcium carbonate, working from the surface inward over an extended period. It's a fundamentally different, slower chemistry, not simply a slower version of the same process.
In the first few days, a lime coat needs to be protected from drying out too quickly, direct sun, strong wind, or a heated room can all cause the surface to dry before it's properly cured, leading to cracking or a weak, powdery finish. Over the following weeks, the coat continues hardening and can typically take light handling and preparation for the next coat, if multiple coats are being applied. Full carbonation through the entire depth of the plaster, not just the surface, can take many months to over a year depending on thickness, ventilation, and conditions.
The most frequent lime plastering failures we see come from a contractor unfamiliar with the material treating it like gypsum, applying the next coat too soon, decorating too early with a paint that seals the surface before curing is complete, or exposing a fresh coat to conditions (direct heat, fast drying wind) that cause it to fail before it's had a chance to properly set.
If lime plastering is part of a wider refurbishment, it needs to be sequenced with this timeline in mind, generally as one of the earlier trades, with enough time built in before final decoration. On a multi room project, we typically stagger rooms rather than plastering everything simultaneously, so each area gets the curing time it needs without holding up the whole project unnecessarily.
Lime plaster cures best in a moderate, stable environment, not too hot, not too cold, with reasonable humidity and airflow but not direct drafts or blasting heat. In winter, some protection or moderate heating may be needed to prevent frost damage before the plaster has hardened enough to withstand it. In summer, protecting fresh plaster from direct sun and rapid drying matters more.
Not safely, in any meaningful way. Lime's carbonation process is chemical, not simply a matter of moisture evaporating, so heating a room aggressively or using fans to dry the surface faster doesn't speed up genuine curing, it just risks drying the surface prematurely while the plaster underneath is still soft, which is one of the more common causes of cracking and poor bond. The honest answer is that lime plastering needs to be planned around its own timeline, not compressed to fit a shorter one.
This depends on what you're painting with. Breathable finishes like limewash can generally be applied once the plaster has had adequate initial curing time, often a few weeks, though full carbonation continues well beyond that point. Standard modern paint should be avoided on lime plaster regardless of timing, since it seals the surface and works against the material's breathability, covered in more detail in our guide on what paint to use on lime plaster.
