How Long Does Plaster Take to Dry?
It can be a long wait, but worth it in the end
Highlights
Plaster needs time to dry to the touch, then fully cure, after application.
Humidity, temperature, and ventilation all affect plaster drying and curing times.
You need to let plaster cure completely before moving on to the next phase in your project, such as painting or wallpapering.
Forget plastic, it's plaster that's fantastic. Often considered a precursor to drywall, plaster still has its place in modern homes, as it's beautiful and eco-friendly. If you decide to use it, you need to know how long the plaster takes to dry, as its drying time affects what you can do next and when you can do it.
Plaster Drying vs. Curing
It’s important to understand the difference between plaster drying and plaster curing. When plaster dries, moisture evaporates from the surface of the material. The plaster becomes dry to the touch and appears set.
Curing is a longer, more involved process. All the moisture evaporates when plaster cures, leaving a hard, completely dry material. "Dry" plaster may still contain some moisture beneath the surface. It will look and feel dry, but if you sand the plaster, you may discover it's still wet.
Painting or otherwise treating a plaster wall before it's fully cured can affect your final results. As moisture seeps out of the plaster, it will affect the finish, causing your paint to chip or your wallpaper to peel away.
Finishing the wall before the plaster is cured also affects the integrity of your project. The paint or wallpaper can trap the moisture inside the wall, making the plaster more likely to crumble and deteriorate. Before you move on to the next step in your project, such as painting your walls, give your plaster ample time to dry and cure.
Time It Takes Plaster to Dry
How long it takes plaster to dry depends on the type and amount of plaster you use, and your local weather conditions.
Plaster typically needs 1 to 4 hours to dry to the touch. Each layer needs a few hours to dry if you're applying an undercoat or finishing plaster. A special plaster, such as lime plaster, may need up to one week to dry to the touch.
Time It Takes Plaster to Cure
Plaster needs much longer to cure fully than it does to dry to the touch. When plaster is fully cured, all the moisture is gone from the material, leaving it rock solid.
Depending on the type and amount, plaster typically needs anywhere from a few days to a couple of weeks to cure completely. If you're patching a plaster wall, the patched area may cure in a couple of days. If you're coating the entire wall in plaster or building a plaster wall from scratch, you may need to wait two weeks or longer for it to cure.
What Affects Drying and Curing Times
Several factors affect how long plaster takes to dry and cure, including:
Humidity levels: Water must evaporate out of the plaster to dry. When humidity levels are high, it takes longer for water to evaporate, leading to longer drying and curing times.
The amount of plaster: If you apply the plaster in thick coats, it will need more time to dry, as there's more moisture and the water has more layers to travel through.
Temperature: Ambient temperature also affects drying times. Colder temperatures slow down drying, and hotter temperatures speed it up. The ideal temperature for plaster drying is a comfortable room temperature. When a room is too hot, the plaster can dry too quickly, causing cracks.
Airflow: Good ventilation can reduce plaster drying times, as decent airflow helps moisture travel out from the material more efficiently. Opening a window may be all you need to do to improve ventilation and reduce drying time.
Why It’s Important to Wait for Plaster to Dry
Painting a plastered wall before the plaster is fully dried and cured can affect the quality of the paint job or the plaster itself, depending on the stage of the drying process. If you paint before the plaster is dry to the touch, the paint won't adhere well to the material and will flake or peel off. You may also notice adhesion problems when you apply the paint or as it dries.
Painting too soon can affect the quality of plaster. If the plaster is dry to the touch but not fully cured, the paint can create a barrier, preventing the remaining moisture from escaping. The trapped moisture can weaken the plaster, causing it to crumble.
Signs Plaster Is Dry
As plaster dries and cures, its appearance changes:
When you apply wet plaster, it's brown.
As it dries, the plaster turns light pink.
It's fully cured once the entire surface is light pink, with no brown spots or wet-looking areas.
Frequently Asked Questions
Yes, to some extent, you can speed up the time it takes plaster to dry and cure. Choose a time of year when humidity levels are somewhere in the middle, neither too high nor too low, to allow moisture to evaporate from the plaster effectively. Also, open a window or set up a fan in the room to improve ventilation.
Don't use a dehumidifier in an attempt to speed up drying time, as a dehumidifier may suck moisture from the air too quickly, leading to crumbly plaster.
Heat can help plaster dry faster, but it's very easy to get too much of a good thing. When exposed to high heat during the curing process, plaster can dry out too quickly, leading to cracks and affecting the material's integrity. The recommended drying temperature should be listed on the plaster's packaging. If possible, set the thermostat in the room to that temperature, but not any higher.
Plaster can be a difficult DIY to master, especially if you plan to plaster an entire room, rather than patch a small area. Before you begin a plaster DIY project, you need to know which tools and type of plaster to use. It's also important to know how to prepare the surface and apply the plaster for a smooth finish. If that all sounds like a lot of work, you may prefer hiring a local plaster repair contractor to do the job.