Dehumidifiers

Can You Use a Dehumidifier to Dry Plaster

A dehumidifier is a must-have appliance if you live in an area that experiences high humidity in the air. It has lots of benefits in helping control air moisture and preventing possible water damage in a home. And because of its air drying benefits, people get curious about whether you can use a dehumidifier to dry plaster.

You cannot use a dehumidifier to fasten plaster drying, but you could use it to reduce the moisture level to the recommended level. Plaster has its drying time under standard conditions. Even though you can accelerate the drying during wet weather, you can still cause the plaster application to crack during rapid moisture withdrawal.

A dehumidifier can make plaster dry right when used appropriately, but you cannot use the same appliance to quicken plaster drying. You can only use it to set the standard plaster drying conditions. Continue reading to find out why you cannot use a dehumidifier to fasten plaster drying.

Why You Should Not Use a Dehumidifier to Dry Plaster

According to masonry experts, controlled and uncontrolled environmental factors at a job site can reduce the plaster drying and performance, regardless of the workmanship or material quality.

That’s why it’s always best to investigate the job conditions before starting a plastering project. What if you applied the plaster and it’s taking too long to dry. Can you use a dehumidifier to fasten the plaster drying?

No! When you fasten the process by withdrawing the moisture in the air, you might overdo it, causing the plaster to lose the water too fast, leading to cracks.

What’s more, veneer applications like the conventional plaster finish coats are thin, around 1/16-inches and 3/32 inches, compared to the traditional basecoat finish, around 1/2-inches and 7/8 inches. Such applications are associated with excessive moisture withdrawal.

Conventional basecoat plaster applications require a significant air movement to remove the water once the plaster has settled. In contrast, veneer and traditional plaster finishes require a minimal amount of circulation.

If you’ve worked at a plaster site, the plastered walls and floors require watering until it dries up. An ideal moisture level is required (between 60% and 80%) to keep the plaster intact and allow gradual drying.

Humidity and Temperature

The moisture absorption and removal rate of a plaster system during application also affect the finish type’s performance, primarily noticeable in veneer plaster applications.

An example is when working with a gypsum base in veneer plaster applications. When veneer plaster is added to the gypsum base under normal conditions, the surface paper will absorb the moisture from the plaster.

That causes the board face to expand slightly. The result is a slight outward pressure that makes it curve outwards. And during the plaster application, the wet plaster base side expands, thus bending the panel.

When the plaster settles, it does also expand a little, leading to the pressure pushing together the adjacent base panels at their joints.

When you allow the plaster to dry normally, the pressure goes away, and there is a slight shrinkage during the drying. The best part is, the pressure is enough to allow the joints to stay together.

When you run a dehumidifier for rapid drying, there is an excessive shrinkage, eliminating the needed pressure to keep the adjacent edges together, leading to open cracks.

If you want to achieve satisfactory plastering results, the humidity and temperature conditions of the room should remain standard. The relative humidity should be higher than 50% and the temperature above 55°F.

Low humidity – High Temperature

When you reduce the relative humidity using a dehumidifier, but the temperature remains high, the plaster will experience rapid drying, leading to even cracking.

The issue gets even worse when you use a dehumidifier that has a fan – rapid drying increases when air gets circulated and displaces at a high rate.

Under such conditions, your plaster application gets exposed to the risk of excessive shrinkage and dry out.

What is Plaster Dryout?

It’s the result of removing water from plaster application so fast that it doesn’t get the chance to hydrate fully. When the dry out occurs, it results in a soft, powdery surface in walls and ceiling. The shrinkage causes visible cracking, thus compromising the quality of the plaster.

How to Prevent Dryout

You can prevent dry out and shrinkage cracking by dictating the Jobsite conditions. Here are the Jobsite remedies you can improve to help the dry plaster right:

Keep the Humidity Levels High for Veneer and Regular Plaster: avoid running a dehumidifier to dry the plaster faster. Instead, make sure there is enough humidity in the room by monitoring it using a hygrometer. If typical, that’s okay. If the relative humidity is below average, you can wet the floor or minimize the room ventilation. That way, you can maintain the humidity level as the water evaporate.

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Reduce Humidity for Conventional Plasters: these plaster applications require better ventilation than do veneer plasters. That is because you use more water and a thicker basecoat plaster application. You could keep the windows open to provide sufficient air circulation required for drying. If the room has no windows, use a dehumidifier set at 60%-70% humidity to remove the moisture mechanically.

When to Use Dehumidifier to Help Plaster to Dry

If the job site is in an area that experiences extremely high humidity, to an extent it’s over 100%, you can use a dehumidifier to lower it to 60% – 80%. That’s the ideal humidity level needed for proper plaster drying.

The plaster must hydrate properly during its setting process. Removing the moisture too soon and too much could compromise your plastering application quality.

Related Questions

How long does plaster take to dry?

It depends on the type of plaster, application size, and humidity in the room. Some plasters take days, other weeks, while some take even a month to completely dry. When the humidity levels are high, the plaster application will take a long period to dry. However, since it stays hydrated, it dries slow but efficiently – no cracks or dry out.

Can I use a heater to dry plaster?

The answer is still no. The plaster needs to stay hydrated during its drying process. When you heat the room, you increase evaporation, thus fastening the drying. That results in dry-out and shrinkage cracks that reduce your plaster finish quality.

Refrain From Using a Dehumidifier to Dry Plaster

Can you use a dehumidifier to dry plaster? No, unless you’re dealing with extreme humidity levels. Plaster needs humidity to dry right. If you quicken the process, it can lead to cracks, reducing the quality of your plaster application. It’d be best to maintain the humidity between 60% and 70%.

About the author

Sharif Hasan

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