Three layers of stucco are used in every stucco building. The principal layer is the scratch coat. The earthy-colored or brown coat layer is the succeeding layer. Then comes the last top layer, stucco coat, which can be shaded or painted with colors. The stucco coat drying process is solely subject to the drying of the brown-colored coat. For appropriate drying of the last layer, the second layer must dry properly in the first place. Actually, each coat should be permitted or given the needed time for the water in its blend to evaporate.

Sometimes, after a few days of installation, the surface of the exterior stucco or top layer may feel firm on touching. But it doesn’t signify that the stucco is dry. 

The water in the stucco blend should release gradually for appropriate drying. If every one of the components cooperates as they ought to, the normal drying time for the stucco is 90 days. Don’t go for pressure washing, or any other kind of cleaning during this multi-day, 90 days, time frame, so you don’t cause harm to the stucco. After 90 days, it will be immovably set.

How does stucco dry?

As you already know, stucco is a Portland Cement-based product and counts on the water in the blend responding with the cement. The cement absorbs the water as the reaction takes place, which causes an “Exothermic” event and leads to the binding of the aggregate and sand. In this way, the artificial rock, which we also know as concrete, forms.

The hydration process consumes most of the moisture and some of the moisture vanishes away with the evaporation process. Thus, the stucco gets cured properly. However, premature hydration may fail the curing process and lead to the shrinkage cracking of the stucco. 

Stucco absorbs moisture again from rain or high humidity. So, if you allow such moisture in or out of stucco, it will lead to a dozen problems in the long run. There will be “Alkali Burn” and it will blister and delaminate the coatings. So, paint the stucco, seal it, make it waterproof as early as possible.

What Affects the Drying of Stucco?

There are a few things that directly affect the drying process and time of stucco. Let’s see how the affect:

Brown Coat:

Both the brown coat and stucco coat are very significant to each other and they share some similar characteristics as well. Take water mixing, for example. Both the coats require to be mixed with a certain amount of water in the process. They need to be mixed for the same period and applied in the same time span.

On top of that, both these coats must be as identical as humanly possible while installing. Thus, the rate of drying will be the same for both the coats, so will be the drying time.

Humidity:

When it comes to stucco drying, the moisture level of both the stucco mix and the atmosphere is one of the primary concerns. The chemical reactions that occur within the Portland cement mix in stucco applied to the exterior walls are solely affected by water. Here water works as an engine to drive the chemical reactions for drying the stucco properly.

1. Dry atmosphere: Dry atmosphere pulls out the water from the stucco mix and all three layers very quickly resulting in a fragile stucco installation.

2. Cool and damp or cloudy atmosphere: In such weather conditions, the stucco neither dries quickly, nor takes too much time to ensure proper drying. So, it is the best weather condition for stucco drying.

3. Rain: You have to keep the stucco damp, yet if the rain wets the stucco in an unplanned way, it is not good for drying. Rather it results in incapacitated, outrightly vulnerable, and delayed stucco delamination.

Temperature:

The ideal outside temperature range for proper drying of stucco is between 4 to 32 degrees Celsius (40 degrees Fahrenheit to 90 degrees Fahrenheit). So, the best time for installing exterior stucco is throughout the entire summer and in the early autumn. 

Remember, the temperature needs to be the same in both the period when applying the brown coat and when applying the stucco coat. Temperature impacts the moisture content in these coats in the same way. Eventually, the amount of moisture content affects the drying process and time.

Can new stucco get wet?

Yes, the new stucco needs to get wet. But it should not get wet because of the rain. Consequently, the ideal weather condition for stucco installation is neither a sunny day nor a rainy day, rather it needs to be merely a cloudy day. 

If it is a sunny day, the stucco will dry too quickly resulting in cracks in no time. So, to ensure the stucco dries ideally and gradually, keep the stucco damp. Mist the stucco using water from time to time.

How often should you wet new stucco?

To supply additional curing moisture to the stucco, you have to wet stucco periodically throughout the day. Usually, wetting the stucco a two, even one time a day would suffice. The first two days after installing the stucco are very critical. So, in severe conditions, it is important to utilize the sun and windbreaks to provide the stucco with extra protection from the elements.

How long should stucco cure before the rain?

According to the stucco manufacturers, the typical moist-curing time is a minimum of 48 hours. But when the humidity is around 80%, one should not go for the moist-curing phase. There are two widely accepted and most effective methods for curing stucco. One is the double-back method, and the other is the surface-misting method, which is also known as the fogging method.

 If one of the methods is applied, the stucco will get firm before it rains. But if it rains, before this period is finished, the chemical bond of stucco will face stress and stucco delamination will be delayed. Besides, the bond between different substances of stucco will remain incapacitated and outrightly vulnerable.

How long should you wait between stucco coats?

According to the stucco and siding experts, it is very significant and beneficial to the stucco to ensure a stronger bond between the two coats and give it some time to secure enhanced curing of the coats. Especially, the scratch coat or the first coat needs to be cured completely before setting up the second coat. 

Then comes the brown coat that needs to be cured for a minimum of 7 days before applying the last coat, stucco, as per the UBC and IBC. On the other hand, the NWCB suggests curing of a minimum of 10 days.

Does stucco need to be sealed? 

Yes, stucco needs to be perfectly sealed every 5-8 years to prevent moisture intrusion. Usually, silicone-type sealers are used to seal stucco. If you seal the new stucco using masonry sealer or clear concrete, it will penetrate into stucco siding very easily, which will eventually prevent moisture intrusion and keep your stucco safe in the long run.

Should you wet stucco before painting?

You should not wet stucco before painting. Rather you have to dry the stucco adequately before you can apply any paint to it. 

However, during the drying process, it is essential to wet the stucco from time to time to pull the excess lime out. If you try to rush the curing process in any way, the curing process will not be finished properly. This will result in the rapid deterioration of the exterior stucco. So, clearly, painting the stucco right away after wetting is never an ideal option.

So, although the normal drying time for the stucco is 90 days, it is dependent upon various factors and weather condition. Pay close attention to the weather conditions and other discussed factors above and take the needed measures to ensure long-lasting stucco.

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