How Long Does Waterproofing Take To Dry?

How Long Does Waterproofing Take To Dry? The longevity of waterproofing is dependent upon the time it takes to “dry.” When a new coat of paint or compound is applied, the top surface of the material absorbs moisture from the air. This moisture must evaporate for sufficient adhesion to occur between successive coats and effectively achieve long-term resistance to water penetration.

Several factors affect drying rate: climate (humidity), temperature range, degree of overbuilding, percentage solids vs. thinning ratio, size and shape of the painted surface, primer type, and consistency. These variables have been categorized into three broad categories as they relate to their influence on drying rates:

Climate

High humidity conditions typically slow down evaporation by reducing the rate at which moisture can evaporate. Humid conditions, particularly during high temperatures (90°F and above), are viewed as the most significant factor for lengthy drying times.

Temperature range

The temperature of the paint job will influence drying rates. A cooler temperature range (<70°F) typically increases drying time, whereas warmer ambient temperatures decrease it. Low or warm temperature conditions are observed to cause lack of adhesion, premature curing, low film strength, and excessive checking with some multi-component products.

These factors result in very long dry times and frequent recoat intervals required for a complete cure with one-component sealers such as skylight 5100. Some two-component sealers like polyurethane have lower potentials for checking and adhesion failure even at warmer temperatures.

Degree of overbuilding

The amount of waterproofing material applied to the substrate will influence drying time. Excessive build or “topping” in one-component products can ultimately cause poor performance, as with multicoat situations described earlier. A high solids content also slows down drying times as the water is better able to dissolve the resin before it evaporates through film expansion.

This will cause gassing off, excess flashing, pinholes, and bubbles until a full cure is achieved. Some two-component products have sufficient catalyst systems that allow for increased dry times if necessary to accommodate these conditions where flash curing may occur due to excessive moisture absorption from evaporation delay by a layer above it that does not have catalyst.

Percentage solids vs. thinning ratio

Solvent-based products are thinner than waterborne products, making vapor drive a desirable property with newer waterborne formulations that use less volatile organic compounds (VOCs). Thinning will increase the evaporation rate and thus decrease drying time. However, a lower solids content can result in poor adhesion.

Low shear or viscosity is also key to allow for thorough wet-out before solvent evaporation. Waterborne sealers typically take longer to dry as they rely on less volatile materials for curing, but the fact that these formulations don’t require drying aids or heat during application allows for more flexibility in thickness distribution and, as a result, faster overall drying times.

Size and shape of the painted surface

Surfaces with a large area to be coated may have significant effects on drying time, especially when high humidity conditions are present. High humidity levels combined with areas that require extended dry times due to excessive overbuild will extend dry times considerably in these circumstances.

The distance from the original point of application and the temperature range at each point during the cycle also plays a crucial role in determining the overall speed of drying. (see graphic below) A layer can absorb moisture laterally, but it cannot escape or evaporate until all layers above it are cured enough to allow for vaporization through capillary action from adjacent layers.

For this reason, a relatively thick film should be applied initially at slow speeds to thorough wet-out and then built up with successive coats at a faster rate to avoid excessive flash cure. It is necessary that the material not form high spots or bridges during application. Otherwise, each spot will take longer to dry due to lower vapor drive, which can result in uneven drying time.

Application methods

Wet spray application may allow for quicker dry times if the product does not contain additives such as pigments or fillers that increase viscosity and retard flow through airbrush needles, nozzle tips, and filters.

High humidity levels make evaporation difficult, so it may be advantageous to use forced hot air blowers/dryers on larger surface areas rather than waiting for higher rates of natural evaporation where high moisture content is still present in the curing substrate. This method can also be used in combination with forced air from a compressor or fan to supplement drying rates further.

Thickness of film

Thicker films take longer to dry naturally due to higher heat capacity and increased convection currents at the surface, which decreases the overall evaporation rate, except in regions of direct airflow.

By placing a barrier between surfaces and forcing air across the coating, it is possible to increase overall airspeed over these areas and thus increase evaporation rates in those zones when combined with high humidity conditions.

However, care must be taken not to dehydrate substrates excessively while using this method as it may have adverse effects on adhesion or component compatibility issues such as solvent bleeding where moisture levels are high, and evaporation has been substantial.

Humidity level

A higher ambient humidity level will reduce the drying rate through a temperature dependence effect on vapor pressure. High humidity levels combined with large areas that require extended dry times due to excessive overbuild will extend dry times considerably in these circumstances.

The distance from the original point of application and the temperature range at each point during the cycle also plays a crucial role in determining the overall speed of drying. (see graphic below) A layer can absorb moisture laterally, but it cannot escape or evaporate until all layers above it are cured enough to allow for vaporization through capillary action from adjacent layers.

For this reason, relatively thick films should be applied initially at slow speeds to thorough wet-out and then built up with successive coats at a faster rate to avoid excessive flash cure. The material does not form high spots or bridges during application.

Otherwise, each spot will take longer to dry due to lower vapor drive, which can result in uneven drying time.

Increasing surface temperature

Higher extensional viscosities for products containing fillers and pigments will increase the time required for curing in low humidity conditions because of increased evaporation rates through an inverse relationship between moisture content and solids loading.

This is also true when using coarse particle size additives such as glass fiber, chopped strand mat, or glass beads that cause additional shrinkage stresses, which may lead to uneven if not complete separation of the cured layer, resulting in flash cure and low thickness control.

The evaporative forces generated by these additives can be viewed as positive from a detailing standpoint because they assist in preventing aggregation when applying clear coats over colored base coats.

How Long Does Waterproofing Take To Dry? – Conclusion

By understanding how long it will take for your waterproofing to dry, you can ensure that you get the product applied as soon as possible so that you can start to enjoy the waterproofing benefits. Depending on the type of substance used, most people will be able to have their surfaces protected within 24 hours after applying their first layer, and some even have less time than that, depending on which brand they choose.