Three-Coat vs. Two-Coat Paint Systems for Buildings

More is better, right? For many architects and building owners, the decision between three-coat and two-coat paint systems isn't straightforward.

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What’s the Difference?

As the names suggest, one system includes three layers of coating, while the other has two.

A two-coat system generally has a primer and a topcoat. Conversely, a three-coat system adds a clear coat on top of the other two layers.

While the difference might seem minor, it has broader implications. Two-coat systems can be processed in a single pass through the commercial coil coating lines, whereas three-coat systems often require a second pass.

Additionally, two-coat systems are standard for most manufacturers. In contrast, three-coat systems are usually special orders, impacting both cost and lead times.

Are 3 Coat Systems Necessary?

For most colors, a two-coat PVDF system is sufficient. However, a three-coat PVDF system—comprising a primer, color coat, and clear coat—can enhance color retention and chalk resistance for saturated colors.

Colors like reds, oranges, and purples benefit from a clear coat. Similarly, some metallic colors, such as bright silvers, require a clear coat to prevent aluminum flakes from darkening.

Outside these cases, three-coat systems are rarely necessary.

Lead Times & Minimums

As mentioned, three-coat systems are special orders, leading to longer lead times and minimum quantities. This can be an issue for replacements or small quantities needed later on.

Material Cost

Material cost is always a consideration. Two-coat systems are cheaper because they only require one pass through the coating process. The additional cost for three-coat systems can be due to raw material costs and the need for a second pass through the coating line. Higher reject rates and extensive line clean-up also increase costs by 300-400%.

Given these added costs, the decision for a three-coat system shouldn’t be taken lightly.

Performance

Three-coat systems don't offer better warranties, indicating similar expected performance compared to two-coat systems.

A Sherwin Williams technical representative summarized that clear coats either notably improve a coating’s performance or make no difference. Three-coat systems can benefit saturated colors, but for most earth tones, they're unnecessary and increase costs.

Harsh environments might see slight benefits from the extra thickness of a three-coat system. However, limited data supports this, making the decision still quite gray.

Color Selection

Architects often choose three-coat systems to access a broader range of colors. However, many manufacturers offer metallics in a two-coat system, making three-coat systems an unnecessary expense.

Specification Tips

If the goal is to access a full color selection, including metallics, specifying “manufacturers full standard colors including metallics” can avoid unnecessary costs.

Most manufacturers offer at least one standard red color. Purples and oranges are rare, so they should be specified as a “custom color 3-coat system” for accurate project bidding.

For performance in corrosive environments, write the base bid as a two-coat system with an alternate add for a three-coat system to understand the true cost increase.

Summary

The first consideration for a two-coat vs. three-coat system should focus on intended colors. For saturated colors like purples and oranges, specifying a three-coat system might be prudent.

For most applications, a three-coat system offers minimal performance gains and doesn't justify the additional costs and lead times.

Considering the intended color, budget, construction schedule, and environmental harshness will aid in decision-making. While decisions won’t be black and white, understanding two-coat vs. three-coat systems makes them less gray. If you need more help, feel free to reach out to us!

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