Winters in Japan’s Tohoku region are particularly harsh. Metal sheet roofing, valued for its ability to shed snow and withstand heavy snowfall, is a familiar feature of homes across the region—a reflection of the local climate and way of life. Yet heavy snow and ice place considerable demands on the coatings that protect these roofs. How has Nippon Paint responded to these challenges and the needs of professionals on the ground? Here, we explore the development of coatings tailored to local conditions that have earned lasting trust while helping preserve Tohoku’s beautiful streetscapes.

A Durable Coating Developed for Tohoku’s Harsh Winters

Metal sheet roofing is widely used in some of Tohoku’s coldest areas, including Aomori, Akita, Iwate, Yamagata, and the Aizu region of Fukushima. Concrete tiles and slate-style roofing can absorb moisture, which may freeze and expand, causing cracks. Metal roofing does not absorb water and is relatively lightweight—an important advantage in areas where heavy snowfall places additional loads on buildings. These qualities have made it a trusted choice for homes across the region.
The region’s harsh climate also places considerable demands on metal roof coatings. In winter, snow accumulates on roofs, melts during the day, and freezes again at night. As snow and ice slide off, they subject the coated surface to substantial wear. A durable coating film that can withstand these conditions is essential. Appearance is equally important. In the metal roof repainting market, customers favor a high-gloss finish with a rich, full-bodied appearance. Roof coatings must therefore combine an attractive finish with the durability needed to withstand the region’s severe winters.

Addressing Painters’ Challenges: Improving Workability and Adapting to Temperature Changes

Painters faced practical challenges on site as well. Slow-drying coatings could leave the surface vulnerable to footprints when painters returned to apply the next coat. Feedback from the field highlighted the problem: “The coating surface stays tacky, so we can’t get back on the roof,” and “We need a coating that dries faster.” Another common concern in Tohoku, where temperatures can fluctuate sharply, was “blushing.” When a coating is exposed to nighttime dew before it has fully dried, moisture can disrupt the film’s surface, leaving it rough and giving the finish a dull or whitish appearance. Addressing these challenges became a key driving force behind the development of a new coating.

Balancing Fast Drying and Rich Gloss to Develop a Trusted Choice

In the early 2000s, our Silicon Roof metal roof coating lagged behind competing products in drying speed, gloss, and durability. Responding to feedback from painting professionals, our Tohoku branch led the development of a new product in collaboration with the marketing and development teams. The key challenge was to combine fast drying with a rich, high-gloss finish. Achieving both required a careful balance: enhancing gloss could slow drying, while accelerating drying could make surface irregularities more visible and compromise the finish.
To address these challenges, the development team formulated a new resin that dries and cures quickly while providing lasting durability. They also fine-tuned the formulation to achieve a rich, full-bodied finish and control the curing process, conducting repeated testing and refinement in the laboratory and at a painting sites. The result was Silicon Roof II. Its faster drying helps painters work more efficiently, while its smooth coating film enhances gloss and helps roofs retain their snow-shedding performance over time, reducing the need for frequent repainting. Today, its affordability and ease of application have made it a trusted choice for metal roofs across Tohoku.

Slowing Deterioration for a Smoother, More Beautiful Finish

As Silicon Roof II gained wider use, painting professionals called for even greater durability and a more attractive finish. In response, we adapted the radical control technology used in Perfect Top Si, a popular exterior wall coating, for use in roof coatings. Exposure to oxygen, moisture, and ultraviolet light can generate highly reactive substances known as radicals within conventional coating films. These radicals break down the resin, accelerating deterioration. Our technology helps protect the coating film by suppressing radical formation and neutralizing radicals that do form.
We also focused on creating a smoother coating film. Surface irregularities scatter light, making it difficult to achieve a clear, high-gloss finish.
The development team conducted repeated tests under conditions that replicated intense summer heat, including roof temperatures of up to 80°C. On-site trials throughout the winter also verified the coating’s resistance to peeling. Drawing on these results and feedback from the field, the team developed Fine Perfect Roof, our premium roof coating. The combination of deterioration-control technology and an exceptionally smooth surface that minimizes light scattering delivers enhanced durability and a rich, high-gloss finish.

Creating a High-Gloss Finish Through Viscosity Control and Surface-Smoothing Technology

Gloss depends on how light reflects off the coating film. The more consistently a surface reflects light at the same angle, the greater its gloss, while surface irregularities scatter light and diminish gloss. Viscosity control and surface-smoothing technology help the coating level as it spreads, forming a smooth, even film. Fine Perfect Roof combines these qualities with ease of spreading, helping painters achieve an attractive finish with greater ease.

Evolving with Local Needs, Bringing Color to the Region

Today, the two products meet different needs on site. Silicon Roof II offers fast drying and cost-effectiveness, while Fine Perfect Roof delivers a superior finish and enhanced durability. Together, they allow us to recommend the most suitable coating for each customer’s needs. “The more coating we sell, the more beautiful the town becomes.” Guided by this belief, these products continue to protect homes through harsh winters in Tohoku and other cold regions. By listening to local voices and continually refining our products, we will continue to bring color and lasting beauty to Tohoku’s streetscapes.

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