Toaroha Schist is a type of metamorphic rock found in New Zealand. While it is generally suitable for exterior applications, its performance in very humid climates may depend on various factors such as the specific location, maintenance, and finish applied to the stone.

In humid climates, the presence of moisture can potentially affect the durability and appearance of natural stones. Excessive moisture can cause certain types of stone to deteriorate, discolor, or create conditions for mold and mildew growth. Therefore, it is essential to consider the specific conditions and take appropriate measures to ensure the longevity of Toaroha Schist in humid climates.

To mitigate potential issues, the stone should be properly sealed to protect its surface from moisture absorption. A high-quality sealant will help to reduce the risk of water penetration and minimize the effects of humidity. Regular maintenance, such as cleaning and resealing, may also be required to ensure the stones performance in a humid environment.

It is advisable to consult with a local stone supplier or a professional architect who has experience with natural stones in humid climates. They will be able to provide specific guidance on the suitability of Toaroha Schist for your project and recommend appropriate treatments to enhance its performance and durability in such conditions.