Blog

Whether fiber cement T&G planks are “factory-sealed on all six sides” depends entirely on the specific product line and manufacturer. This is a critical distinction because it determines the board’s lifespan and the amount of work required on-site.

1. The Three Common Sealing Levels

In the industry, you will typically find three levels of factory treatment:

• Unsealed (Raw): These are light gray and have no coating. You must prime and paint all six sides yourself before installation. This is becoming rare for T&G products due to the difficulty of painting inside the groove on-site.
• Pre-Primed (Most Common): The boards are coated with a factory-applied primer (usually white or gray). High-quality brands will seal all six sides, including the tongue and the internal groove, to prevent moisture wicking.
• Fully Pre-Finished (Premium): These come with the final color (or wood stain) already applied. These are always sealed on all sides.

2. Why Sealing the “Tongue and Groove” is Critical

The T&G joint is the most vulnerable part of the cladding system for two reasons:

1. Capillary Action: If the inside of the groove is raw cement, it acts like a straw, sucking in any moisture that manages to get into the joint. This leads to edge swelling and paint peeling.
2. Hidden Protection: Once the boards are clicked together, you can no longer reach the joint with a brush. If they aren’t factory-sealed, the most sensitive part of the board remains unprotected for the life of the building.