12/12/2025
Did you know that T-111 siding is considered a weathertight panel and does not require weather paper behind it?
On the other hand, Hardie materials are not weathertight panels and must have weather paper installed behind them.
Lastly, composite panel materials—such as LP products—typically do not require weather paper unless you are installing lap-style products. However, it is generally a good idea to include weather paper behind composite materials for added protection.
-Keep in mind that all of these products come with installation instructions that establish the standards for how they should be installed at that time. And yes—the installation requirements for all of these materials have changed many times over the years.