What Keeps Hardie Siding From Leaking?

Density

• Density is one of the key qualities of fiber cement siding like Hardie and other brands. The cement construction of this material makes it highly compact. The result is siding that is heavy and may be more difficult to install, but has excellent water resistance and will not easily degrade -- even in the face of harsh storms, or over time.

Proper Vapor Retarder

• The vapor retarder is the layer of plastic that is used beneath the siding in order to protect the inner wall layers against moisture. Depending on the type of Hardie board, an interior vapor barrier can help prevent moisture buildup and water damage through the siding. For thick fiber cement boards, drainage space in cold climates can help allow moisture to flow through the back of the siding without collecting and causing damage.

Caulking

• Cement fiber board needs to be properly caulked at the edges of the wall and the corners where it meets different layers of siding. There are exterior wall caulks designed with waterproofing capabilities and mortars with similar features that can help prevent water from leaking into the small cracks at the edges of your project. Careful caulking can save you costly water damage repairs in the future.

Proper Installation

• Proper installation refers to issues such as sizing and gap space. The Hardie brand of siding needs to be kept about 2 inches away from roof surfaces, decks, driveways and other types of material. It needs to be at least 6 inches above the finished grade of the house, and gutters need to be 1 inch away from the siding. You should not caulk the flashing above windows when using this siding, in order to prevent cracking issues.