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You cannot install clapboard siding on a bare, unprepared surface. Clapboard siding requires a clean, sturdy base made from plywood or similar materials, sometimes called backerboard. Then, it needs an underlayment or sheathing, a moisture membrane to help protect the exterior wall.

Note that sometimes clapboard siding is caulked as it’s installed for additional protection. We don’t suggest this: Caulking the siding can trap moisture inside the clapboards and lead to moisture damage over time. The siding needs some space to “breathe,” especially in rainy weather.

You may only need to repaint fiber cement siding every decade or so, but you should clean it every six to 12 months, depending on your local climate. First, wash with a garden hose or similar low-pressure device (not a high-pressure washer, which can damage the material) to remove dirt and any large debris. Then, gently wipe down the surface with a soft brush or cloth in a side-to-side motion, following the grain of the fiber cement.

Some homeowners use caulk on the edges of clapboard siding to help seal it. However, this method invites new problems. With so many gaps sealed, clapboard siding is often unable to drain properly and moisture from rain or other sources can build up inside. This can lead to rot and other issues over time. When repairing clapboards, it’s best to avoid caulking the final product. The exception is trim around windows and doors, which should be caulked to avoid moisture problems.

There should be small gaps between your roof and the walls of your home, and other buildings. These small gaps let building materials shift, expand, and contract with weather and other outside forces, and they prevent moisture from wicking down walls from roofing and gutter systems. Without these strategic gaps, your home’s exterior and its finishes can sustain water damage, decay, peel, delaminate, and crack. However, there is a fine line between a smart gap and a problematic gap—all  gaps should be small, intentional, and covered or filled in with foam insulation to prevent pests from using them as access points.