Using vertical siding on the exterior of a home is an inexpensive way to add character. This design style remains especially popular in the Midwest, Northeast and increasingly in the South. At the same time, more contemporary housing designs are using vertical panels rather than traditional lap siding.

Whether traditional or modern, vertical siding can quickly become a breeder of mold and rot — unless builders know how to install it with proper moisture management.

Here are four of the most common water barrier mistakes builders need to avoid when installing vertical siding.

1. Butting panels together. Vertical siding is made up of a series of panels that join together. But wherever panels meet each other horizontally, they need z-type flashing to prevent water penetration behind the siding. Flashing also provides just enough of a gap to give moisture a way to escape from behind the cladding.

2. Butting battens together. Traditional vertical siding using battens to cover the seams between panels. Many builders simply butt battens together on longer seams. But even this small horizontal gap creates another way for water to penetrate. Instead of butting battens together, builders need to join them with a 45-degree angle cut that prevents water from penetrating the batten. Be sure the angle drains “down and out.”

3. Failing to provide drainage. Even using the aforementioned techniques won’t guarantee complete moisture protection. So the best insurance against mold and rot is installing a proper drainage plane behind the siding that will drain moisture away from the structure. The Building Enclosure Moisture Management Institute (BEMMI) says areas with 20 inches to 40 inches of annual rainfall should use enhanced moisture management — drainable wraps or drainage mats. Drainable wraps incorporate both a water resistive layer and drainage gap created by spacers. These gaps help water drain from behind the cladding at a faster rate. BEMMI says areas with 40 inches or more of rainfall require water resistive barriers plus rain screens, which not only protect against water intrusion but also offer drying capabilities.

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