Siding As a Rain Screen

What Is a Rain Screen?

• A rain screen is a moisture-management system placed on the exterior of a house. The rain screen consists of an exterior siding, often an airspace beneath the exterior siding and then a separate barrier with flashing that prevents water from reaching the construction paper wrapped around the house. These moisture-management systems prevent water from damaging the wooden interior structure of the house.

Types of Siding

• Many different types of siding exist. Among the most common types of siding are brick and vinyl. During rainy weather, most water runs off of vinyl siding, but some rain can flow into the J channels underneath siding panels. Brick veneer siding absorbs water through mortar joints, which then needs to be drained from behind to prevent damage.

Pressure-Equalized Space

• Because brick veneer siding absorbs moisture through its joints, a pressure-equalized space must be used beneath the external cladding. The space beneath brick veneer is usually 1 or 1.5 inches deep. Weep holes are installed at the top and bottom of the siding, equalizing the pressure inside the wall. This pressure-equalized space prevents water from seeping into the house and allows rain and moisture to run down the house and back into the ground. Weep holes may be covered by a grate, netting or even a water-absorbing rope that prevents pests from entering the home.

Flashing

• To provide additional protection to the house beneath the siding, flashing is used beneath brick veneer and on homes with brick veneer and vinyl siding combined. Flashing is made from flat sheets of metal that are nailed to the sheathing near the bottom of the house, beneath windows and in transition areas where siding and veneer meet. Flashing safely guides rain and moisture away from the house and into the ground.

Weather-Resistant Barrier

• Protecting the construction paper wrapped around the house -- beneath brick veneer and vinyl siding -- is a weather-resistant barrier that works like flashing to prevent water from seeping into the house. Often these barriers are made from high density polyethylene. Heavy-duty barriers may have their own pressure-equalized space within it. These heavy-duty barriers are used in climates that see heavy rain and wet conditions over the course of the year.