When brick veneer is used as an exterior finish for an insulating concrete form (ICF) home, a cavity wall is recommended to manage moisture penetration.
The top of the concrete foundation wall below the veneer must have a width that is at least as great as the width of the abovegrade concrete wall plus the thickness of the foam layer outside it, 1 to 2 inches for an air space, and at least 2/3 of the thickness of the brick.
The foundation wall may be of the required thickness all the way up, or it may be narrower at the bottom and flared at the top to the necessary thickness to carry the brick. When a flared wall is specified, the angle at the point where the wall begins to widen should not exceed 30 degrees. Many form manufacturers offer convenient brick ledge forms to create the required flare at the top of the wall. A flared ledge section must be reinforced properly with a line of horizontal rebar, and stirrups between the horizontal bars in both the ledge and the wall as specified. This reinforcement must be sufficient to support the full weight of the brick veneer, which is typically more than 1000 pounds per lineal foot for a 25-foot height of brick.
Continuous flashing should be placed abovegrade at the base of the wall to divert any water to the exterior. Through wall flashing should extend vertically up the foam face of the wall a minimum of 8 inches. When possible, the flashing should extend beyond the face of the foundation wall to form a drip edge. Flashing pieces should be lapped at least 6 inches at any seams.
In order to drain water collected in the cavity, weeps are required immediately above the flashing. Spacing of the weeps is recommended at no more than 24 inches on center. An open head joint (formed by leaving mortar out of a joint) or wick and tube weeps are acceptable. Open head joint weeps should be at least 2 inches high.
Wick and tube weeps are permitted by most building codes to have openings a minimum diameter of 3/16 inch. Their spacing is recommended at no more than 16 inches on center. Wicks should be at least 16 inches long and extend through the brick, into the air space, and along the back of the brick. The elevation of flashing and weeps should be above planting beds, ground covering, and sidewalks that are placed immediately adjacent to the wall.
Brick ties connecting the concrete wall and the brick veneer should be embedded directly in the concrete or mortar of each. Ties must be regularly positioned at a spacing appropriate to the local lateral loads applied by wind or seismic activity.
— Shari VanderWerf is publications manager and Pieter Vander-Werf is president of Building Works Inc. (www.buildingworks.com), a consulting firm that helps companies introduce new construction products.