How is stucco applied over insulating concrete forms (ICFs)?
Stucco is a popular and cost-effective finish. When placing plaster over ICFs, it is recommended to treat this substrate as any other sheathed system. It should include building paper, metal lath, and 3-coat portland cement plaster. In this way, plaster is properly supported, yet free to move independently of the substrate beneath it. Some ICFs contain embedded furring strips on their face. After placing paper over the face of the ICF, metal lath is mechanically fastened to the furring strips. The lath supports plaster and holds it in position while the paper isolates the plaster from the foam. ASTM C 1063, Installation of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster, provides guidance on the size of metal lath, number and length of fasteners, and appropriate spacing of contraction joints. Although plaster would adhere to the face of the ICF, the weight of the layer is more than should be supported by foam. The plaster could settle or shear entirel
