By: Marek Patrosz
Deterioration is common to cementitious based building materials such as concrete, cast stone and stucco systems due to age and weathering, so the extent of repair frequently includes patch repairs and/or requires replacement.
When deteriorated conditions at cementitious based materials do not warrant full replacement or patch repairs, elastomeric coatings may extend the life of these building features. Elastomeric coating protects the surface and mitigates moisture infiltration. These coatings are cost effective, easy to apply, and highly versatile.
Elastomeric coatings are liquid-applied systems that can be a water based or acrylic latex-based. The viscosity of the coatings are typically ten times thicker than the average application of exterior grade paint. A coating system can be breathable to allow moisture to be released from the substrate while preventing carbon dioxide and water from penetrating the exterior surface. The coating thickness and elasticity helps protect cementitious surfaces with hairline cracks that are subject to dynamic movement – especially in the northeast where significant temperature swings can cause building materials to expand and contract on a daily basis. Elastomeric coatings can easily be applied in thick coats with a paint brush or roller and may be installed vertically and horizontally. Once applied, the coating bridges micro cracks up to 1/16” thick as well as minimizes carbon dioxide, water, and chloride ingress. The protective attributes of elastomeric coatings are complemented by its ability to enhance or match the existing colors and textures of a building. This is especially beneficial when a project team must conform to strict aesthetic requirements, such as when working with the NYC Landmarks Preservation Commission on buildings that are designated landmarks or are located in a historic district.
There are several factors that must be accounted for when considering an elastomeric coating for building components. The process begins with verifying that the existing cementitious components are structurally sound and cracks no larger than a hairline width are present at the surface. All surfaces to receive the coating system must be cleaned in order for a strong adhesive bond; a cleaned original surface is also beneficial for a true color match, if that is required. The elastomeric coating must meet the state and/or federal volatileorganic compound (VOC) requirements. Water-dispersed and acrylic-based elastomeric coatings are well-suited for dynamic movement. Once a product is selected, a test sample is necessary to verify an aesthetic color match of the coating within a cleaned area of the existing substrate prior to a full application.
The elastomeric coating application can typically last 2 to 5 years, depending on the quality of the product system, the severity of pre-existing deterioration, and the exposure to weather or caustic atmospheric conditions. If the coping stones, stucco coatings, or decorative stones on your building are beginning to show hairline cracks or signs deterioration from acid rain, elastomeric coatings may be a prudent option to extend the life of these elements until a full comprehensive repair or material replacement is required.