CEMENT FIBER BOARD COLUMBARIUM APPLICATIONS
Columbarium Engineering Basics Series by Architarium

Cement fiber board, also known as backer board, is not intended to be used as a structural material, meaning one that can withstand multiple types of forces. It was developed to cover surfaces, not bear loads. Most often, it is used for water-resistant surfaces. In fact, it is also known as “shower board”. You can easily find it and examine it yourself in home improvement stores.

Strength: To some degree, cement board has compressive strength; i.e. it can withstand some downward pressure, most commonly weight. Of course, the resistance is also a function of board thickness. However, because cement board is rigid, it lacks the other mechanical properties of materials: torsional, tensile, shear and yield strength. These properties correspond to forces that are caused by impact, foundation shift, thermal expansion, winds, etc. Ironically, compressive force, created for example by a stone cap, will exacerbate stresses from these other forces in a columbarium. The same is true for thin and/or wet cement board. Because cement board columbaria are rigid structures, a force against an isolated area can simultaneously affect the entire structure or cracks can grow to eventually affect the entire structure.

Water: Cement board is deemed water-resistant, not water-proof. It is meant for moist, not wet, environments. For example, showers that use cement board should also use a water proof barrier. One cement board manufacturer specifically cautions against storing the product flat in an exterior location without a water-proof cover because water can pool and eventually penetrate the surface. Water can also enter through any cracks. Cement board has a tendency to wick water, once it has entered, as a result of capillary action. Water weakens cement board, which can be a problem when it is supporting a load from a stone cap, upper niches or urns. Water can also freeze inside of the cement board, causing fissures.

Mold: Correspondent to being deemed water-resistant, cement board is deemed mold-resistant. Where moisture exists, mold can exist. Subsequently, one of the most prominent cement board manufacturers explicitly excludes mold from its warranty.

Expansion: Cement board can expand with the presence of water or thermal activity. Such expansion can compromise joints, especially when adhesive is present.

Electrolytic Corrosion: This is a form of corrosion that occurs in metal that comes into contact with a base material like cement. As a result, a cement columbarium that uses metal hardware, supports or reinforcements can experience electrolytic action. All metals are susceptible to electrolytic corrosion. Even stainless steel hardware can experience galvanic corrosion when in contact with cement (or concrete).

Warranty: Cement board columbaria have some of the shortest warranties in the industry, as short as 5 years.

Cement board manufacturers have experienced class action suits for moisture issues in particular. If you consider a cement board columbarium, be sure to invest in a discussion with an engineering firm that specializes in materials engineering.