Epoxy And Polyurethane Crack Injection

When you need to repair a crack in your foundation and don’t want to dig up the foundation wall, you should know that there are two ways to fix cracks from the inside: epoxy injection and polyurethane injection.

Comparison of the characteristics of epoxy and polyurethane

Epoxy and polyurethane are referred to as resins; for the most part, both are two component formulations. The blending of the 2 components for each resin type creates a material with the requisite properties for professional crack injection repairs.

In the case of epoxy, one component is the epoxy resin and the second is a hardener; both are blended together immediately before a crack injection. The mix ratio is typically 2 parts epoxy to 1 part hardener. Most injection epoxies fully cure within 3-4 hours at a temperature of 77° Fahrenheit or 25° Celsius; although some faster curing epoxies have recently been introduced. Epoxy is comparable to glue; once cured, it has a strong bond and a hard plastic-like texture.

Polyurethane (or urethane), used for foundation crack repair applications, while not necessarily a 2 component blend, can have 2 components; the polyurethane resin and an activator, or accelerator. Like epoxy, the 2 components are mixed before they are injected into a foundation crack. Unlike epoxy, the texture of cured polyurethane can vary significantly as there are many different polyurethane formulations in use.

Like epoxy, polyurethanes have varying viscosities (thickness of the fluid) depending on the formulation used. Some cured polyurethane formulations become very rigid, some are powdery, others are rubbery, etc. The polyurethane formulations vary among manufacturers so one cannot generalize regarding the properties of cured polyurethane. To accommodate crack tension and compression we believe that polyurethane should cure with a rubber-like consistency. The cure time associated with polyurethane does vary, even among crack injections using the same formulation. The initial cure time for polyurethanes is generally 15 – 45 minutes and is influenced by both temperature and moisture.