Evaluation of an existing structure is accomplished by applying engineering principles with experience. CMS has over 50 years experience in evaluating in- situ structural conditions. Visual observations are initially made, span and load conditions determined, and evaluation of available strengths calculated. Available strengths are compared to the applicable service loads, as dictated by applicable building codes, service conditions, or deflection limits. Testing may be required to determine strengths of the in-situ structural materials. Testing may consist of destructive testing, ultra sound, x-ray, or chemical analysis. Some field conditions may require selective demolition to observe precise field conditions. Structures are subject to environmental conditions such as moisture, temperature, insect and chemical attack. Non-treated wood is extremely susceptible to deleterious moisture conditions which can promote rot and change internal moisture content of the wood, thus affecting strength. Concrete exposed to the environment is susceptible to reinforcement oxidation. This susceptibility to rust is dictated by moisture and the chloride content in the concrete. Older structures are particularly susceptible due to the fact that some of the admixture accelerators contained high chloride content. De-icing salts may also subject concrete to accelerated deterioration. Corrosion of the reinforcement steel in concrete causes the metal to expand and spall the adjacent concrete, losing bond and strength. Structural steel is also susceptible to environmental conditions from moisture and other corrosive agents. Not only will steel rust, it may also de-laminate under extreme, prolonged deleterious conditions. While galvanization prolongs the service life of structural steel, it remains a sacrificial surface that will break down over time. In addition, all structures are susceptible to loads beyond their available strength. Bearing, shear, and bending failures present a hazard to safe occupancy, and when discovered, demand immediate shoring, reinforcement and remediation.