All perimeter sealants do not react the same when exposed to long term UV and extreme heat caused by the environment. The resistance to weathering is achieved by the inherent nature of the sealant polymer system. Some manufacturers achieve some degree of resistance to weathering by the use of fillers which shade the polymer from the UV and others use chemical additives to absorb the UV radiation and protect the polymer system. This paper will look at combinations of deteriorating mechanisms and give some indication as to the key factors causing the deterioration or sealant changes with the sealants studied. Some urethanes were shown to revert back into their original liquid state during UV exposure where the silicones did not. By the use of accelerated weathering lab equipment and lab ovens, the detrimental physical effects were demonstrated on various two-part urethane and one-part silicone perimeter sealants currently used in construction. Tensile adhesion data, durometer and visual observations are reviewed following a specific exposure time. This testing evaluation showed a faster sealant degradation with heat and ultraviolet light when compared to cyclic UV and condensation cycles with UVB313 bulbs. No significant degradation occurred with samples exposed to 100% humidity at 30°C (86°F) or 50°C (122°F) with the exception of loss of adhesion to the precast concrete. This study provides the framework of a test method to screen perimeter sealants for durability and reversion resistance.