Depending on the type of the load which affects the durability and design life glass fibre reinforced polymer (GFRP) structures should be designed so as to take into account as first of all the chemical-physical conditions in which the structure is used including: ultraviolet (UV) radiation, temperature influences, humidity, water and chemicals. The results presented herein provide a predictions regarding of the mechanisms involved in the ageing of GFRP pultruded bridge profiles and predicting the property micro scale changes with time and remaining service life of GFRP under real environmental degradation impacts and during simulation laboratory conditions. The outermost layers of FRP (fibre reinforced polymer) composites are damaged mostly because of UV radiation. Radiation also induces remarkable microstructural changes depending on wavelength and intensity, and oxygen availability, eventually leading to polymer chain scission. A scanning electron microscope (SEM) was used to investigate the degradation mechanism of the GFRP samples subjected among others to UV radiation and water vapor condensation. Glass fibre-reinforced polymer GFRP pultruded profiles have great potential in the construction industry, presenting several advantages comparing with traditional materials, among which, the potentially improved durability under environmental influents.