Structures Unlimited enclosures and skylights for municipal water and waste treatment facilities can save money and time while helping control the process environment. Each Structures Unlimited enclosure is a light-transmitting, insulated building that is completely factory designed, engineered and prefabricated. Pre-insulated and pre-finished, inside and out, means the building can be used as soon as it is fastened in place. All the materials used are super-strong, non-corrosive, moisture and chemical resistant and virtually maintenance free. The enclosure system is fabricated of tubular aluminum box beams and is erected with internal connections.