No, in general it will not be damaged. The Groasis Waterboxx® plant cocoon is designed in such a way that the expanding ice is able to find room to expand. This is done by designing the inclination of all the vertical sides in 8°C. So when the water expands to ice between +4°C to -1°C (+39,2°F to +30.2°F), the ice can just go a bit higher - pushes the cover off the box - and find room for expansion. Sometimes there is a heavy layer of snow on top of the cover and it cannot be pushed upwards. If coincidently the water is on its highest level while turning on ice, then in those occasions you may find some broken covers. It is also important to understand that it doesn't matter whether it is -1°C (+30,2°F) of -30°C (-22°F) . Once changed from water into ice – which happens between +4°C and -1°C (+39,2°F to +30.2°F) - the ice doesn't expand any further.