Most of people normally hear the strange noise on the roof sheet but do not know where it’s come from. It is hard to stop thinking about the noise and some time it causes the sleepless or even praying for a good sleep.
It is normal that the construction materials will make some noise. During the day time, the steel structure will expand and during the night time, it will contract which can cause some noises including a roof sheet made from steel. The noise not only come from the roof sheet itself but also from the accessories or screws or even the wooden floor also causes the noises as well. The majority of the noises are from the thermal expansion and contract of the construction materials.
Nevertheless, noises are the nature of construction materials, no need to worry too much. It does not cause any dangers and does not affect to the structure, just keep calm and have a good long sleep.