What about the ceiling?

It can be calculated according to the projected area or the unfolded area. If it is a linear reflective roof, it is calculated according to the developed area. The expanded area refers to the area of the ceiling obtained by adding the bottom surface (the distance from the ceiling to the roof) and multiplying it by the total length. The calculation of ceiling area is actually the calculation of gypsum board area. For example, 20 square meters is 4×5, and the calculation method is 4× (0.4+0. 1)+[(5-0.80).