The steel roof and the sandwich panel are waterproof
The two are actually the same class of things, sandwich panels only the color plate and insulation layer together, the installation more convenient. And the pressure steel roof need to lay another insulation layer and the roof. For both, the weak links of water are between the plates.
In the actual project, the seam of the steel plate roof can be made in many forms, some of the overlapping form of waterproof performance is very good, and the common sandwich board roof shape is relatively simple, so the waterproof performance is also worse.
