Hello everyone!
We are in the process of replacing the ceiling in the basement of our summer house and have hired craftsmen to fix a lot of things. However, we have done some things ourselves and have now hit a snag. The ceiling is supposed to be insulated with loose fill insulation. For that reason, we need to put up boards and were recommended to use oil-hardened ceiling masonite. We have put up battens and last weekend my siblings were there and started screwing up the boards. When we went out yesterday and took a look down there, the boards have warped (see pictures). The boards are 6 mm thick. We don't really understand what we did wrong? Do we have the wrong side down? Thoughts? Grateful for any help we can get.
Best regards / Dante