Often watching wuxia films gives people the wrong impression, that great heroes only need to lift a roof tile to see the situation inside the house. In reality, this kind of maneuver, while not entirely utter nonsense, is not very feasible.
On a real roof, several layers of tiles are laid, not just one, unless it is a family too poor to afford many tiles. Besides, the tiles are not just suspended in mid-air; they are laid on a roofing structure made of mud plaster and straw. Lifting a tile would only reveal a layer of straw.
This is for waterproofing and insulation. Otherwise, if it drizzled outside, it would pour inside, forcing the whole family to go outside to take shelter from the rain. When Yang Yiyi saw the roof structure beneath the tiles, and even a few small insects crawling away, she was immediately at a loss.