There are many situations. First, the main keel and auxiliary keel of smallpox are uneven, and the modeling gypsum board is uneven; Second, the quality of gypsum board itself; Third, there are too few nails when sealing gypsum board, and the interval is too large, resulting in uneven stress and ups and downs; Four, smallpox batch of hand-painted latex paint is not good, when plastering is uneven, sandpaper is not good, forming ripples.

Cause analysis: ① Arbitrary arching leads to uneven camber; (2) The grid or edges around the ceiling are uneven; ③ The high moisture content of wood leads to shrinkage and deformation; (4) The keel joint is uneven and hard to bend, resulting in uneven ceiling; ⑤ Derrick or derrick spacing is too large, resulting in irregular deflection after keel deformation; ⑥ The wooden boom head cracked, and the keel fell after being stressed; ⑦ When the steel bars are used as suspenders, they are not tightened, and the keel falls after being stressed; ⑧ The derrick is hung on the bracket of other pipelines or equipment, and the ceiling is uneven due to vibration or bracket falling; Pet-name ruby stress nodes combined with lax, displacement and deformation after stress.

Precautionary measures: the ceiling should be made of high-quality wood, such as pine and Chinese fir, and its moisture content should be controlled within 12%. Keels should be straight, and there should be no cross-sectional knots. Ceiling construction should be leveled according to the design elevation of the peripheral wall, and the horizontal line should be subject to the surrounding of nail installation. The springing height of the indirect horizontal line is 1/200 of the short span of the room, and the longitudinal springing should be hung evenly. The stressed joints should be nailed tightly and firmly to ensure the overall stiffness of the keel.