This invention relates to a ceiling construction for buildings and more particularly, to an improved ceiling construction having a ceiling framework which comprises a plurality of main beams and a plurality of cross beams.
Within recent years, ceiling constructions erected by the exposed, concealed and dry wall construction methods have been popularized.
The ceiling framework of the ceiling construction erected by any one of the three known construction methods comprises a grid system which comprises a plurality of flanged main beams and a plurality of flanged cross beams interconnected at right angles to each other to form a grid formation. In the ceiling construction erected by the exposed construction method, the ceiling boards which constitute the ceiling wall are fitted in the grid and laid on the flanges on the main and cross beams in the grid. In the ceiling construction erected by the concealed construction method, the ceiling boards which constitute the ceiling wall are positioned in the grid with the flanges on the main beams received in the grooves formed in the end faces of the ceiling boards. In the ceiling construction erected by the dry wall construction method, the ceiling boards which constitute the ceiling wall are secured to the main and cross beams by means of nails or screws in the grid. The ceiling construction usually includes an access door, but in the ceiling construction erected by the exposed construction method, since the ceiling boards can be easily removed, such a ceiling construction is not provided with the access door. In the ceiling construction erected by the concealed construction method, the ceiling boards are mounted on the main beams by the employment of access angles and hooks in suitable positions on the ceiling whereby the ceiling boards can be removed and thus, as in the case of the ceiling construction erected by the exposed construction method, in the ceiling construction erected by the concealed construction method, the access door is not usually employed. However, when the ceiling boards are designed to be removed, as the ceiling boards are removed and reinstated, the ceiling boards tend to be damaged or smeared leading to undesirable results.
In the ceiling construction erected by the dry wall construction method, since the ceiling boards are not detachable, the access door is disposed in the access opening formed in a suitable position of the ceiling surface. In such a case, taking the weight of the access door into consideration, the access door is attached to the frame channel bound to hanger wires secured to the ceiling slabs by wire fasteners or attached to the frame channel bound to the main beams. In such an access door mounting arrangement, the construction method of the ceiling construction is very troublesome. Especially, when the frame channel is directly hung from the ceiling slabs and the access door is attached to the frame channel, after a prolonged use of the ceiling construction, an undesirable step is formed between the access door and ceiling wall.