1 phenomenon
(1) The connection is obvious.
(2) Cracks appear on the ceiling surface, especially at the joint.
(3) The surface layer has large deflection, unevenness and even deformation.
2. Cause analysis
(1) If the connection is obvious:
1) The derrick is unevenly spliced with the keel (joist) and the main keel is unevenly spliced with the secondary keel.
2) The ceiling panel splicing is uneven, or the adhesive tape paper (cloth) pasted at the splicing place is not processed, and the batch of putty is not leveled, which leads to the obvious protrusion of the splicing place and the formation of joints.
(2) Surface cracks:
1) The wood material is poor, with high moisture content and large shrinkage and warping deformation; Using light steel keel or aluminum alloy ceiling, the vertical and horizontal lines of suspender and primary and secondary keel are not straight, and the connection is not tight, which will be displaced and deformed after being stressed.
2) The water content of the ceiling panel is too high, or the product is not completely stable for a short time, which leads to the shrinkage and deformation of the panel (especially the PC board and other products).
3) The whole joint is tight, flat-topped, and the flat-fell seam is improperly handled or not in place, which is easy to produce cracks at the flat-fell seam.
(3) The deflection of the surface layer is large and uneven;
1) See Article 1) of Cause Analysis (II) in this paper.
2) The suspended ceiling construction is not operated according to the regulations (specifications), and a horizontal line pops up on the surrounding wall according to the baseline in advance, or the suspended ceiling is not arched according to the specifications.
3. Preventive and control measures
(1) If the connection is obvious:
1) The connection between the boom and the main keel, the main keel and the secondary keel shall be smooth.
2) The splicing of ceiling panels should be smooth. If there is no structural interface at the edge of the panel at the joint, it should be planed off about 2mm in advance, so that the interface will be flush with the bedding face after the adhesive tape paper (cloth) is pasted at the joint.
3) Batch of putty should be smooth, flat-fell seam should be carefully scraped to be dense and smooth. The sand skin must be put in place, and it can be nailed to the wooden crab and polished evenly to ensure its smoothness and eliminate seams.
(2) Surface cracks:
1) The derrick and keel are installed smoothly, and the stress nodes are tightly combined. Try hoisting with heavy objects such as sandbags so that the panel can be installed without displacement or deformation after being stressed.
2) Gypsum board with high water absorption rate should not be used as the panel of high humidity space; Materials such as FC board should be relatively stable after shrinking before use.
3) When gypsum board is used, the distance between the self-propelled screw and the edge or end of the board should not be less than 10mm or greater than16mm; ; The spacing of screws in the plate should not be greater than 200mm.
4) The flat-fell seam of the whole flat roof should be evenly left with a seam of about 2mm. Elastic putty should be embedded, or 107 glue or woodworking white glue mixed with white cement can be mixed with appropriate gypsum powder as flat-fell seam putty until it is dense, and 1 ~ 2 layers of Rachel tape paper or cloth should be pasted outside. The knotting belt should be embedded with dacron cloth or woven mesh belt, and then it should be flat-topped, as shown in Figure 6.
Figure 6- 1 Joint Treatment of Ceiling Plate
(3) The deflection of the surface layer is large and uneven;
1) See Article 1) for prevention and control measures (Article 2).
2) Suspended ceiling construction shall be operated according to regulations, and the reference line shall prevail in advance, and horizontal lines shall pop up on the surrounding walls; At the same time, in the process of installing the ceiling, it should be horizontal, flat and vertical, closely connected, and arch camber should be carried out according to the specifications.
2) Quality defects of the framed ceiling
1 phenomenon
(1) Uneven frame joints and uneven vertical and horizontal lines.
(2) The upper frame plate is deformed in a pot bottom shape, and the wooden splint plate has nail marks.
(3) The bottom surface is uneven and the middle part falls off.
2. Cause analysis
(1) Uneven frame joints and uneven vertical and horizontal lines;
1) Before installing the ceiling, it was not planned according to the ceiling plane, and it was divided into blocks reasonably and accurately.
2) When installing the ceiling, there are no vertical and horizontal cables and elastic lines; When assembling nail plate, flat-fell seam, frame and square were not strictly according to the datum line.
(2) The frame plate on the pot bottom is deformed, and there are nail marks on the wooden splint;
1) The material of the frame plate does not meet the requirements and the deformation is large.
2) Improper material selection of frame plate, gypsum board and other plates with high water absorption rate should not be used in basement or high humidity environment, which is easy to deform.
3) The frame plate is not firmly bound or the frame area is too large; The method of nailing nails with splint is incorrect, the depth is not enough, and the nail tail is not embedded with putty.
(3) The tension of steel hanger is inconsistent.
3. Preventive and control measures
(1) Uneven frame joints and uneven vertical and horizontal lines;
1) Before the ceiling is installed, it should be planned in a unified way according to the plane size of the ceiling, and it should be divided into blocks reasonably and accurately.
2) When installing the ceiling, vertical and horizontal stay wires and elastic wires must be used; When assembling the nail plate, flat-fell seam, frame and square wood should be made in strict accordance with the baseline. The vertical line is based on the left line, and the horizontal line is based on the upper line.
3) The ceiling board must be uniform in size, square and straight and smooth around.
(2) The frame plate on the pot bottom is deformed, and there are nail marks on the splint;
1) The material of the frame plate should meet the quality requirements, and the material with small deformation is preferred.
2) The frame board must adapt to the environment, such as the basement or the environment with high humidity and the heavy rain outside the hall. Plasterboard and other boards with high water absorption should not be used.
3) The binding of the frame plate must be firm, or the frame area shall be determined according to the rigidity and strength of the plate.
4) the glue structure is suitable for fixing the splint (a small number of nails can be used in combination); When metal nails (headless nails) are used, the depth of nailing into the splint should be greater than 1mm and embedded with putty, and nail marks should not be exposed.
(3) Before installing the grid plate, use adjustable steel hanger, spirit level and reserve arching.
3) Quality defects of gusset ceiling
1 phenomenon
(1) Flat-fell seam and gusset seam are obvious.
(2) The deformation or deflection of the board surface is large, and the gusset plate falls off.
2. Cause analysis
(1) Flat-fell seam and gusset seam are obvious:
1) The plate cutting opening is not square, neat and complete.
2) Aluminum alloy and other plates are deformed at the interface during shipment, not corrected during installation, and the interface is not tight.
3) The colors of the gusset plates are inconsistent.
(2) The plate surface is deformed or deviated, and the gusset plate falls off:
1) The material of gusset plate does not meet the quality requirements, especially the thin gusset plate such as aluminum alloy is not well kept or is easy to deform and fall off when installed in strong wind, so it can't be corrected generally.
2) The lap length of gusset plate is not enough, or the lap structure requirements of gusset plate are unreasonable and the fixation is not firm.
3. Preventive and control measures
(1) Flat-fell seam and gusset seam are obvious:
1) The plate cutting opening must be square, neat and smooth.
2) If there is any deformation at the interface of gusset plate such as aluminum alloy, it should be corrected during installation, and the interface should be tight.
3) The colors of gusset plates shall be consistent, the splicing and seams shall be smooth, and the splicing shall be in place.
(2) The board surface is deformed and the gusset plate falls off:
1) The gusset plate material shall meet the quality requirements and be properly kept to prevent deformation; Thin gusset plates such as aluminum alloy should not be made outdoors and at the bottom of awning, otherwise they will easily deform and fall off.
2) The joint of gusset plate should keep a certain lap length, generally not less than 30mm, and the connection should be firm.
3) Generally, the span of gusset ceiling should not be too large, and it should be reasonably determined according to the stiffness and strength of gusset plate, otherwise it is easy to deform and fall off.