Exterior wall coating finish how can crack? How to avoid this hole?

Shortly after the many buildings built, exterior wall coating finish will craze, serious impact on the structure of the beautiful; In addition, the crack caused by the metope of ooze water not only influence the use function of the building, also affect the structure of the building safety, engineering quality hidden trouble. So, what is the cause of the exterior wall paint cracking? What's the preventive measures? The causes of cracking of exterior wall coating facing 1. Cracking at the grass-roots level of exterior wall coating facing for cement mortar plastering layer at the grassroots level in the condensation process can produce dry shrinkage and temperature shrinkage. Outer wall plastering construction undeserved, can cause the empty drum and cracking. In front of the coating surface construction, do not pay attention to repair, then move to the next working procedure. After a period of sunshine and wipe, internal cracks will gradually outward development. However, has a very thin film coating surface layer is difficult to resist stress, and accordingly the craze. 2. Exterior wall putty putty layer cracking defects lead to poor crack resistance; Or due to improper operation, be bored with child after scraping metope due to drying shrinkage, cracking, which influence the coating surface. 3. Coating surface cracking due to poor crack resistance or improper construction, some quality problems of coating after weathering prone to drying shrinkage cracking and other quality problems. 1 construction of exterior wall coating facing cracking preventive measures. Exterior wall mortar surface ( 1) Use outer wall plastering cement mortar should be properly selected, the proportion of 1:2. 5 mortar generally right, try not to use 1:1 or 1:2 cement mortar. Cement dosage is overmuch, mortar contraction, prone to fracture. ( 2) In strict accordance with the outer wall plastering construction operation procedures and process, must be carefully before rendering clear at the grass-roots level surface dust, dirt, grease and ear gray brick wall, etc. The day before construction, wall must be wetted by water. 24 hours after completion of construction of the wall must be water conservation. Every day watering frequency is determined according to the climatic conditions, and at least two times a day, curing time shall not be less than 7 days. ( 3) If in the sunny season construction, scientific arrangement of construction time, construction, avoid sun exposure or take effective measures, the shade guarantee dry mortar surface shade, prevent the sun drying shrinkage too fast causing cracking plaster mortar layer. ( 4) Cement mortar plaster surface framework should not be too big, make full use of granite to can adjust the shrinkage of cement mortar bolt. Construction, the use of triangular or trapezoidal cross-section lath separation of cement mortar. Construction joints is not permitted in the same construction. Joint sealant should be applied on a separate joint. 2. Exterior wall putty layer construction ( 1) Exterior wall putty layer construction should be in plaster to start after the curing period. ( 2) Before the group of scraping putty, should check plaster mortar layer, the part of the cracks to appear empty drum, in advance 2 ~ 3 d be repaired. Remove dust and sand floating on the surface of the plaster, keep the plaster surface clean. ( 3) Construction shall be in strict accordance with the specifications and requirements of the product specification, to ensure that the putty layer with plaster bonding is firm, no crack. At the same time, in the process of construction must avoid sun exposure, and ensure the putty layer in a cool and dry condition. ( 4) After completion of the polishing putty layer should be timely maintenance, polishing powder produced should rinse metope at the same time, in order to enter the coating surface. 3. Coating surface, 1) Before the paint surface, putty layer should level off, firm, clean, no looseness, pulverization, defects such as peeling. Shall promptly repair any defects found during the inspection. ( 2) According to the paint finishes construction specification and coating product requirements, coating surface can only be in damp environment