The quality level of construction projects has improved to a certain extent, and social complaints about the quality of housing have also increased. Leakage in external walls accounts for a certain proportion, but it has caused harm to the normal life and use of residents. A huge inconvenience. Based on several years of experience in house quality maintenance, the author talks about his understanding and practical experience in this regard.
1. Analysis of the causes of wall leakage:
1. The filling walls in current frame structure residential projects are basically non-load-bearing lime sand bricks or small blocks. Lime sand bricks and small blocks are prone to defects such as breakage, missing edges and corners during transportation and construction. If the existing exterior wall is damaged during construction or is drilled due to the need for concealed installation of equipment pipes, the exterior wall masonry will be artificially damaged and water seepage will easily form in the exterior wall masonry.
2. Workers did not strictly follow the construction specifications during masonry construction, and the masonry mortar was not full, especially the vertical joint mortar. In addition, if the strength of the mortar is not up to standard or dry bricks are installed on the wall, the water in the mortar will be absorbed by the bricks, resulting in low strength of the mortar, causing the bricks and mortar to separate, and the overall stiffness of the masonry will decrease, resulting in cracks in the wall.
3. Temperature differences cause cracks at the junction between concrete structural beams and columns and infill walls.
4. The one-time primer for the exterior wall plaster layer is too thick or the partial primer is too thick to ensure the full height verticality, and appropriate strengthening measures are not taken, resulting in cracks; the surface of the wall layer is too smooth , poor bonding; a large area of ??the exterior wall was laid with no dividing lines on the base layer, resulting in irregular shrinkage cracks.
5. The facing bricks are hollow or the mortar is not full, and the gap between the facing bricks and the mortar can easily form a water storage container; the joints of the facing bricks are not dense or the joints are cracked, and the tight joints and joints are missing. All of them allow rainwater to seep in from the surface, causing water accumulation and causing leakage. In addition, the easy water seepage of the wall is also related to the joints of the tiles and the uneven surface of the tiles. The concave joints make the overall wall surface of the exterior wall not smooth, the flow rate of rainwater slows down, and the water retention time and amount increase, especially at the lower edge of the joints. The quality of the joints is not up to standard or long-term exposure to wind and rain causes micro cracks between the joints and the tiles, causing leakage.
6. During the construction of the surface of horizontal components such as window sills, sun visors and awnings, the slope is not found or even reversed, causing backflow or accumulation of water, and it is also easy to cause water seepage on the exterior wall.
2. Measures to prevent and control external wall leakage:
1. In order to improve the waterproofing ability of the bricks used in the construction of external walls, the bricks facing the outside should be selected with complete edges and corners. , and bricks must not be laid during the masonry process. When the length of the wall does not match the brick modulus, the part lacking the modulus shall be adjusted by solid bricks or plain concrete. After the exterior wall masonry is built, you should try to avoid chiseling. If there are pre-buried hidden pipes, you can leave open joints on both sides of the pipe installation location in advance, and tie steel bars every 600mm vertically between the joints. The tie bars extend 250mm into the wall, and C20 fine stone concrete is poured after the construction. At the same time, wall defects such as scaffolding eyes, cable holes, etc. must be repaired first before painting, so as not to leave any hidden dangers.
2. Construction technicians should conduct technical briefings on workers and strengthen spot checks. It is strictly forbidden to put dry bricks on the wall. Strictly control the mortar mix ratio to ensure the fullness of the mortar. The horizontal joints must be fully covered with mortar. Use a hook trowel to carefully refill the mortar and hook and fill to ensure the quality of the outer vertical joints. The upper and lower mortar joints of the sloped roof should be checked again on the external wall operating frame 3 days before plastering. If there are any cracks that are not hooked and have sunken, they should be filled in. The sunken cracks should be kicked out with a width of not less than 10mm. Seam to ensure that the hook is filled tightly.
3. For cracks caused by temperature differences, the cracked base layer should first be chiseled away, steel mesh should be added, and then high-grade cement mortar should be used to layer the cracks and pay attention to maintenance, and then surface. Layer construction can effectively prevent the occurrence of cracks and achieve the purpose of reducing wall leakage. If phenomena such as splayed cracks under the top window and vertical cracks under the window occur, the method of adding long reinforced concrete to the top window sill to cap the window panel can be used to enhance the stiffness and eliminate cracks.
4. For cracks in the base layer, first of all, it is necessary to ensure that the exterior wall primer is not too thick, and steel wire mesh should be used to strengthen the local areas that are too thick. Secondly, the exterior wall primer should be divided into layers and layered. The bottom should be protected from exposure to the sun or rain before final setting, and maintenance should be strengthened. Make good grid lines, especially for exterior walls such as bricks and mosaics where the decorative surface layer has no grid lines. The grid lines should also be left in appropriate locations, and the cracks can be filled with grease before the top layer can be applied. Third, for smooth structural layers such as concrete columns and beams, use polymer mortar to "texture" them (the polymer mortar mix ratio can be 107 glue:water:cement:sand=1:4:10:10. Measure and stir evenly. ), apply it on a smooth surface and wet-cure it for 7 days to "texture" it to enhance the adhesion, and then apply a full primer to avoid defects such as hollowing and poor bonding.
5. For buildings with exterior walls paved with tiles, technical explanations must be made in advance before exterior wall construction. During the paving process, there must be a squeezing process, and the hollowing situation must be comprehensively checked before the jointing. The jointing must be dense. After the jointing is completed, attention must be paid to moisture maintenance. The sealing seams must not be missed. The depth of the jointing must be It is recommended to strictly control, the concavity should not be too large, and it is best to make an arc-shaped flat seam. In terms of quality management, a multi-level review control system should be established to ensure the quality of each process.
6. Horizontal components such as window sills, sun visors, awnings, etc. should be sloped as required and in the correct direction. The parts in contact with the wall should be treated with flooding arc corners to prevent reverse flooding. Or standing water.
The periphery of the window frame should be raised and glued, the plug behind the window should be tightly sealed, and a drip line trough must be made above the window opening (both the depth and width should not be less than 10mm). During roof construction, special attention should be paid to the fact that the concrete at the root of the parapet wall should be poured 10-15mm more than the concrete on the roof to ensure that the construction joints at the root of the parapet wall are higher than the roof panels. Cracks will not cause water seepage at the base of the parapet wall, ensuring a beautiful appearance of the building.
7. Two new materials can be used to prevent external wall leakage: ① Add Dura fiber to the cement mortar for exterior wall plastering; ② Use waterproof and anti-leakage colored caulking materials for exterior wall bricks Caulk.
Compared with plastering cement mortar without Dura fiber, its crack resistance is improved by 80%