The performance of waterproofing of the external walls of buildings is the key to ensure the long-term focus of the building. With the acceleration of urbanization, the number of high-rise buildings is increasing, and the problem of water seepage on external walls has become more prominent. In this paper, we will discuss the main reasons that lead to the failure of waterproof mortar and water seepage on the external walls of buildings, and how to prevent these problems through scientific and reasonable construction and maintenance.
Water seepage problem of building exterior wall
Water seepage refers to the penetration of water into the interior through the building exterior wall, resulting in wet marks, mold and other problems on the wall. This phenomenon not only affects the aesthetics and service life of the building, but may also have an adverse effect on the indoor environment and threaten the health of the occupants. Next, we can analyze water seepage on the exterior walls of buildings from the following reasons.
The main causes of water seepage on external walls of buildings
Improper construction operation
Improper construction operation is one of the main causes of water seepage on external walls. The construction of waterproof mortar needs to be operated in strict accordance with the specifications, but in the actual construction, often in order to catch up with the schedule, the construction unit will simplify the steps, and even ignore some important operational points.
Layered plastering is not in accordance with the regulations
In accordance with the waterproofing requirements, the external wall plastering should be divided into five times, each layer of plastering needs to be fully dry before the next layer. However, in order to save time and manpower, some construction units adopt one-time plastering method, resulting in uneven thickness of mortar layer and easy to appear cracks.
Improper treatment of grass-roots level
Subgrade treatment is an important part of ensuring waterproof effect. If the external frame pipe holes are not plugged well, the dust and dirt on the surface of the wall is not cleaned up, or water is not sprinkled and moistened in advance, it will lead to a weakening of the bond between the mortar and the wall, which will ultimately result in hollow drums and cracks.
Inaccurate mortar ratio
The mixing ratio of waterproof mortar needs to be adjusted according to the specific conditions of the building. If the mortar specification is too large, although it increases the strength, it will also lead to excessive mortar shrinkage and cracks, thus affecting the waterproof effect.
Problems with the plain gray layer
After the cement mortar is calendered, it is a common practice to brush a layer of plain gray on the outside. However, due to the different degree of contraction between the plain ash and the cement mortar, it is easy to lead to dry cracks in the plain ash layer, which further affects the waterproof performance of the external wall.
Poor maintenance after construction
Post-construction maintenance is also an important factor affecting the waterproofing effect. If the maintenance is not appropriate, especially in the case of large temperature difference or wind drying, the plaster surface layer is prone to produce shrinkage cracks, the formation of tortoise cracks, and ultimately lead to water seepage.
Detailed analysis of improper construction operation
Comparison between one-time plastering and layered plastering
Although layered plastering is time-consuming, it can ensure the uniformity of each layer of plaster and sufficient drying time, effectively reducing the generation of cracks. Although one-time plastering saves time, it is easy to cause the mortar layer to be too thick, and the internal drying is not sufficient, resulting in the phenomenon of air cracks.
The relationship between the thickness of plaster layer and waterproof effect
The thickness of the plaster layer directly affects the waterproof effect. If the thickness is too large, it is easy to produce shrinkage cracks; if the thickness is too thin, the waterproof effect is not ideal. Therefore, the thickness of the plaster layer should be strictly controlled during construction to ensure that the waterproofing effect can be achieved and cracks are not easy to appear.
Impact of improper treatment of the base layer
Importance of wall surface treatment
The quality of wall surface treatment directly affects the adhesion of waterproof mortar. If the surface is not sufficiently cleaned or not wetted in place, the mortar will not be able to firmly bond with the wall, which is prone to cavitation and cracks.
How to correctly treat the grass-roots level
Proper treatment of the substrate includes plugging holes, cleaning the surface of dust and dirt, and sprinkling water to moisten the substrate before construction. This can improve the adhesion between mortar and base and reduce the occurrence of air cracks.
The relationship between the wetness of the base and the adhesion of mortar
The wetness of the grass-roots level is a key factor affecting the adhesion of mortar. If the substrate is too dry, the moisture in the mortar will be rapidly absorbed, resulting in a reduction in the strength of the mortar and easy cracking.
Consequences of inaccurate mortar mix ratio
Effects caused by too large mortar marking
Although the mortar marking is too large can increase the strength, it is also easy to cause shrinkage cracks and affect the waterproof effect. Therefore, the mixing ratio of mortar should be scientifically adjusted according to the actual demand, avoiding the blind pursuit of high strength.
The scientific method of mortar ratio determination
The determination of the mortar proportion should take into account the structural characteristics of the building, climatic conditions and the use of the environment, to ensure that it can meet the waterproofing requirements, but will not produce cracks due to excessive shrinkage.
Shrinkage difference between the plain ash layer and cement mortar
Causes of shrinkage cracks
The difference in shrinkage properties between the lime and cement mortar can easily lead to cracks in the surface layer. Such cracks not only affect the aesthetics, but also reduce the waterproof performance of the external wall.
How to avoid dry cracks in the plaster layer
In order to avoid dry cracking of the plaster layer, you can adjust the proportion of the plaster, increase the use of flexible materials, or use different construction techniques to reduce the difference in shrinkage.
Hazards of poor post-construction maintenance
Influence of temperature difference on plastered surface layer
Temperature difference will cause thermal expansion and cold contraction of the plastering layer, resulting in cracks. Especially in areas with large temperature difference between day and night, the maintenance after construction is especially important.
Cracks caused by improper maintenance
If the maintenance is not proper, such as in high temperature or windy weather without taking protective measures, the plaster surface layer is prone to cracks, thus affecting the waterproof effect of the external wall.