On May 19, 2019, the video of "the outer wall of Yuefu new house in the park was lifted by the strong wind" was widely spread on the Internet. Why can't Huilongguan's most expensive commercial house resist the strong wind?

The latest response of the developer Beijing Investment Development Co., Ltd. has removed all decorative panels that are in danger of falling off, and is expected to complete a comprehensive inspection within two days. At the same time, the authoritative testing organization also arrived at the project site and conducted inspection in combination with site conditions, wind conditions and other factors.

The strong wind lifted the outer wall of the residential building

On the afternoon of May 19, the external wall thermal insulation decorative board fell off at the flue on the west side of Building 2 of Yuefu project in Changping Park developed by Beijing Jingtou Yintai Suntech Real Estate Co., Ltd. although it did not hurt pedestrians and vehicles, it smashed the roof of the surrounding buildings. Soon, the video of the wind lifting the outer wall was widely spread on the Internet.

According to the reporter, park Yuefu is the only new house on sale in Huilongguan area, with an average selling price of 58500 yuan / m2. The first phase was just delivered at the end of last year. Why can't such an expensive commercial house resist the strong wind? Many owners who bought Yuefu Park expressed concern one after another and asked to strictly investigate the reasons for the falling off of the decorative board.

Response of the housing and Urban Rural Development Commission: an investigation has been conducted

On the evening of May 19, Beijing Investment Development issued a letter of apology and said that it would arrange the follow-up work of exterior wall restoration one by one, and strive to completely eliminate the hidden dangers in the shortest time under the supervision of authoritative institutions.

On the afternoon of the 20th, the Beijing Municipal Commission of housing and urban rural development also said that the urban two-level Commission of housing and urban rural development attaches great importance to the project and has investigated the project. If it is found that the construction and construction units have violations, it will resolutely and seriously deal with them.

Late at night on the 20th, the reporter got the latest briefing from the development of Beijing investment. It was first mentioned in the notice that after the wind reduced at 4:00 a.m. on May 20, the project construction unit organized "Spider Man" to conduct a comprehensive inspection on the falling parts of the decorative plates on the west side of Building 2, and remove all the decorative plates that are in danger of falling off. As the wind is still strong during the day, considering the safety of construction personnel, we were forced to suspend the extended inspection of all floors of Building 2. After the weather conditions meet the safety work requirements, we will continue to carry out the work, and it is expected to complete the comprehensive inspection within two days.

At the same time, the developer also contacted the authoritative testing organization to arrive at the project site, checked it in combination with the site conditions, wind conditions and other factors, and analyzed the items such as "bonding strength analysis (the term" strength "is provided by the industry Encyclopedia)" and "tensile strength (the term" tensile strength "is provided by the industry Encyclopedia)" according to the site and construction drawings. After sorting and analyzing the data, the testing unit will submit a specific testing report. In addition, relevant experts from the Chinese Academy of Building Sciences will also come to the project site for on-site inspection, professional investigation and scientific experiments within two days.

According to the engineering construction experience, the external wall insulation and decoration integrated board lifted by the strong wind is usually fixed on the wall through connectors. Some people on the Internet speculate that the falling off event may be caused by a gap on the surface of the wall or a hole between the thermal insulation decorative board and the building, but the specific reason has to wait for the test report.

In recent years, no matter the projects under construction or existing buildings, the external walls fall off frequently, and many even cause personal safety accidents. In this context, the quality and installation of exterior walls are particularly important. How to complete a safe and effective external wall insulation project is a very key problem. Then the following Chinese curtain wall network alwindoor Let's explore this problem from why the outer wall falls off. Www. 68mn.

First of all, we don't pay attention to the quality of moisturizing materials, because if the quality of exterior walls is not qualified, then there will be falling off events. The difference is only the time and scale. Therefore, the following analysis and description are only based on the premise that the quality of thermal insulation materials is qualified.

Reasons for exterior wall falling off:

1. Basic structure factors. At the joint between concrete beam column and masonry, the external wall of frame structure is prone to the damage of thermal insulation layer caused by masonry deformation (the entry "deformation" is provided by the industry Encyclopedia). The openings of scaffolds are not compacted, forming a thermal insulation layer, and the local base course is not firm and damaged. The exterior wall decoration components are not firmly fixed and displaced, forming a push-pull effect, which makes the insulation layer hollow locally and water seepage for a long time after cracks, and finally leads to the falling off of the insulation layer;

2. Improper compression measures. The surface load of the insulation board is too large, or the resistance measures to the negative wind pressure (the entry "wind pressure" is provided by the industry Encyclopedia) are unreasonable. For example, the bonding method of non nail bonding is adopted for the outer wall of coastal areas or high-rise buildings, which is very easy to make the insulation board empty and fall off due to the damage of wind pressure;

3. Improper treatment of wall interface. Except for clay brick wall, other walls shall be treated with interface mortar and then coated with slurry insulation material, otherwise it is easy to cause direct hollowing of insulation layer or failure of interface treatment material, forming hollowing of interface layer and main wall, and forming hollowing of insulation layer. The surface of the insulation board also needs to be treated with interface mortar, otherwise it will also cause local hollowing of the insulation layer.

Secondly, let's see what kind of problems will appear on the outer wall. Generally speaking, when the construction is completed for a period of time, or after the cyclic change of temperature in winter and summer, the unqualified exterior wall will be exposed for various reasons. Generally speaking, there will be the following four major problems.

1. The insulation layer falls off. Due to the quality problems of the materials used and the carelessness in the construction process, the external wall insulation board is prone to displacement, hollowing and falling off, and the slurry insulation layer is prone to hollowing and falling off. If it is not handled in time, the thermal insulation effect of the wall will be greatly reduced.

2. The plastering layer is cracked. The external wall thermal insulation plastering layer is composed of plastering mortar and reinforcing mesh. The plastering mortar is divided into bottom mortar and surface mortar. The heat insulation layer can not solve the problems of weather resistance, weather resistance, air resistance, cracking resistance, etc.

Generally, the cracking of plastering layer is due to material factors. The density of thermal insulation board for external wall insulation shall be 18 ~ 22kg / m3. Some construction units will shoddy and adopt thermal insulation board below 18kg / m3. The density is not enough, which is easy to cause cracking of plastering mortar layer; The natural shrinkage time of the insulation board is up to 60 days in the natural environment. If the aging time is less than seven days, the insulation board will be put on the wall. As a result, the insulation board will continue to shrink after being put on the wall, and the plastering mortar layer adhered to the insulation board will be cracked.

When the sun shines directly on the surface of plastering mortar in summer, the surface temperature of plastering mortar (the entry "surface temperature" is provided by the industry Encyclopedia) can reach 50 ~ 70 ℃. In case of sudden rainfall, the temperature of mortar surface will drop to about 15 ℃, and the temperature difference can reach 35 ~ 55 ℃. This change in temperature difference and the influence of day night temperature difference and seasonal temperature lead to large difference in deformation of plastering mortar layer, which is easy to produce cracks.

3. Indoor condensation. Because there are too many decorative lines singled out with concrete in the inner wall, and the proportional relationship of concrete pouring (the term "pouring" is provided by the industry Encyclopedia) has been determined during thermal insulation, the thermal insulation treatment of this part has been abandoned. These exposed concrete parts without thermal insulation treatment will cause frost return and condensation in the room, which is easy to lead to moisture and mildew on the wall.

4. The external wall tiles are hollowed out and fall off. The variation of temperature difference in different seasons and day and night makes the facing brick subject to the influence of three-dimensional temperature stress. The local stress of the facing layer will be concentrated in the vertical and horizontal walls or the junction between the roof and the wall. If it is in the middle of a large area of the wall or the local extrusion of adjacent facing bricks, it will cause the face brick to fall off.

Due to the deformation and hollowing of the plastering mortar layer, the face bricks fall off in a large area. Because the materials of each layer of the composite wall are incompatible and the deformation is uncoordinated, the face brick is displaced. The waterproof measures of the exterior wall are not in place. It will lead to water infiltration, repeated freezing and thawing cycles, damage the bonding layer of the face brick and cause the face brick to fall off.

Finally, as for how to avoid problems of exterior wall, in addition to using qualified materials, we should deeply understand and seriously implement the code for construction and acceptance of exterior wall facing brick engineering. At the same time, it should also be noted that the code puts forward several noteworthy problems in the basic provisions of design:

1. Shrinkage deformation caused by temperature change during use is often one of the main factors causing bulging and falling off of exterior wall facing bricks.

2. Setting expansion joints can prevent cracking and falling off caused by the deformation of wall structure and the temperature deformation of exterior wall facing brick itself.

3. Caulking with flexible waterproof materials can absorb deformation and increase the impermeability of the finish.

4. If the joint of facing brick is too small, it is easy to fall off under the action of temperature stress. The specification is "the width shall not be less than 5mm". The code also emphasizes that the bond strength of facing bricks should be inspected according to the standard for bond strength inspection of facing bricks in construction engineering.