Our province has issued new regulations-
The speed of building houses has slowed down, building a floor for at least 7 days
It will be implemented from February 1st to avoid housing quality problems caused by excessive construction speed
Prefabricated buildings will become the mainstream mode of residential construction in Hangzhou
Our reporter Li Yiheng and Xu Shujing/Text
In the past two years, the term "high turnover" was once very popular in the property market.
In order to improve the efficiency of cash use, reduce costs, and quickly scale up, some real estate companies that are known for their high turnover can produce plans on the day they acquire the land, open the market within three to four months, and return the funds in five months. Monthly cash flow returned to positive.
Such a high turnover will inevitably affect the construction period. In order to catch up with the construction, some real estates are built so fast that they can build a house in 5 days or even 3 days. Cause great project quality and construction safety hazards.
In response, the Zhejiang Provincial Department of Housing and Urban-Rural Development issued the "Implementation Opinions of the Zhejiang Provincial Department of Housing and Urban-Rural Development on Implementing the Primary Responsibilities of the Construction Unit’s Project Quality" (hereinafter referred to as the "Opinions"), which clearly stipulates that "the reduction of the construction period exceeds the quota by 30 % Or more and the construction period of the cast-in-place concrete main structure is less than 7 days per floor. Increase the frequency and intensity of inspections of the corresponding construction projects.” This also means that the construction period of the cast-in-place concrete main structure shall not be less than the standard requirements. It should not be less than 7 days/layer.
The "Opinions" came into effect on February 1 this year.
Cast-in-place concrete main structure
The construction period should not be less than 7 days/floor
The Qianjiang Evening News·Hours reporter learned from the Provincial Department of Construction that the reason for the promulgation of the “construction period of the cast-in-place concrete main structure should not be less than 7 days/floor” is to strictly implement the national standards to ensure the quality of construction projects.
The first paragraph of Article 6.7.5 of the National "Concrete Quality Control Standard" (GB50164-2011) stipulates: "For the concrete configured with Portland cement, ordinary Portland cement or slag Portland cement, watering and dampness shall be used. The maintenance time covered shall not be less than 7 days".
The relevant person in charge of the Provincial Department of Construction said that previously, in the process of commercial housing development, some real estate development companies, for the purpose of "fast development and fast sales", existed in the phenomenon of shortening the development cycle and reducing project costs.
"Real estate companies are keen on arranging the construction period according to the minimum period, which is prone to common quality problems."
In fact, as a traditional house construction method, cast-in-place concrete has a specific construction period.
An industry insider who has been engaged in the construction engineering industry for many years said that the underground excavation and piling and basement phases of common high-rise residential buildings on the market take the longest time. After entering the main structure construction phase on the ground, the speed will be much faster. Generally speaking , The first and top floors are a little time-consuming, while the middle standard floor usually takes a week to build each floor.
"The cast-in-place concrete construction process of each floor includes woodwork support formwork, reinforcement work arrangement steel bars, electrical wiring pipes, etc., and needs to go through procedures such as acceptance of the reinforcement formwork, pouring preparation, formal pouring, and maintenance before starting the next floor. Construction, the whole process will take about 7 days, which is still in the case of a high level of construction."
What are the consequences if the construction period is less than 7 days/layer?
The industry insider said: “Cement mortar and concrete need time to solidify and dry out to reach safe strength. If the construction period is too short and the structural strength does not meet the standard, continuing construction and capping on such a floor will cause the beams, Deformation of the column can easily cause collapse.” Even if the situation is not as serious as the collapse, it will easily lead to problems such as cracks in the concrete, water leakage, block dropping, mold explosion, and appearance defects in the later stage, thereby shortening the service life of the building.
Another construction engineering expert also said: “Some developers in South China only need 5 days/floor to construct the standard floor. However, South China is close to the tropics and the climatic conditions are different from Zhejiang. When South China developers come to Zhejiang for development, the standards of South China are not applicable. The construction period should not be less than 7 days/floor."
Residential buildings in the main urban area of Hangzhou
Prefabricated buildings have become mainstream
A few years ago, a 57-story skyscraper in Changsha, Hunan Province was built in just 19 days. The "speed of China" shocked the world, and netizens lamented that China's "infrastructure madman" is well-deserved.
In fact, this skyscraper in Changsha is constructed using a prefabricated construction method.
Prefabricated construction refers to the transfer of a large number of on-site operations in the traditional construction method to the factory, where the building components and accessories, such as floor slabs, wall panels, stairs, balconies, etc., are processed in the factory, and transported to the construction site through reliable The connection method is assembled and installed on the spot. For an image, building a house is like "building blocks."
Compared with traditional cast-in-place concrete construction methods, prefabricated construction is less affected by weather and environmental factors, reducing on-site construction time and labor costs, reducing construction waste, and greatly reducing hollowing, tilting, and external wall leakage. The occurrence of the occurrence of steel structure, especially the steel structure, the housing acquisition rate can be increased by 4%-8%.
In 2017, Hangzhou became the first batch of "National Prefabricated Building Demonstration Cities" in the country, and issued implementation opinions on promoting the development of green buildings and building industrialization.
In September of that year, the first new-type construction industrialized affordable housing project in Zhejiang Province, Deze Homes, Jingshifang Community, located in Sandun North, Hangzhou, was delivered by prefabricated construction.
In recent years, Hangzhou has continuously increased the proportion of prefabricated buildings in newly built buildings. Since 2017, the residential land in the main urban area of Hangzhou has basically required 100% implementation of prefabricated buildings. Residential projects in urban areas are mostly prefabricated buildings.
In July 2019, Fuyang District also issued a policy to clarify that 100% of the newly sold commercial residential land will be prefabricated construction from the date of release.
The requirements for prefabricated buildings in various projects are usually indicated in the "Construction Conditions Guidelines" when the land is listed.
For example, in the third batch of centralized land supply in Hangzhou at the end of last year, with the exception of the two plots of Xiaoshan Shushan Unit and Shushan West Unit, other plots clearly required in the transfer announcement to "implement all prefabricated construction in accordance with the requirements of building industrialization."
The project manager of a leading developer in Hangzhou said: "At present, Hangzhou has requirements for the proportion of prefabricated buildings. Cast-in-place concrete technology is mainly used for basement and pile foundation projects. The main body of the building uses cast-in-place concrete projects much less than before. "
So, how long does it take to build a floor under prefabricated construction?
A construction engineer from a real estate company said: "According to the actual operation of the past two years, the construction period of the standard floor of the main structure is about 10~11 days/floor, 7~8 Sky/layer, mainly installation, splicing and maintaining flatness are more labor-intensive and time-consuming. However, the biggest advantage of prefabricated construction is that it is green and environmentally friendly, and its safety and quality are relatively more reliable."
In September last year, Hangzhou's first prefabricated integral steel structure residential district "Rongxin Aoshi Mansion" project started construction.
Compared with prefabricated concrete structures, prefabricated steel structures have more advantages. First, the building structure has good adaptability and excellent seismic performance; second, the degree of standardization is higher; third, the assembly rate is high, which is the future development direction of green buildings.
The Hangzhou Municipal Construction Commission announced last year that during the "13th Five-Year Plan" period, the proportion of newly started prefabricated buildings in Hangzhou increased to 31%.
In addition, it is planned to steadily promote the green energy-saving renovation of existing residential buildings during the "14th Five-Year Plan" period, and strive to achieve 35% of the prefabricated building area of newly built urban buildings that year.