Calculation formula: floor area ratio = total construction area ÷ total land area.
When the building height is more than 8 meters, the floor area of this floor will be doubled when calculating the floor area ratio.
The lower the floor area ratio, the higher the comfort of residents, and vice versa.
The so-called "floor area ratio" refers to the ratio of the total construction area of a community to the land area. For developers, the plot ratio determines the proportion of land cost in housing, while for residents, the plot ratio is directly related to the comfort of living. So is the greening rate. The greening rate is high, the floor area ratio is low, and the building density is generally low. The less area developers can use to recover funds, the more comfortable residents will be. These two proportions determine whether the project designs the community from the perspective of people's living needs or from the perspective of pure money making. In a good residential area, the plot ratio of high-rise residential buildings is not more than 5, that of multi-storey residential buildings is not more than 3, and the greening rate is not less than 30%. However, due to the limitation of land cost, not all projects can be done.
On plot ratio
Content: the calculation method module of project floor area ratio and profit.
First, the best floor area ratio
The optimal floor area ratio is the floor area ratio value that can maximize profits.
Under certain cost conditions such as land transfer and Jian 'an, the profit of the project depends on the unit price of products and the total amount of products, that is, the total area. The plot ratio determines the total area and unit price. However, with the increase of the plot ratio of the project, the selling price does not decrease proportionally (the selling price of a townhouse project with plot ratio of 1 cannot reach three times that of a high-rise residential building with plot ratio of 3), so the total profit will increase with the increase of plot ratio. When the floor area ratio is higher than the optimal floor area ratio, the product quality begins to decline, the selling price drops, and the profit drops. At the optimal plot ratio point, the difference between sales and total cost is the largest, that is, the profit is the largest. (The black area in the figure is the plot ratio range with positive profit, and the widest point is the point with maximum profit, that is, the optimal plot ratio point. The correlation curve between sales volume and floor area ratio is as follows:
3. Determination of the best floor area ratio
The importance of floor area ratio is clarified, and then the core question is: What is the best floor area ratio of a low-rise project?
To answer this question, it is necessary to carry out economic calculation, that is, under a certain floor area ratio, how much sales area the project can have (the total scale MINUS some necessary supporting facilities) and at what price these areas can be sold. Of course, this price is acceptable in the market and the response is very good. We know that after the plot ratio is determined, the total area and saleable area of the project can be calculated soon, but how to determine the reasonable selling price in the project location. When the cost and other conditions are determined, the price has a great relationship with the comfort of the house. In addition to architectural design factors, the degree of crowding between houses and the number of floors are a very important factor, and these factors are directly related to the floor area ratio. Then the final solution is to establish a "function" between the floor area ratio, the degree of congestion and the number of floors. Of course, this "function" is not a strict mathematical formula, but a correlation analysis.
The following is the basic idea of this correlation analysis. We can roughly estimate the floor area ratio of low-rise or multi-storey residential projects through the number of floors, width and depth of buildings. The methods are as follows:
Suppose the houses in a residential area are evenly distributed, and the following picture is part of it. The four dark gray areas in the picture are houses, and the light gray areas are the base areas corresponding to the average last house. The ratio of the building area of this house to the area of this light gray area can be regarded as the plot ratio of this project.
The residential height is 3m, the depth 12m, the sunshine spacing 1.7 and the number of floors n. The formula for calculating the plot ratio is:
Floor area ratio =( 12 * a * n)/(b * d)- formula 1.
Where d = 3 * n * 1.7+ 12- formula 2.
X = A/B- formula 3.
Substituting Formula 2 and Formula 3 into Formula 1, it can be concluded that the relationship between plot ratio and X and N is as follows:
Floor area ratio =X*N/(0.42N+ 1)
N and x are important values that determine the degree of residential congestion. N is the number of floors in a building, and the residential grade with more floors is correspondingly reduced. X is the ratio of building width to building spacing. The greater the x value, the more inclined the building form is to townhouses. On the contrary, the smaller the x value, the more inclined the architectural form is to be single-family. For example, according to experience, when the value of x is 0.5, that is, the distance between two buildings is close to the width of the building. The architectural forms are basically single-family villas. According to Equation 3, the following table can be made. When determining the floor area ratio, we can easily find that the building is roughly a form, townhouse, Bie Ye, Bie Ye, or some compromise between them.
In the practical application of this method, there are still some problems, mainly because the actual low-rise residential projects are not in a unified ideal state as mentioned above. For example, there are a large area of roads and greening and a large area of supporting public buildings in the project land, so the estimation needs to increase a large correction value; Similarly, if there are many residential types in the land, including townhouses and multi-storey apartments (which is the actual situation of many projects), it is necessary to estimate them separately among different types; If the sunshine interval is not calculated strictly according to 1.7, or there is a large area of east-west residence in the project, the estimation will also encounter some difficulties. But basically, this method needs to be further improved and verified by empirical values. In fact, we can use several existing examples to deduce the result of this formula, get an empirical correction value, and apply this empirical correction value in future calculations.
After obtaining the form of building products with a certain floor area ratio, the corresponding selling price of the product can be obtained according to its crowding degree, the graphic relationship between buildings and the comparison with surrounding projects. At this time, the basic data such as construction area, unilateral cost, total cost and selling price are calculated comprehensively. All finished, the remaining work is to get the final return on capital and net profit of the project through a series of complicated calculations, and see if the project wins or loses under the above product positioning conditions.
X value10.90.80.70.60.50.40.30.2
Building number n
1 0.704225 0.633803 0.56338 0.492958 0.422535 0.352 1 13 0.28 169 0.2 1 1268 0. 140845
2 1.086957 0.97826 1 0.869565 0.76087 0.652 174 0.543478 0.434783 0.326087 0.2 1739 1
3 1.333333 1.2 1.066667 0.933333 0.8 0.666667 0.533333 0.4 0.266667
4 1.492537 1.343284 1. 19403 1.044776 0.895522 0.746269 0.5970 15 0.44776 1 0.298507
5 1.6 12903 1.45 16 13 1.290323 1. 129032 0.967742 0.806452 0.645 16 1 0.48387 1 0.32258 1
6 1.724 138 1.55 1724 1.3793 1 1.206897 1.034483 0.862069 0.689655 0.5 1724 1 0.344828
4. Example project analysis
Entrusted by the developer, our company undertook an investment consultant project in Cheng Nan. Considering the location, cost and other factors, the project product is positioned as a low-rise and low-density residence. The work of determining the project floor area ratio is always the premise and core of all work.
We have identified four possible product types, including single-family villas, townhouses, 3-4-storey houses and 5-6-storey houses. We have calculated four product types based on factors such as product type, floor area ratio and selling price (this is a complicated process, so I won't go into details here). The final result is that the low-rise residential buildings and townhouses with plot ratio of 0.9 and 0.7 have the highest cost profit rate.
(See table below)
Volume rate, price, unilateral comprehensive cost, total profit (10,000 yuan), cost profit rate
Double spelling 0.45 6500 55991094216.08%
Series connection 0.7 5000 42181486218.55%
Low level 0.9 4300 35921770419.72%
Multilayer1.2 3600 30581843017.73%
However, if all products are positioned as these two types according to market requirements, the coverage of customers is still limited. In order to reduce the market risk, the product type should be combined with 5-6 floors of multi-storey residential buildings, and the floor area ratio can be between 0.7 and 0.9. We initially set the plot ratio as 0.8, and the product types are mainly townhouses and low-rise multi-storey houses, so that the interests of developers are most guaranteed.
On the other hand, this calculation result proves that this project should not be a residential area with a single product form, but a low-density residential area with single-family villas, townhouses and multi-storey apartments. When calculating the floor area ratio and architectural form, they must be calculated separately, which is different from the ideal state mentioned in the last article. But from another point of view, it also promotes some deficiencies in this calculation method. For example, because of the different architectural forms, the partition calculation method is inevitable. Each group calculates its own total construction area, land area and plot ratio, so that we can deal with the problems of roads, greening and public construction respectively, and finally ensure the accuracy of the calculation. The determination of the optimal floor area ratio has evolved into the determination of the optimal weighted average floor area ratio. In fact, it is also a question of determining the proportion of different types of residential areas. When this problem is solved, the design task book will basically take shape.