Project cost is the construction price of the project, that is, the total investment required to complete a project construction. In recent years, China has invested a lot of money in building civil buildings to improve the living conditions of residents. How can we effectively control costs and make rational use of the country's limited resources? The key to project cost control lies in the investment decision-making and design stage before construction, and the key to control the project lies in design after project decision-making. The design of civil architecture is a design that specifically determines the standard structural form, the space and plane layout of the building and the reasonable layout of the building group according to the user's requirements for functions. How to make the design economical and reasonable and effectively control the project cost under the premise of meeting the functional requirements and national standards and protecting the safety of people's lives and property should be considered from the following aspects. 1. Planning and design of residential quarters. The standard design of residential quarters must meet the basic needs of people's living and daily life. On the premise of saving land, we should not only create a convenient, comfortable and beautiful environment for residents' life and work, but also reflect its unique style. According to the basic functional requirements of the community, the planning and design of the community should determine the reasonable levels and relationships of various components of the community, and accordingly arrange the layout of residential buildings, pipe networks, roads and green spaces, determine the reasonable population and building density, residential spacing, building floors, rationally arrange the scale and service radius of public facilities, and the supply of water, electricity, heat and gas, and divide the investment ratio of the above parts, including land. Finally, according to the land use index, density index and cost index, the economic rationality of residential planning and design is evaluated. 2. Layout of residential buildings. In multi-storey residential buildings, walls account for a large proportion, which is the main reason that affects the cost level. To measure the wall proportion, the wall area coefficient (wall area/building area) is commonly used. Minimizing wall area coefficient is closely related to the composition of high-rise units in residential building layout. Reasonably increasing the depth of the building and reducing the length of the external wall is one of the main measures to reduce the area coefficient of the wall, reduce the cost and improve the economic effect. With the same building area and different plane shapes of residential buildings, the building perimeter coefficient (that is, the length of the external wall per square meter of building area) is also different. Round, square and rectangular T-shaped increase in turn, that is, the external wall area and the decorative area of the internal and external surfaces of the wall foundation gradually increase in turn. However, due to the complexity of circular building construction, the construction cost is 20%~30% higher than that of rectangular building. Therefore, the reduction of wall engineering can not reduce the construction cost and bring inconvenience to users. Therefore, generally building rectangular and square houses is not only conducive to construction, but also reduces costs and is convenient to use. In rectangular residential buildings, length: width =2: 1 is better. Because the number of houses has increased to a certain extent, it is necessary to set expansion joints of two-story partition walls; When the length exceeds 90 meters, you need to pass through the aisle. These will increase the cost, so it is more economical to use 3~4 residential units and the length of the house is 60~80 meters. On the premise of satisfying the function and quality of the house, increasing the depth of the house, that is, adopting large width, has obvious effect on reducing the project cost. 3. The height and clear height of the house. The height and clear height of the house directly affect the project cost, because the increase of height and clear height, the increase of wall area, the increase of column volume and the heating of foundation pipeline also increase the cost. When the story height is reduced from 3 meters to 2.8 meters, the average comprehensive cost of each house is reduced by 4%-5%, and it can save materials and energy, which is beneficial to earthquake resistance. So the height of the house can't exceed 2.8 meters. 4. Connection of residential floors. Civil buildings are divided into low-rise, multi-storey and high-rise houses according to the number of floors. Generally speaking, in small and medium-sized cities, it is more economical to build multi-storey houses, which has the advantages of reducing construction costs and use costs and saving land. In big cities, some middle and high-rise houses can be built along the main streets to make use of space and beautify the city. 5, the composition of residential units, huxing and huxing area. Whether the composition of residential units is reasonable is an important issue related to applicability and economy. The room size and room combination of each unit should be determined according to the composition and occupation of family members. Building type refers to how many bedrooms each household has, the combination mode and the reasonable layout of kitchen and bathroom. Huxing composition and Huxing design should minimize the structural area, increase the effective area, increase the usable area of the house at the same time, and reduce the proportion of interior walls and partitions in the construction area. 6. Design choice of residential structure and building materials. The main building structures are: assembled structure, cast-in-place structure and assembled monolithic structure. And all kinds of building materials. Under the condition of meeting the structural requirements, the most economical and reasonable structural forms and building materials should be adopted according to the actual situation and local conditions. In this way, the design scheme is optimized from these aspects, and the engineering cost of civil buildings is controlled in the design stage.