Roof garden is a special garden form. It is a form of space greening and beautification relying on the platform at the top of the building to store water and cover soil and create a garden landscape. It involves architecture, agriculture, forestry and horticulture, and is a systematic project. It must be comprehensively studied and treated from the aspects of design, material selection, construction, management and maintenance.
Overview of design examples
In recent years, there has been an upsurge of roof greening in Chengdu, and the government has issued relevant regulations on roof greening: in the future, all construction projects in urban areas should be equipped with attached green spaces according to the planning requirements, and the attached green spaces should be mainly plants, and the greening planting area should not be less than 75% of the total green space. At the same time, large public buildings should build roof gardens under the safety requirements of public buildings.
A teacher is quite satisfied with the second-hand house he bought in a neighborhood near Yucai Middle School for 340,000 RMB. The reason is that the second-hand jump floor is not only twice as large as the previous residential area, but more importantly, the roof garden of nearly 70 square meters is more satisfactory to him. On the basis of consulting a large number of relevant materials and combining with the opinions of the owner on the investigation site, the author made a bold attempt design. Finally, when submitting the scheme, the owner put forward valuable opinions on the scheme. On the basis of comprehensive analysis, some problems that should be paid attention to in roof garden design are summarized.
The load problem is that the whole cast or prefabricated reinforced concrete roof slab should be used as the structural layer, and the "ecological roof block" made of heat insulation, seepage prevention and water permeability materials can be used if possible. In general, it is necessary to provide an additional load capacity of more than 350kg/m2. At the same time, in the specific design, in addition to considering the static load of the roof, factors such as non-fixed facilities, people flow and natural forces should also be considered. In order to reduce the load, pavilions, corridors, flower beds, pools, rockeries and other scenic spots with heavy weight should be designed in load-bearing structures or in locations with small spans, and artificial soil, peat soil, humus soil and other light materials should be selected as far as possible. The building structure should be considered in the form of roof greening, and the allowable load-bearing of the roof should be the design basis. The allowable bearing capacity of the roof must be greater than the maximum humidity weight of the planting layer with a certain thickness, the weight of the drainage material with a certain thickness, and the weight of plants and other substances. Knowing this, we should design roof gardens with different functions according to the actual bearing capacity of the roof.
Waterproof and drainage is the key to ensure that the plants planted on the roof can not only grow, but also be waterproof and drain the accumulated water to meet the building's use function. If leakage occurs, the whole roof must be redone, which is not only a large amount of work, but also a high cost. So waterproof and drainage is the most important problem after solving the load problem. This design adopts 1: 2.5 cement mortar to lay a leveling layer with a thickness of 20mm ~ 30mm；; Use 3 mm thick APP polyester coil and 3 mm thick anti-root coil as waterproof layer, and use 1: 3 cement mortar as 30 mm thick protective layer; Make a good drainage layer with pebbles, with the thickness of10cm ~15cm; 250g-300g polyester non-woven fabric per square meter is used as the filter layer; Finally, the plant soil layer is 25 cm thick. With this material selection and construction, the leakage problem of roof garden can be cured.
Waterproof treatment of roof garden
Deng Tianning, director of the Waterproofing Committee of the National Building Association, believes that the waterproofing of roof gardens is one level higher than that of ordinary houses, that is, there are at least two waterproof layers and two flexible waterproof layers. Ye of Beijing Institute of Civil Engineering and Architecture divides the planting roof into seven layers: planting medium, isolation filter layer, drainage layer, anti-rooting waterproof layer, coiled material or coating waterproof layer, leveling layer and slope-finding layer. The isolation filter layer is between the planting medium and the drainage layer and is made of non-woven fabric or glass fiber felt, which can be permeable to water and prevent soil loss. The lower part of the isolation filter layer is a drainage layer, which can be composed of special plastic drainage plates, rubber drainage plates or pebbles with a particle size of 20-40mm and a thickness of more than 80 mm, with sufficient clearance and certain bearing capacity. Cut off the root system with a waterproof layer resistant to root penetration, so as not to destroy the waterproof layer. Aluminum alloy coil, high-density polyethylene and low-density polyethylene geomembrane and polyvinyl chloride are usually used as waterproof layers against root penetration. The waterproof layer of coiled material or coating film is 1 ~ 2 layers of coiled material (such as polymer coiled material) or flexible waterproof layer of waterproof coating, which is water-resistant, corrosion-resistant and mildew-proof, and has strong adaptability to expansion or cracking deformation of the base. The leveling layer is leveled with cement mortar and covered with a flexible waterproof layer. The purpose of finding the slope layer is to quickly eliminate the accumulated water on the planting roof, so it is appropriate to find the slope with the structure, and the slope should be 1% ~ 3%.
Roof garden drainage
The design and installation of drainage system in waterproof layer is very important, which will directly affect the waterproof problem. Generally, it is discharged to the roof drain or drain pipe through the slope of the roof. If the drainage is not smooth, it will cause root rot of plants.
In the choice of planting soil, the key planting medium is the soil layer where plants planted on the roof grow. Due to the limited bearing capacity of the roof, the required planting substrate should have the properties of light weight, no hardening, water and fertilizer conservation, suitability for plant cultivation and growth, simple construction, economy and environmental protection. Generally, planting soil, peat, expanded vermiculite, expanded perlite, fine sand and fermented animal manure can be selected and mixed according to a certain proportion. Peat can be used as the main cultivation substrate, and its bulk density is very small, generally between 0.2 and 0.3g/cm ~ 2, while the bulk density of ordinary soil is 1.25- 1.75 g/cm ~ 3, and the wet weight is about1.9-2./kloc-0. It can be concluded that peat is 18-20% of the weight of ordinary soil in dry weight and 33% of the weight of ordinary soil in wet weight. If the roof garden uses 100% peat, the weight can be reduced by 2/3-3/4. Of course, it is impossible to build a roof garden entirely from peat. On the one hand, the relative cost of using peat is relatively high, on the other hand, the biggest disadvantage of using peat is that it is not strong enough in wind resistance and root fixation. Therefore, in practical use, roof gardens are generally built by infiltrating one part of peat into two parts of ordinary soil to make mixed soil. Or a proper amount of bran ash can be added. This can not only reduce the weight of soil foundation by 25-30%, but also improve the permeability and nutrients of soil foundation. Therefore, peat is an ideal material for building roof gardens. The planting layer thickness generally depends on the plant species: herb 15-30cm, flowering shrub 30-45cm, big shrub 45-60cm, shallow-rooted tree 60-90cm, and deep-rooted tree 90- 150cm.
One problem should be paid attention to when designing a roof garden-the load is limited. Roof gardens are often higher, so the wind is stronger. In addition, the roof has thin soil layer, long illumination time, large temperature difference between day and night, low humidity and low water content. We can choose some flowers and trees that like light, have large temperature difference, are cold-resistant, heat-resistant, drought-resistant, barren-resistant and have strong vitality. It is best to use shrubs, bonsai, turf and other plants. In short, tree species with many fibrous roots have developed horizontal roots, which can meet the requirements of shallow soil layer. Try to use as few tall trees with main roots as possible. If you want to use big trees, the planting position should be designed at the position where the load-bearing columns and walls are located, not on the roof panel. It should also be noted that the planting soil on the roof is lighter, the roof is higher, and the wind resistance of tall trees is obviously weaker than that on the ground. Therefore, reinforcement measures should be taken to facilitate the normal growth of plants. We can use soilless lawns and plants with fragrance and color, so that we can smell the flowers without going out. There is a slope transition between grass and shrubs. Finally, it should be noted that there are few trees, shrubs and herbal flowers on the roof. When designing, it is necessary to ensure that the flowers and trees are scattered at random and the colors are harmonious and reasonable.
Further thinking on the design of roof garden
Make full use of existing resources
For second-hand houses, there are more or less some old items that can be discarded lightly, but for large items that are lost again and feel pity, we should consider how to make rational use of them.
In the roof garden designed by the author, there is a reservoir made of fiberboard, which has been abandoned. It is about one meter high and has a lid. In the design, the author added a wooden pool with a height of 60 cm, a width of 40 cm and a length of 80 cm, removed the cover of the original pool, and decorated its outer surface with 12 cm clear water bricks. Two pools, one high and one low, one brick and one wood, are all natural materials, which are still precious in reinforced concrete cities. The author and the owner are quite satisfied with the transformation design of this sketch, and the promise on the spot will definitely become a reality, which is the greatest encouragement to the author. Name it a fish pond!
In the potted area designed by the author, the original resources were used to build potted containers. Simple, concise and beautiful is the owner's evaluation, which is also my design concept!
Start by knowing the owner.
As far as the family roof garden is concerned, its key service object is the owner of the house, so the designed things must meet the needs of the owner, just like a tailor making clothes for others. How to do this? Need to have a full understanding of the owner. The author believes that the understanding of the owners includes their family composition, personal preferences, industry and so on.
Perfect combination of modern science and technology and ecological science
With the rise of "roof garden fever", greening materials and technologies in special places such as roofs and balconies came into being, creating a "three-dimensional greening industry". The famous Japanese Misawa Housing Company, Kashima Construction Company and Teru Shimada Company all actively participated in the research and development of roof garden greening industry, introduced many new technologies and materials, and promoted the development of three-dimensional greening industry. Japan's largest waterproof material manufacturer has also developed "roof waterproof greening system technology", which consists of waterproof protective layer, drainage layer, filter layer and light soil. All materials are produced from waste materials, which improves the utilization rate of resources. Returning to nature, harmony between man and nature is the reflection of people who are fed up with urban public hazards. Only by combining modern science and technology perfectly with ecological science can we do more and better in roof gardens.
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Roof greening can increase the area of urban green space and improve the deteriorating human living environment space; Improve the urban heat island effect brought by high-rise buildings and the harm of sandstorms and various waste gas pollution to human beings; It can open up human green space, build an ecological city, improve people's living conditions, improve the quality of life and beautify the urban environment. If it can be well used and popularized to form an urban aerial greening system, it will greatly improve the urban environment.
References:
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[5] Zhang. Garden green space design [M]. Beijing: China Labor and Social Security Press, 2004.
[6] Zhao Dingguo. Roof Greening and Light Flat Roof Greening Technology [J]. Building Waterproofing in China, 2004 (4): 17-20.
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[9] Francisco. Asensio. Chievo Business Garden and Roof Garden [M]. Jiangsu: Science and Technology Press, 2002.
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