Nowadays, the old city is facing difficulties such as high building density, large population and complex house bases, especially in the original community, where there is a large amount of self-governance. Residents will carry out a large number of non-standard self-build behaviors, such as building terraces, in order to meet their living needs. This paper classifies and studies the terrace space in old communities in Tiantai County, proposes feasible construction strategies to alleviate this disorderly self-built phenomenon, and provides reference and guidance for future residential design.

1 Phenomenology-based analysis and research on the use of residential terrace space in old urban areas of Tiantai County

1.1 Overview of community housing in the old city of Tiantai

1.1.1 Old city status and regional selection

The Old Town of Tiantai County is the original urban area enclosed by the original city walls and consists of four original residential districts. As the city expanded outward, the original neighborhoods became neighborhoods with a more defined regional scale. These residential areas are dense and have implicit neighborhood boundaries. With urban construction, establishing commercial residences blurred the neighborhood boundaries and built bridges between communities. In this paper, we will study the community residential terraces in the old city of Tiantai County and discuss how to improve their utilization rate.

Unlike the grid-like residential areas outside the city, the home base owners built the residences in this area spontaneously. Thus, the plan shapes vary, but the residence types are generally similar. While visually, it may give the impression of spatial disorder, the overall space has a unique social structure, cultural ecology, and spiritual significance. The area's architectural history spans several eras, including courtyards and four-story buildings with mostly sloped roofs and roofs covered with clay tiles, which, in addition to the influence of Jiangnan culture, is dictated by the limitations of construction technology and cost. Later construction of the house, due to the influence of the place, also still retains the sloping roof structure.

The forms of the residences interact with each other, forming a strong symbiotic relationship. Because of the irregularity of the road on the north side and the lack of obvious through roads, this phenomenon is more obvious and organic in the Leaping Dragon Gate neighborhood in the north block, where the houses are self-built according to the situation of the residential site of the place, and most of the house facades have traces of secondary or even multiple self-builds. These self-built behaviors are partly to satisfy their own residential needs, and partly shaped by the large group of foreign tenants. The Yuelongmen neighborhood is more vivid than other plots, and therefore was chosen as the subject of this study to explore the characteristics and significance of these private self-build behaviors.

1.1.2 Types of housing in the old city

Through ground visits and drone forensics, five types of building plan were extracted from the abstraction of residential plan types: Point, Strip, L-shaped, Convex and Concave, and on this basis, the types were subdivided again according to the different spatial shapes in the site to obtain 25 residential types.

1.2 The current situation of community residential terrace space use

1.2.1 Analysis of community terrace types

According to the classification, the existing buildings in the area can be divided into 25 types, among which 19 types have terrace space, and most of the existing residential buildings have one or even more terrace spaces. Most of the residences in this residential area have additions, and the additions are mostly concentrated in the courtyard and terrace areas, and the self-built types are abundant and large in number. The study of the spatial types is universal for the study of the self-build behavior of this type of high-density residential space.

One of the courtyards is mostly used to increase the use space on the first floor. The masonry additions are designed to meet the needs of the second floor while also bringing a terrace space to the second floor. The use of the terrace and the addition are more outward-looking than the courtyard, and the openness of the space and the white space in the vertical direction bring the residents infinite reverie of using and building. According to the research, the use of the terrace space in the premises can be divided into four categories: vacant; planting or other use; partially built; and fully built.

The established types of terraces can be classified according to the above: four-sided open terraces, open terraces, stairwell intrusion terraces, three-sided open terraces, as well as semi-enclosed terraces and single-sided open terraces.

Among them, the vacant category exists in all types. The planting category is mostly found in the stairwell intrusion type terrace, the three-sided open terrace, and the semi-enclosed terrace, which is created mostly by creating close to the edge and away from the shaded functional space. They are also created by using part of the existing walls.

Partial construction is present in all construction types, but its presentation varies much. Some decks are fully open and are usually built with solid masonry construction, built close to the stairs. Other types of decks are constructed in masonry construction, light steel sunrooms and light steel skin shade houses. These are often constructed along the edges of existing buildings to the outside, but some are also built freestanding.

The fully constructed category is mainly found in the first three types of decks, where the first two types of decks are dominated by masonry construction, while the three-sided open and semi-enclosed types have sunrooms and shade rooms as additions, and both sunrooms and shade rooms have enclosed and open types. The construction mode is built with direct cover construction.

1.2.2 Analysis of the current situation of community terrace use

The use of observation decks requires consideration of the community environment and the impact of individual behavior on the group, and the status quo is not just a visual representation, but is influenced by a large number of objective and practical factors.

There were 352 terrace households into the research site: 18% of the terraces were vacant, with elderly people living alone and family groups making up the majority; 41% of the terraces were mainly used for activities such as planting and drying and stacking miscellaneous items; 25% of the households would build; 16% of the terraces were completely built, with glass and iron being the main ones.

People's habits and their pursuit of a good life are key factors in determining how a space is specifically used. Observations such as the use of the terrace and the use of the exterior of the home and the courtyard provide insight into the way the occupants live in the place and their standard of living.

1.3 Analysis and evaluation of community residential terrace experience based on phenomenology

1.3.1 Experience and response

Parasma believes that architecture is not only a visual seduction, but also a medium for transmitting and projecting intentions. The inhabitant chooses to use or abandon the terrace space according to the information he receives about the place and the reflection on his own dwelling. The terrace is one of the boundaries that shape the home, and its long-term use and creation is an outward expression of the resident's impression of "home" and an evaluation of the image of the place in which he lives. This act of creation strengthens the residents' experience of existence and reinforces settlement.

The occupants use the space according to their objective conditions and needs. The influence of the concept of living under this scale also determines the scale of the residents' creation of the terrace. As Rasmussen said, "Vernacular architecture seems to be born of the senses of muscle and touch, not of the eye." Unlike experiencing a new space, this experience of space is an unconscious experience with life as the main purpose.

The choice of form is based on the resident's realistic projection of the concept of home, and the memory of visual experience is important, but the formation of a specific space relies on the resident's comprehensive perception of the home. The occupants' sensory needs and sensory impressions of the surrounding places further determine the specific use and creation of the terrace space, which is a perceptual perception and response of the occupants to the place and themselves.

Human perception interacts with space as a result of the inseparability of time and space, as well as memory in human existence and experience. The brain converts spatial experiences into memories and again into experiences. Recollection is a repeated experience that utilizes existing experiences and is subjective. Unlike a filmed image, a memory can shape a scene in the mind, and the perceived "I" exists in that scene. In perception, the memory of experience can be used to reproduce the experience. Thus, perception is the sum of past to present experiences, and this "sum" is a logical progression of perception.

Architecture assumes more of a service nature than other arts, and Ponto also sees it as a container, similar to a canvas. But this container does not depend entirely on the will of the architect, but on the occupants. When the space becomes their residence, they are free to express their artistic preferences within it. Architecture is an interactive art completely different from other art forms, and the terrace demonstrates the results of the interaction between architecture and the city. As a space connecting inside and outside, the terrace directly influences the shape of the architectural interface and street space, almost completely shaping the living space and daily life of its occupants. Thus, architecture is not just the shape of the exterior, but the shape of people's lives around and within it. Unlike other interior spaces, the boundaries of terrace spaces are open and not easily perceived. When the terrace space is altered by the act of architecture and forms a boundary, the experience of sensation is intensified and psychological scale is added. This spatial non-specificity and people's preference for concrete space is one of the reasons that prompted the transformation of terrace space.

1.3.2 Perceptual experience under different terrace creation

Different construction methods can affect the perception of space for the same type of deck. Different sites and different deck designs can also affect the perception of space. This perception is objective and not good or bad. The authors have chosen some representative spaces to analyze each area.

1.3.2.1 Perceptual experience of creation and reinforcement - stairwell invasive terrace partial planting

The residence is located in the middle of the site in the southwest. The residence is a single-family house built from the reconstruction of a part of the foundation of a courtyard, with white wall tiles on the main display surface, its volume is large and the interior functional space of the building is complete, and there is no need to add a terrace. There are three terraces located on the second and top floors of the house. The two terraces on the top floor are at two horizontal levels, connected by a flight of steps, and the lower terrace is located on part of the roof of another house.

Occupants grow different plants in the building's two terraces. The larger terrace is located at the top of the building and uses the daughter wall on the south side of the home to create an enclosed space for growing lotus flowers with netting. The smaller terrace is planted with cucumbers and is supported using a climbing frame made of bamboo. The north side terrace has a planting area built along the side of the railing wall and planted with eight pots of plants, while leaving a space for a person to pass through. The lower west side terrace was planted with corn and a planting area was constructed using hollow bricks.

The residence is elevated above the surrounding buildings with two terraces offering different views and sensations. The white smooth floor tiles create a strong visual contrast with the wall tiles, brushed stone walls and clay tiles, adding to the tactile stimulation. Residents are able to perceive different light and shadow elements while enjoying the surrounding landscape from the different heights of the terraces, enhancing their sense of self-presence. The non-homogeneous texture of the surrounding area makes the light and shadow of the site complex and fragmented, and this visual perception of the relationship between light and shadow connects the place and "I" and strengthens the presence of "I". By planting plants to connect the terrace with the outdoor environment, the occupants gain a rich sensory experience, such as smell, taste, and the sense of smell and hearing in the environment. This visual perception of the relationship between light and shadow connects the place and the individual, reinforcing the sense of self-existence.

1.3.2.2 Reinforcement of boundaries and multi-sensory stimulation - complete planting and construction of semi-open terraces

This case is a four-story, single-opening dwelling located in the middle of the site. The foundations to the north and south were not utilized, while the open space 20 meters north of the building was divided among the neighbors for planting. However, the homeowner did not use the two vacant lots, but used the terrace and roof for planting. The homeowner's self-limitation is a manifestation of a strong identification with the home and a distrust of ambiguous, non-explicit space. At the same time, the neighbors are the original residents who have lived together for a long time, and the consensus reached with them about the vacancy of the foundation shows the self-identification of the residents with the site.

The terrace becomes the main place where the occupants receive their daily light. The terrace is covered with a light-transmitting glass roof, with a one-person high cabinet on the south side and a tiled floor further defining the boundaries and properties of the space. The terrace is ventilated to meet the needs of the residents for planting, and the planting units and enclosures of various materials, the touch of soil and wind, the smell of vegetables and cooking from the neighbor's house reinforce the real presence of the residents in the act of planting.

The homeowner enclosed an L-shaped area at the roof for planting. The terrace and roof use up almost all the space for planting, limiting the function of the space and the activities of the inhabitants. This mix of unique perceptual experiences, though primitive and dangerous, not only creates and evokes memories of a community or individual, but also increases the sense of belonging and identity of the inhabitants. At the same time, it brings a new possibility and option for urban life.

1.3.2.3 Boundary reinforcement and perceptual clustering - fully constructed semi-open terrace

In this case, the terrace is located on the roof of a home on the outskirts of the neighborhood. The homeowner removed the existing sloped roof, then enclosed the terrace and built a steel-framed enclosed sunroom. The renovation transformed the original three-story home into a four-story home with a mono-sloping terrace (sunroom) that receives sunlight from the top and east sides, and a ping-pong table in the center for activities.

In this case, the residents have covered the top terrace in its entirety, enclosing a clear boundary of space that facilitates the experience and perception of space and enhances reflection on oneself. The top is completely covered by glass, making the space weatherproof with even light during the day for drying clothes and playing ping pong. The top floor serves as a non-partitioned space, with internal transparency and height providing a venue to support the sport of ping pong, and the limited boundaries and uniform visual perception further enhance the experience of movement. It also reduces the impact of sports sound on the surrounding neighbors.

1.3.2.4 Associative association under limited perception - partial construction of invasive terrace along the street stairwell

This is a single-opening frame dwelling located on the southwest street side of the site, with the staircase located in the northwest corner of the building. The terrace is a stairwell intrusion, and the owner added a sunroom to the east of the terrace to preserve some of the space. Several potted plants are placed on the outside railing of the deck, and a granite laundry table is placed near the sunroom side. In summer, the roof of the sunroom is covered with a shade cloth. On the west side of the terrace there is a rubber swimming pool with a water pipe above the pool for filling.

The main living space of the building is on its eastern side. In order to maintain the consistency of spatial function and scale, the eastern side of the terrace was built as a sunroom, replacing part of the terrace space. This is an adjustment according to the occupants' living style. Although the terrace is reduced in size, it retains its connecting properties. The occupants can generate imagination through association, collage and complement the places, thus compensating for the restricted visual information.

1.3.2.5 Self-limitation and intensification of space and experience - stairwell invasive terrace fully planted

The case is located on the east side of the community, near the alley bazaar, and the surrounding buildings are high in the south and low in the north. The building is a four-story residential building with an overall strip shape and a large north-south depth. The terrace is composed of a stairwell intrusion terrace and a semi-open terrace. The stairwell intrusion terrace is fully planted and the semi-open terrace along the street on the south side is largely unused. The occupants' northern terrace is divided into two planting sites, north and south, both made of masonry. The northern site has a tree on the east side, greens and potatoes on the west side, and the southern site is set up with a netting required for sprawling herbaceous vegetables, with loofah seedlings climbing on it. Several orchid pots were placed on the east and west sides, and the center aisle was covered with recycled wooden boards.

The full use of the north side of the terrace depends heavily on the two factors of the stairwell opening facing north and the superior view of the north side over the south side, and the fact that the north side is connected to multiple buildings, making the act of planting safer. When residents enter the stairwell to go upstairs and leave the stairwell to enter the terrace, the terrace is the only space available. Therefore, it is more convenient for the residents to use the north side as the main area. Due to the height of the buildings around the site, the visual experience is better on the north side. The terrace landscape is enriched by the large number of greenery plantings, and its visual experience is further enhanced by the outlook provided by the north-facing view. The occupants restrict the spatial activities of the terrace to areas away from the street according to their needs, screening out some of the unacceptable sensory experiences. This filtering of planting behaviors, areas and experiences also self-limits the boundaries of the space under the habits of the residents. The terrace itself remains outwardly infinite, and the multisensory access to information about the surrounding site is not diminished or limited.

1.3.3 Problems and evaluation

This non-standardized creation, while a safety hazard, also creates a diverse, complex, and organic community. This type of construction allows the texture of the community to continue to evolve in multiple dimensions, further enhancing the perception of place as a daily practice of autonomy, as it is built by the residents of the community according to their own wishes. This act of natural construction is the result of subjective choice and identity, a growing process of construction. Through a comprehensive analysis of this building phenomenon, a group growth phenomenon can be identified. And by organizing these urban conditions accordingly, one can discover the most formal dimensions of people's survival and the reality of their living needs in the present.

1.4 Chapter summary

This chapter studies the terraces in old residential areas in urban areas of Tiantai County and classifies their forms and creation forms. By analyzing the problems of different types of terraces and their solutions, the relationship between architecture, place and people can be better understood. The authors find that the following problems exist in residential terraces in the old urban communities of Tiantai County:

1. unauthorized construction and additions affecting the aesthetics and structural safety;

2. Irregular planting leading to safety hazards;

3. long periods of inactivity leading to roof leaks;

4. the purpose of use is not consistent with the experience;

5. Disorderly use of materials affects the use and appearance of the city, increasing safety hazards;

6. Insufficient space to meet demand;

7. Lack of usage ideas leads to idle or disorderly usage.