Does design variability influence building costs?

 

In the construction industry, topic related with costing is frequently concerned party involves, including design teams, builders, clients and of course quantity surveyors. For the vast majority of construction client, building costs are their top priority. “What will it cost me?” or “Can we do it any cheaper” are two of the most popular question initial queries by clients. One of the main goals of quantity surveyors is to estimate the expected cost of construction work and manage the changing project design to prevent going over the client's allowed budget. This is a difficult undertaking that frequently entails one-of-a-kind, custom buildings constructed with specific purposes, and the QS typically works within a design team assembled especially for that project.

Design Variable

Design variables can be refers to quantitative source that is enables to modify any design to make it more ideal. Therefore, they comprise the architecture aspects that affect the price of construction work. In addition, they also help in predict outcomes since the building design variable provides the data needed to predict consequences and assess if value can be obtained at a reasonable cost. Providing solutions to issue related of shape, time, performance, budget and economy for structure as a foundation for decision-making. This is attributable to the fact that they accurately reflect how expenditures are incurred in reality.  

Building expenses are impacted by several variables, some of which are interconnected. The financial implications of alterations to a building's shape, size, storey heights, overall height, fenestration, and other aspects. The element of design indeed will be affected by the user’s preferences, planning and building regulation, aesthetic standards as well as structural design that directly might influence building cost.

What factors influence the design variability?  

1. Shape

According to standard definitions, shape stands for the spatial components that creates the building’s form. It affects the areas and sizes of vertical parts such as the walls, windows, partitions and the finishes applied, as well as the perimeter details such as ground beams, fascia and roof eaves. The cost of a structure is significantly influenced by its shape. In fact, the building’s unit cost will be lower as the simpler its shape is. Where building’s unit cost together with its perimeter will arise if it is longer and narrower or has more intricate and irregular form shape.

 

Moreover, an irregular design will increase expenses due to some other factors such as sitework, laying out and drainage work that will become more difficult and expensive. From the previous research has come with the same conclusion that plan complexity or irregularity will affect perimeter-to-floor ratio unit as well as overall project cost. This might because building’s form will generally impact the costing due to construction of building components including foundations, walls, the frame of building, finishes, roofing and others. It also will have impact to the operation and maintaining cost of building with significant impacts on the building’s overall life cycle costs. 

 

2. Average Storey Height

Storey height means level from one finished floor to the next, until to the ceiling or height above. Overall, the higher level of building is, so building cost per unit will increase due to many factors. Following are the things that could increase the cost:

1)     More durable service and waste pipe might be necessary.

1)     The expenses for circulation components like stairs and lift which depend on the storey height of buildings.

1)     The installation and application cost will rise.

1)     The amount of thermal energy may brow as a result of the building’s greater volume and the length that its supply cables.

  

3. Number of storey height

This factor actually directly similar with average storey height, where it is more relates on how high and levels need for the building especially in a vertical structure. The construction of tall structures typically has a considerable impact on four main building components which depend to the high-rise building’s amount of floor.  It involves of vertical element for the building which are frame structure construction, external wall, lift installation and fire protection. In prior research shown that construction costs will increases the number of stories rises. In fact, aspects that should be considering when high rise building are proposed is:

1)     Increasing the building’s composition which creating a huge floor area with great daylighting.

2)     Where the installation of another storey did not affect any building’s structural design.

3)     The unit cost that might typically increases as the method of construction changes. 

 

4.  Size

Size is approximate square metre value of the entire useable internal floor area of the residence as determined by the surveyor. It does not include areas behind partition walls or stairwell areas, integral garages, or stores that can only be accessible from the outside. The other words of size, floor area or floorspace is the area that be measured as square feet or square metres by the part of the building.

The methods for determining "floor area" rely on which building components, such as external walls, interior walls, corridors, lift shafts, staircases, etc., should be included or excluded. In general, there are three main variations in how floor space is measured.

·        Gross floor area (GFA) - Related to the exterior face of the exterior walls, the building's total floor area.

·        Gross internal area (GIA) - Measured from the internal face of the exterior walls to the total floor area of the structure.

·        Net internal area (NIA) (or usable floor area UFA) - The NIA is the GIA less the floor space occupied by lobbies, covered machinery rooms on the roof, staircases, and escalators, mechanical and electrical services, lifts, columns, bathrooms (other than those on domestic property), ducting, and risers.

5. Fenestration

Example of window’s opening

Fenestration is related to the openings in a building's facade or envelope. The placement and installation of the openings are also considered to be fenestration. Any component of a building's exterior shell known as the envelope helps regulate the building's climate by preserving a dry, warm, or cool internal environment. In fenestration architecture, there are three primary elements:

a)     Door

b)     Window

c)     Skylight

The term "fenestration" refers to anything that permits access from the outside to the interior. Latin for windows is fenestrae. Outside of architecture, there exist fenestrae. In actuality, the human skull has holes, called fenestrae, which lighten the skull without sacrificing strength. The skull would be substantially heavier and maybe weaker without these perforations. Like skulls, buildings have holes, which retain their strength without compromising their size or area.

 

The design of the window's fenestration should take opening requirements into consideration. For example, picture windows that are fixed in place do not open but still need offer a clear view and a lot of natural light. Some window fenestrations open on hinges, such as casement windows, while others are opened by vertical movement, such as sash windows.

 

Functionality is also impacted by fenestrations like doors. Doors allow for airflow, ventilation, and security. Doors must be positioned to give unobstructed access into a room and to swing open freely without hitting any barriers. Animal hides or textiles draped in an entranceway were frequently used as doors in the past. Revolving doors and mechanised doors are examples of technological advances. Additional fenestration in the form of skylights has developed. In the past, skylights were little more than holes drilled into dome ceilings, which enabled rain to enter structures.

6. Complexity of shape

Complicated design and features will take longer to assemble and may involve several processes, which increases the possibility of errors and flaws. The extend of repetition and compartmentation will also have an impact on the ultimate cost of the job. It can be said that simple planning and constructible solution might promote increasing plant usage, which leads to higher output and decreased waster. Irregular and complex shapes increased the costs considering the potential cost implication like

1)     The installation of irregular roof shape result in material waste and cutting corners.

2)  Increasing of setting out and time needed.

3)   Costing for excavation

4) Complex design might need extra manholes and longer pipe that directly impact drainage costs. 

 

Case Study 1

Plaza Shah Alam

Plaza Shah Alam

Plaza Shah Alam or known as Plaza Masalam is a shopping mall located at No. 2, Jalan Tengku Ampuan Zabedah E9/E, Section 9, 40100 Shah Alam, Selangor. The building was opened to public in 2007 which the operation hours start from 10.00 a.m until 10.00 p.m. The building place in middle of section 9 that has been emerged as a landmark in Shah Alam during the previous ten years. The mall consists 4 levels that include of lower ground floor, ground floor, first floor and second floor with parking area at roof top.

Lower Ground Floor Plan

According to the case study's findings, the building shape can be categorised as a rectangle building with the most basic design form. The building only had four levels, and it did not use a complicated line. Previous research has shown that the cost per square foot of a building decreases the simpler the building plan shape. This mall is also can be considered smaller than other ones that are already in existence, making the building's shape arrangement more effective and directly contributing to a decrease in energy efficiency. Overall, there are two ground-floor entrances: the main entrance and the back entrance. In addition, one door also connecting the building's interior to the parking lot is also available on the third floor (roof top).

Main entrance (Ground Floor Level)

Back entrance (Ground Floor Level)

Entrance from parking areas 

Case Study 2 

IOI Mall Puchong

IOI Mall Puchong

IOI Mall Puchong is a shopping mall located at Bandar Puchong Jaya, Selangor. The mall was opened in 1996 and it was built to serve the residents of Puchong whose numbers were small back then. It consists of 4 levels and a roof-top parking area. The Old Wing of the mall was managed by Jusco, which is now known as AEON. While the new wing expansion opened in 2009 for new tenants. The design of the mall gets inspired by Spanish and Colonial architectural influences. Beginning in December 2017, the mall completed renovations that included upgrading each area to a more contemporary architectural design and switching to LED lighting for all of the main lighting fixtures. After the mall was fully completed renovations, they started the operation by the end of 2018 from 10 am to 10 pm.

Ground Floor Plan of IOI Mall Puchong

According to the case study's findings, the building shape can be categorised as an L-Shape building for the whole and rectangular for most shop lots inside the building. However, there are three hexagons shape at the centre of the building which located at North Court (Old Wing), South Court (New Wing) and Carnival Court (in the middle). In addition, the building only had four levels with straight routes which were not complicated and easy to access from all directions. Thus, it makes a good airflow for fenestration from every access. Also, the total area of the mall was 650,000 sq. ft. before the extension, which now 3 times bigger than its existing. This also leads to higher costs in maintenance, utilities, and expenses services. Overall, there are seven ground-floor entrances from the surrounding building and two entrances on the rooftop.

 

The new wing of IOI Mall Puchong

Comparison

 

Factors	Plaza Shah Alam	IOI Mall Puchong
Shape	Rectangular shape with uncomplicated partition and compartment	L-Shape, rectangular (shop lot) and hexagon (north court, carnival court and south court)
Storey Height	4 levels of floors	4 levels of floors
Size	Small compared to other existing malls	650,000 sq. ft.- bigger than the existing building
Fenestration	There are 3 entrances provided	There are 9 entrances provided
Complexity of Shape	Basic form, did not have any complicated line	Most of the shop lots were rectangular, and only a few that has been renovated.

 

Based on comparison between the two malls, Plaza Shah Alam and IOI Mall Puchong, it can be seen that Plaza Shah Alam has the lowest cost and energy-efficient building. It is based on the factors of design variability that was applied, which includes of shape, storey of height, size, fenestration, and complexity of shape. In general, the cost is actually depends on the design of structure, where building with complex formed, curved or angular structure will cost more compared to straightforward design. So, in this cases, Plaza Shah Alam adapt a basic form with rectangular shape without any intricately formed compared to IOI Mall Puchong which modelled in L-shape form. In addition, the arrangement of Plaza Shah Alam designed with uncomplicated partition and compartment inside of building, which more straight-forward style. As opposed to IOI Mall Puchong, the layout of the mall for the shop lot is design to be rectangular with hexagon point in north court, carnival court and south court. According to previous study, shows that the additional expenses bought from structure’s increased depend to storey height which is due to the vertical components of a building, such as its walls, partition, columns and how the adaptation of its partition.

Typically, larger structure with straightforward, standard, rectangular floor plan and elevations will cost per less per square metre of floor area than smaller, intricately formed, curved or angular structure. However, when two case studies’ design variability is compared, they both respectively shows similar form. But then again, we can also observe that the size of IOI Mall Puchong bigger than Plaza Shah Alam, which had a total floor area of 650, 000 sq. ft, that indicates Plaza Shah Alam is less expensive. Following that, the fenestration factors show that IOI Mall Puchong had more openings, with 9 entrances, than Plaza Shah Alam, which had 3 entrances. In general, fenestration affects the stability of a building, but with advanced construction technology, it has become easier and thus, as a part of design and plans. The more openings in a building, the higher the costing of the construction. Lastly, another factor that affects costing is shape complexity, which is primarily determined by the architectural value of the building form. In this case study, neither used any tricky lines or forms, but IOI Mall Puchong is more complex and required some corner angles.

 

Conclusion

Based on both case studies above from Plaza Shah Alam and IOI Mall Puchong, we can summarize that design variability influence the building cost. This is due to the design structure itself where it can cost more when complexity of shape is developed to building appearance. The harder shape of the building, the higher cost needs for maintenance and services. Other than that, storey height also plays a vital role to the higher cost as there is an extra charge for vertical components to bring upstairs. Not only that, but fenestration also influences the building cost as most of the building needs it for airflow throughout the building. For instance, openings must be included in the building envelope for people to live comfortably within a structure or even enter and exit them in the first place. So more opening, the better environment for comforting people. While in terms of size, it shows that the smaller total floor area, the lowest cost for the building as it smaller size. Last but not least, between both cases tudies, Plaza shah Alam was less in term of costing compared to IOI Mall Puchong according to their design variability.

 

 

 

https://study.com/learn/lesson/what-is-fenestration-architecture.html https://www.matec-conferences.org/articles/matecconf/pdf/2017/17/matecconf_iscee2017_03019.pdf https://publikasiilmiah.ums.ac.id/xmlui/bitstream/handle/11617/6562/ICETIA2015%20-%20%2028.pdf?sequence=1&isAllowed=y https://link.springer.com/chapter/10.1007/978-1-349-17173-6_2 https://arrow.tudublin.ie/cgi/viewcontent.cgi?article=1028&context=beschreoth