Incomplete Building Services Design (BSD) before the commencement of construction can arise from a myriad of factors, each with its own set of complexities. Here are several common reasons:

Insufficient or Unrealistic Timelines:

• The specifics regarding how timelines affect BSD were not directly available, but it can be inferred that unrealistic timelines might rush the design process, leading to oversights and incomplete designs.
• The pressure to meet deadlines can rush the design process, leading to oversights and incomplete designs which are common issues in the construction industry.

Budget Constraints:

• Limited budgets can hinder the allocation of resources needed for a thorough design process, making it a significant factor in incomplete Building Services Design.

Human Errors and Incompetence:

• Human errors, including design mistakes and omissions, are inevitable and can significantly contribute to incomplete designs.
• Errors in design, omissions, and workmanship deficiencies can lead to an incorrect or incomplete design which becomes a cause for disputes in construction projects1.
• Lack of design review during the design process and errors and omissions in design have been identified as causes of design change in building construction2.

Incorrect Processes:

• Lack of coordination between architects, engineers, and other stakeholders can result in overlapping or missing information in the BSD.
• Insufficient coordination during the design phase can adversely affect the BSD, especially in regions where this aspect of project management may not be well-developed3.

Complex or Lack of Clearly Defined Requirements:

• Design changes caused by plan alterations by the client, incomplete contract documents, and differing site conditions are also factors that can lead to an incomplete BSD2.
• Complex or unclear client requirements can cause delays or incomplete information in the design phase.

Insufficient Information:

• The lack of necessary information could result in design changes. A study explored the causes of design changes and proposed strategies to mitigate their occurrence5.
• Sometimes, the necessary information to complete the BSD may not be available or may change during the design phase.

Changing Regulations and Standards:

• Amendments in building codes or industry standards during the design phase can lead to revisions, potentially causing incompleteness in the design.

Technical Challenges:

• Technical challenges or unforeseen limitations can introduce errors or necessitate design changes, although the magnitude of this issue might vary from project to project.
• Technical challenges could include design errors which have been cited as a cause of variation in building project costs in Nigeria4.

Design Team Isolation:

• The isolation of the design team from specialists experienced in construction can lead to inevitable design changes in construction projects. This segregation may result in a lack of understanding or communication between the designers and the constructors, which can cause the Building Services Design to be incomplete or require alterations during the construction phase1.

Change in Scope:

• Changes in the scope of a project after the design phase has been completed can result in an incomplete or outdated Building Services Design. This can occur due to changes in client requirements, regulatory changes, or unforeseen project complexities2.

Design Management Issues:

• Problems related to design and design project management can lead to incomplete Building Services Design. For instance, a case study aimed to show how design and design management practices could be improved to prevent issues related to incomplete or ineffective design processes3.

Project Uncertainties:

• Project uncertainties can also contribute to incomplete Building Services Design. For example, a case study of a construction project failure due to uncertainties in France highlighted the importance of a well-defined project to avoid design and construction issues4.