Designing safety and security systems requires knowledge and skill – not only because of the high-stakes nature of these systems and the consequences of failure but also because security system design involves a set of tools and processes that require a high degree of technical competence. Security system design includes consists of drawings, specifications, project management, and a Basis of Design (BoD).

When designing safety and security systems, the organization’s security requirements can usually be met with multiple design options and approaches. Design professionals use a BoD to explain design decisions and capture their reasoning for choosing one solution over the others during the design phase of the project.

What is a Basis of Design?

A Basis of Design is a document written by the designer or engineer of record. It serves to capture many aspects beyond what you might find in specifications or design drawings and introduces narrative statements on the thought processes behind major design decisions. It provides the designer’s underlining motivators, and the “why” behind their design decisions.

The objective of the document is to provide the parties involved with a good understanding of the reasoning that led to the selection of a specific solution, integration, or equipment. It typically consists of the following elements:

• Objectives of the project. This includes the general business expectations, performance criteria that the system was designed to meet and the specific needs and requirements stipulated by the organization needing the design.
  
  
• Narrative of the design. This is a narrative statement that provides an explanation of why the specific systems, equipment, and integrations have been selected in relation to the stipulated objectives and criteria. This is the part of the BoD that documents the designer’s thought processes and motivations for choosing one system, approach, equipment, or integration over another. It could also incorporate the reasoning why other options have been eliminated or any system design constraints that must be taken into consideration.
  
  
• Selection of equipment. This is a narrative statement for each type of equipment, consisting of the manufacturer, make, and model, and the reasoning for selecting it. This encompasses the capabilities of the specific equipment, its features and benefits, and other deciding factors.
  
  
• Life cycle costs / total cost of ownership. Cost-effectiveness is an important consideration when building systems for safety and security. While multiple solutions might satisfy the criteria and objectives of the project, these options have differing initial costs, installation costs, operating costs, and maintenance costs.
  
  The BoD contains economic considerations taken by the designer when choosing which equipment or system to be used in the design, comparing total cost of ownership to the total expected benefits of the available solutions.
  
  It might show the tradeoffs between having a low initial cost of one solution versus the long-term cost savings of another over time for a better return on investment. With this comparison, the most cost-effective system can be identified.
  
  
• System operation and maintenance expectations. The BoD verbally details how the system is expected to operate under various situations, taking into account normal operations, alarm events, and power outages. This provides a baseline for operational expectations once the system is up and running, as well as utility sources, energy performance, and emergency functions.
  
  It also incorporates the maintenance requirements of the system: routine maintenance procedures, the frequency of maintenance operations, and the staffing required to keep the system fully operational.
  
  
• Codes and standards. The BoD provides the codes and standards that are applicable to the project, as well as the design decisions made to make the system fully compliant. It documents the specific code numbers and editions used as a reference when designing the system.
  

Capturing the underlining motivators and the “why” of the direction provided is very useful in creating the attitudes and atmosphere surrounding the project. It will also allow an easier pivot to another solution if a better alternative becomes available in the future of the master plan. Thanks to technological advancements in the safety and security industry, it is also possible that the “why” might shift. Having the Basis of Design design as a point of comparison will assist in adjustments to the solution if necessary.