Building Sizing – What are the Regulatory Constraints on Building Size?

building-sizing

Building Sizing – What are the Regulatory Constraints on Building Size?

Although building size will fundamentally vary depending on the production capacity of a pharmaceutical manufacturing facility, in general this type of building tends to occupy large areas and volumes due to the nature of the business (such as tall process equipment, high capacity warehouse storage, etc.). During facility design, it has always been a common question (and a subject of discussion with clients) as to what regulatory constraints on building sizing are to be taken into consideration. It is significant to understand the area and space limitations imposed by the regulations, as it has a major effect on the design.

For reasons pertaining largely to safety, the National Construction Code (NCC) introduced compartmentation to all Class 5-9 buildings, which intended to limit the spread of any possible fire in a building by dividing large buildings into fire-tight boxes, termed ‘fire compartments’. Each compartment is safely and completely enclosed – separated from the remainder of the building by barriers to fire (such as fire-resisting walls and floors). Therefore, in the event of an outbreak of fire within the building, a fire resisting enclosure will inhibit fire and smoke from spreading to another compartment or part of a building.

Depending on its size, a building may comprise single or multiple fire compartments. Based on the assumption that limiting the size (area and volume) of a fire compartment will limit the size of a fire in a building, the NCC sets out the maximum allowable floor area and volume for fire compartments. In determining the maximum size, two following factors are to be considered.

  1. Building classification – a measure of building’s potential fire load, and
  2. Type of construction – indicating building’s ability to resist a fire.

Buildings must be designed and constructed in a way to satisfy these limitations – meaning that size of any fire compartment (or atrium) cannot exceed the figures specified in Table 1 below.

Maximum Size of Fire Compartments or Atria
Table 1: Maximum Size of Fire Compartments (or Atria)

Example:

Layout Options
Figure 1: Layout Options

According to the figures set out in the Table 1, this pharmaceutical manufacturing facility of Class 8 with a total area of 3200 m2 can be:

  • Type A or Type B construction, as its total area falls within the maximum fire compartment size permitted, or
  • Type C construction if it is divided into fire compartments with areas not more than 2000 m2 or if it is a large isolated building.

For further information, refer blog Large Isolated Building.

What if it is a building of mixed classifications?

Though the code does not specifically cover maximum permissible floor area and volume for buildings containing mixed classifications, the NCC Guide provides a clear example of how we use the table above in that case.

Example:

This facility of Type C construction consists of:

  • A manufacturing area of Class 8, and
  • An office area of Class 5

The total area of the building is 2100 m2.

A Building of Mixed Classifications
Figure 2: A Building of Mixed Classifications

In order to calculate the maximum allowable floor area of this building (of mixed classifications), we need to go through the steps below:

  • Step 01: Determine the area breakdown of the facility to find out the area that each classification covers.

In this example, manufacturing area is 1680 m2, the office covers the remaining 420 m2.

area breakdown
Figure 3: Area Breakdown
  • Step 02: Identify the percentage of total floor area that each classification occupies.

In this facility, manufacturing takes up 80% of the total floor area, the office covers the remaining 20%.

Percentage of Each Classification

Percentage of Each Classification
Figure 4: Percentage of Each Classification
  • Step 03: By using the Table 1, identify the maximum allowed floor area for each classification.

For this facility of Type C construction, the maximum floor area allowed by the table is 2000 m2 for Class 8 (manufacturing) and 3000 m2 for Class 5 (office).

Use of Table 1
Figure 5: Use of Table 1

 

Maximum Allowed Floor Area for Each Classification
Figure 6: Maximum Allowed Floor Area for Each Classification
  • Step 04: By using the percentage, work out the proportion of the maximum floor area allowed for each classification.

In this example, we need to calculate;
⇒ 80% of 2000 m2 for Class 8 (manufacturing), and
⇒ 20% of 3000 m2 for Class 5 (office).

Proportion of Maximum Floor Area
Figure 7: Proportion of Maximum Floor Area
  • Step 05: Add each of those proportions (calculated above) together in order to reach the total maximum permitted floor area for the entire facility (of mixed classifications).
Total Maximum Permitted Floor Area
Figure 8: Total Maximum Permitted Floor Area

The result of the calculation above shows that the maximum allowable floor area for this building of mixed classifications is 2200 m2. As the total area of the building is 2100 m2, it complies with the Table 1 in terms of area limitation.

In this example, the manufacturing area (1680 m2) seems to exceed its portion of the maximum floor area allowed (1600 m2), which is not important for the purposes of this process as long as it does not exceed 2000 m2.

Are technical areas included?

If technical areas are located at the top of a building and they accommodate only service units or equipment (such as heating, ventilating, lift equipment, water tanks, etc.), then they are considered to have a low level of occupancy and fire load. Additionally, due to being the topmost storey of a building, an outbreak of fire within that area is unlikely to inhibit the evacuation downwards. Therefore, they are not counted in the floor area or volume of a fire compartment.

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