Construction Type for Airport Traffic Control Tower

[ajmille305]

I getting involved with projects that are designing airport traffic control towers around the country. I know this type of building is modified under chapter 4 of the IBC for special detailed requirements. For 412.2 IBC 2021, there is a paragraph, and associated table (412.2.1.1; other editions have similar requirements) that specifies the type of construction that the tower will need to comply with based on the height to cab floor.

For a a tower with a cab floor height of 87 feet, this would require a Type IIA construction, cab floor plus roof could easily add 20 feet. Based on the allowable building height table in chapter 5 (Table 504.3) for an assumed B occupancy sprinklered tower, the allowable building height is limited to 85 feet. My interpretation, based on reading through IBC handbook commentary, is Table 412 is the driving factor and Table 504 is not applied. Taken to an extreme, a cab height of 99 feet would far exceed the height limitation from Table 504.

Is this a correct interpretation, or does Table 504 allow apply? If that's the case, how does Table 412 jive with Table 504?

 

[RLGA]

Per IBC Section 102.1, the specific requirement takes precedence over the general requirement. Table 504.3 is a general requirement for Group B occupancies, and Table 412.2.1.1 is specific to control towers. Thus, Table 412.2.1.1 takes precedence over Table 504.3.

 

[Paul Sweet]

Note a underneath Table 504.3 says "See Chapters 4 and 5 for specific exceptions to the allowable height in this chapter."

 

[RLGA]

Note a underneath Table 504.3 says "See Chapters 4 and 5 for specific exceptions to the allowable height in this chapter."

Good point.

 

[ajmille305]

Note a underneath Table 504.3 says "See Chapters 4 and 5 for specific exceptions to the allowable height in this chapter."

Footnotes are always my downfall. I always seem to gloss right over them.

 

[ajmille305]

Per IBC Section 102.1, the specific requirement takes precedence over the general requirement. Table 504.3 is a general requirement for Group B occupancies, and Table 412.2.1.1 is specific to control towers. Thus, Table 412.2.1.1 takes precedence over Table 504.3.

For the second part of this paragraph "Where, in any specific case, different sections of this code specify different materials, methods of construction or other requirements, the most restrictive shall govern."

Doesn't this negate what was written in the first part? I read this as Table 504 is the more restrictive and would apply.

 

[Joe.B]

 

[Joe.B]

 

[RLGA]

For the second part of this paragraph "Where, in any specific case, different sections of this code specify different materials, methods of construction or other requirements, the most restrictive shall govern."

Doesn't this negate what was written in the first part? I read this as Table 504 is the more restrictive and would apply.

I don't believe the second sentence was supposed to negate the first sentence. The second sentence states "different materials, methods of construction or other requirements," which I interpret to be limited to those types of conflicts and not broad code requirements, such as height, area, construction type, etc.