NYC building code 2003 Design of masonry wall clarification

[catnyc]

Hi,
section 6.4.1 Multi story buildings (page 129 volume II,RS-10 NYC Building code 2003) is not clear to me.
Regarding item a) Exterior Solid Walls-..."The thickness of solid exterior masonry bearing walls shall be at least 8 in. for the top floor and 12 in. for a maximum of 55 feet measured downward from the top floor level. Any addtional height should be provided by 16 in lower walls up to a maximum height of 104 ft. Building taller than 104 ft. shall be structurally analyzed and designed. The slenderness ratio shall not exceed 20. "

Question: where in elevation is the 16 inch wide wall required ? At 55 feet ? Please advise someone.

 

[haynewp]

I don't have that book but it sounds like it should be like this:

top floor: 8 inch (whatever height top floor is, say 10ft from floor to roof)

walls below top FLOOR: 12 inches, which can be used up to a maximum of 55 feet

Therefore the 16 inch would start at (10 feet+55 feet)=65 feet from the top of the highest floor.

I don't really like the phrase: "Buildings taller than 104 ft. shall be structurally analyzed and designed". To some people it may sound like "so up to 104' just put whatever reinforcing you choose."

 

[haynewp]

(16 inch starts at 65 feet from roof.)