Code considerations for a 6 or 7 story building

[Tim Mailloux]

We are meeting with a client tomorrow to discuss a new building on their campus. They have proposed a new 6 or 7 story office building (sloping site and the number of stories depends on grade plane determination) to conserve land on their campus, but we feel a smaller 3 or 4 story building with a larger foot print will be a more efficient building and also save cost. I have never worked on a new building over 4 stories, what are some common code considerations that come into play when you get above 4 stories. This is my current list:

• CT specific, at 6 or 7 stories this would considered a threshold building and will require an independent structural review by a 3rd party engineer, at the owners cost.
• 4 stories could be type 2B construction. Anything higher will require fireproofing the structure. 6 stories would be 2A and 7 stories would be 1B.
• The taller building will probably require a fire pump.

 

[steveray]

Egress elevators? Stairwell pressurization?

 

[Tim Mailloux]

stand pipes, an FCC (fire command center) will be required, standby and emergency power

 

[cda]

Are you or will you be a high rise

 

[Tim Mailloux]

Are you or will you be a high rise

almost certainly

 

[steveray]

With a "lower" construction type you may be limited to the uses you can put on the upper floors...For instance IIB no "assembly" above the 3rd floor....

 

[Tim Mailloux]

that shouldn't be a problem, but something worth pointing out.

 

[steveray]

Watch the large conference rooms on the "executive" levels...If it is an A3 >10% you might be done..Which gets harder with a smaller floor area...

 

[Tim Mailloux]

that shouldn't be an issue with this project, each floor is designated to a specific department and there is no executive level or large conference rooms over 750sf in the program. And if we can convince the client to lower the building the footprints will become much larger making the 10% threshold even harder to reach.

Who know how they will use this building in the future and having the flexibility to add large A3 spaces above the 3rd floor in the future may be worth considering.

 

[RLGA]

Depending on where the lowest level of fire department vehicle access will be situated (high side or low side of the sloping site) and the floor-to-floor heights, the building may or may not be a high rise. If floor-to-floor heights are an average 12 feet and under, then you probably won't be a high rise at seven stories (6 stories x 12 ft. = 72 ft. < 75 ft.). If the building is six stories, then your average floor-to-floor heights will have to be less than 15 ft. At 15 ft., that would put you exactly at 75 ft. (5 stories x 15 ft. = 75 ft.), but the fire department vehicle access will probably be a few inches or even a foot or two lower than the first story elevation.

The nice thing about Type IB construction is that nearly all of the occupancy groups have an unlimited area (except for Groups H, some I, S, and U). That means no accessory occupancies and separated occupancies are required for a typical office building.

 

[Tim Mailloux]

Depending on where the lowest level of fire department vehicle access will be situated (high side or low side of the sloping site) and the floor-to-floor heights, the building may or may not be a high rise. If floor-to-floor heights are an average 12 feet and under, then you probably won't be a high rise at seven stories (6 stories x 12 ft. = 72 ft. < 75 ft.). If the building is six stories, then your average floor-to-floor heights will have to be less than 15 ft. At 15 ft., that would put you exactly at 75 ft. (5 stories x 15 ft. = 75 ft.), but the fire department vehicle access will probably be a few inches or even a foot or two lower than the first story elevation.

The nice thing about Type IB construction is that nearly all of the occupancy groups have an unlimited area (except for Groups H, some I, S, and U). That means no accessory occupancies and separated occupancies are required for a typical office building.

We are anticipating 13'-4" to 14'-0" floor to floor heights, its very challenging these days to get anything lower than a 13'-4" floor to floor height and not get stuck with 8'-6" ceiling everywhere. So even at 6 stories with 13'-4" floor to floors we will be above 75 feet, and based on the site my gut is telling me this is a 7 story building in the eyes of the code.

 

[RLGA]

We are anticipating 13'-4" to 14'-0" floor to floor heights, its very challenging these days to get anything lower than a 13'-4" floor to floor height and not get stuck with 8'-6" ceiling everywhere. So even at 6 stories with 13'-4" floor to floors we will be above 75 feet, and based on the site my gut is telling me this is a 7 story building in the eyes of the code.

For high rise buildings, it is measured to the height of the highest occupied floor and not to the average roof as it is with building height determination. Thus, a 7-story building is concerned with the floor-to-floor heights of the first six stories and for a 6-story building, it is for the first five stories. The measurement is from the elevation of the lowest fire department vehicle access and not the grade plane, so the fire department access may be slightly lower than the first floor elevation.

 

[Tim Mailloux]

The measurement is from the elevation of the lowest fire department vehicle access and not the grade plane, so the fire department access may be slightly lower than the first floor elevation.

The lowest level, or the Basement as the client wants to call it will have one side with an on-grade entrance / exit at the low side of the hill. The first floor main entrance / exit will be on the opposite side of the building at the high side of the hill. This will potentially be the lowest level of fire department access and would put the elevation of the uppermost floor at 78'-0" with floor to floor heights of 13'-0", the lowest we think we can make work.

So there is a good chance this is high rise building if we stick to the clients design scheme, and is most certainly would be a 7 story building in the eyes of the code.