1. Egress & Core strategies
Building Planning…
Egress &
Core strategies

2. Example, multi-tenant office bulding
Key issues
Return on investment
Clear circulation/wayfinding
Maximize value of perimeter glass/views
Allow for street level retail
High net to gross ratio (what’s that?)

3. Net: What you can rent…
Face of wall to face of wall
The higher the net assignable square footage (NASF) the higher the income
Also used to compare efficiency between concepts
Gross: everything else
Stairways
Lobby
Toilets
Custodial
Mechanical/electrical
Wall thicknesses
Amenity spaces (workout/atrium…)

4. Some common net to gross ratios
Administrative buildings 67/33
Auditorium buildings 70/30
Courthouse 61/39
Hospital 55/45
Office buidling 75/25 (80/20 common)
Science building 60/40
Warehouse 93/7
The larger number is usually the net…those functions that are the reason to build the building
The smaller number is the net…those functions that serve the above.

5. … even star architects watch it very closely between schemes

6. Public/employee sequence dominates…but doesn’t locate
elevators
Lobby/Reception/directory/security
retail
retail
Double loaded lobby allows two retail tenants
Single loaded would allow one larger tenant
Challenge might be identity
Entry/vestibule

7. Other core responsibilities
Besides housing egress, access, toilets and HVAC, cores often act as the primary space definition elements on a floor.
They also are often used for lateral bracing of the structural frame, with walls reinforced to be shear diaphragms or with “X” bracing or chevron bracing concealed within their enclosing walls

8. Core location…always center?

9. Willis Tower, Chicago
53,000 net rentable s.f.

10. Empire State Designed for Rapid-Building
… 2,768,591s.f. in 410 days? 6,752 s.f. per day!
Standard Bay sizes
Standard Mullion spacing
Stone sizes fit to milling equipment
Steel sizes fit to transport/lifting equipment

11. Setbacks change floor plates
Meeting zoning required stepping back the building, reducing the number of repeated floors
Upper floors consumed by elevators (73 total)

12. End Core location responds to local conditions…view, climate…
What looks problematic?

13. Lever House, NYC,
Gordon Bunshaft, 1952

14. Multi Core placement for large floor dimensions (<300’)

15. Sendai Mediateque, Ito atomizes the core

17. So…if its an office building…
Alley
Easy Street
Adjacent
structure
High-value corner retail
Lower-value streetfront retail
Main Street

18. …but the tail can’t wag the dog
The corner retail will produce higher rental costs, but will it compromise the 15 floors of building above it?
The street-front retail will tolerate more spatial disruption due to its lower rents, but how much can we intrude on it?

19. Time to consider the cores
coreS?...not just one?
Every floor will need
Elevator access
2 means of egress (elevators won’t count)
Toilets for each gender
Some electrical/telecom space
Some space for ventilation/hvac
Could be a shaft
Could be a fan room

20. A midrise building core
men
elevators
mech
egress
egress
women
Will Paton, final study F2011

21. Basic organization forms
You might generate alternatives in more than one
Or the site, or inner organization of the clients enterprise might hint at which is most appropriate
Ultimately these begin to form a backbone, an armature to hang the building infrastructure upon.

22. Deploying infrastructure
Building planning is a design stage where the infrastructure elements of the building are located in ways that meet the appropriate codes and delineate space for the primary functions of the building

23. Put these somewhere…in a way that makes the primary functions better
Elevators
Stairways
Entry/Lobby
Toilets
Mechanical/Systems spaces
Circulation elements, corridors, egress paths

24. Know the land
From a building planning perspective, this might mean answering these questions
Where do we enter?
Where should trash and deliveries go?
Does the building have to be phased or planned for an addition?
Which orientation or orientations have the highest value? Which have the lowest?

25. Know a few things about the code
…how to get out in a fire
…how to arrange exits
…how big they have to be …

26. Egress
Promoter P.T. Barnum is said to have charged people 25 cents to enter a darkened room and “See the Egress.”
Once in the darkened room, the people could only see a dim light over a door with a sign on it saying “This way to the Egress.”
Upon opening the door and walking through they found themselves on the street!
Egress is the term applied to the various means (corridors, stair enclosures, stairs) to be used as a means of escape in the event of a fire or other disaster in the building.

27. Some key IBC Definitions
Area of Refuge: Area where persons unable to use stairways can remain temporarily to await instructions or assistance during emergencies
Corridor: An enclosed exit access component that defines and provides a path of egress travel to an exit.
Exit: That portion of a means of egress system which is separated from other interior spaces of a building by fire resistance rated construction and opening protectives as required to provide a protected path of egress travel between the exit access to the exit discharge including exit doors, exit enclosures, exit passageways

28. How Many People?
The IBC offers the choice of two processes for determining the number of people (occupants) in the building.
The first method is to determine the actual number of people in the space.
This is easier to do in a building with fixed seating (auditorium) than in say an open office space where, the density varies over time.
The second method is to refer to the Maximum Floor Area per Occupant table, find your use type, divide the number of gross square feet per occupant in the table into your project’s gross square footage to arrive at the number of occupants in the building, or per floor.

29. Occupant load table …excerpted
So our Business
Occupancy would take the program area (40,000 s.f.) and divide it by 100 s.f. to determine we have 400 occupants

30. Egress convergence
100
As the occupants from a floor above exit through lower floors, they don’t impact the exit size for the floor the pass through, but the exit size cannot get smaller.
But when exits converge at a floor, like the ground floor where they leave the building, the occupant load for the ground floor must take into account the occupant load of the floor immediately above.
First floor, 10,000 s.f. = 100 occ from second, 200 occupants
100
100

31. How wide does that make the exit?
The IBC reads “The total width of the means of egress in inches shall not be less than the total occupant load served multiplied by”
.3 for stairs in unsprinkled buildings
.2 for corridors, other egress components in unsprinkled buildings
.2 for stairs in sprinkled buildings
.15 for other components in sprinkled buildings
So our top floor stair in our unsprinkled example could be no less than 100 x .3 or 30 inches…not nearly wide enough to meet minimums of the IBC or ADA
So the code continues to read “nor less than specified elsewhere in this code” so it let’s itself out of an apparent contradiction

32. Stairways Two required
Fully enclosed with 2 hour fire rated construction
Minimum stair width 48”
Max stair width without intermediate railing = 5’ Minimum headroom 80” from nosing line
Max height between landings = 12’-0”
Max riser 7”
Min tread 11”
Within 3/8 of
same dimension for all steps
Minimum depth
Of Landing, 48”
Max intrusion of door on landing = 7”

33. Stairways…cont’d Handrail height 34” - 38”
Handrails required both sides. 1-1/4 to 2” dia, 1-1/2” from wall (clear)
Handrails must extend 12” beyond top riser, and one tread (11”min) beyond bottom tread
12”
11”

34. 2 exit spacing
Exits cannot be closer than 1/2 the maximum diagonal distance of the floor plate
80 feet
Diagonal is
100’ long so
1/2 diagonal is 50 feet
60 feet

35. 2 exit spacing
So in this example, the exit stairs could not be placed closer than 50 feet apart
Maximum travel distances would be for this type ‘B’ building
200 feet without sprinklers
250 feet with sprinklers
What would be the maximum stair spacing in a sprinkled type ‘B’ building?
So stair entries must be 50 feet apart, minimum
80 feet
50 feet
60 feet

36. Dead End Corridors
Dead End
20 feet
A corridor not ending in an exit is considered a dead end corridor
Dead end corridors are limited to 20 feet in length in most occupancies.
In occupancy group B with a sprinkled building, the dead end can be extended to 50 feet long.
Ends in an exit
Not a dead end

37. On your way to the exit...
DO NOT plan the egress path to exit through another tenants space
DO NOT plan the egress path to exit through storage spaces, kitchens, mechanical rooms…or other high hazard occupancies.
But exiting through a non hazardous accessory space is acceptable, as long as there is a clear path discernable to the exit.

38. Where do we enter? Prominence Number of entries Security Types Public
Employee
Service
Shipping/receiving

39. A 150x250 site
Alley
Easy Street
Adjacent
structure
Main Street

40. Zoning setbacks
Alley
Easy Street
Adjacent
structure
Main Street

41. Where do we enter? Alley Easy Street Possible Service Adjacent
structure
Possible Service
Barrier!
No view!
Possible employee entry
Best public/ employee entry
Main Street

42. Now you need the insight
If the employees have to clock in, change clothes, and report to the workspace, then the lockers/lunchroom/timeclock need to be near their entrypoint
If they just walk in and go to their workstation, there’s no need for this

43. Now you need the insight
If there is a public/retail first floor, the street-fronts become high value, so putting employee or utility functions there would be counterproductive
If the business ships and receives high volumes of product, then the side-street and alley become high value.
Regardless, we need to keep in mind, trash storage, backup generators, and misc. delivery

44. Example, multi-tenant office bulding
Key issues
Return on investment
High net to gross ratio (what’s that?)
Clear circulation/wayfinding
Maximize value of perimeter glass/views
Allow for street level retail

45. Public/employee sequence dominates…but doesn’t locate
elevators
Lobby/Reception/directory/security
retail
retail
Double loaded lobby allows two retail tenants
Single loaded would allow one larger tenant
Challenge might be identity
Entry/vestibule

46. If its an office building…
Alley
Easy Street
Adjacent
structure
High-value corner retail
Lower-value streetfront retail
Main Street

47. …but the tail can’t wag the dog
The corner retail will produce higher rental costs, but will it compromise the 15 floors of building above it?
The street-front retail will tolerate more spatial disruption due to its lower rents, but how much can we intrude on it?

48. Time to consider the cores
coreS?...not just one?
Every floor will need
Elevator access
2 means of egress (elevators won’t count)
Toilets for each gender
Some electrical/telecom space
Some space for ventilation/hvac
Could be a shaft
Could be a fan room

49. A midrise building core
men
elevators
mech
egress
egress
women
Will Paton, final study F2011

50. A minimal stair 48 inches between handrails
1.5” handrails (each side) that are 1.5” from the walls
So a single run of stairs is 54” wide
If the stair runs between 12 foot floors,
12x12=144” of rise
divided by max riser 7.0 = 20.5 risers, say 21 at 6.8” or just over 6 and ¾ inches.
always one less tread than riser so 20 risers at min dimension of 11 inches so 20x11inches = 220 inches or 18 feet 4 inches of horizontal run, add 6-5 foot landings at the top and bottom if doors open into the stairs) (and, not counting the ARA), the overall inside of the straight run stair is 31’2” x 5’4” wide.
now work out a dual run stair.

51. Building Planning… Part II
Core strategies

52. Other core responsibilities
Besides housing egress, access, toilets and HVAC, cores often act as the primary space definition elements on a floor.
They also are often used for lateral bracing of the structural frame, with walls reinforced to be shear diaphragms or with “X” bracing or chevron bracing concealed within their enclosing walls

53. Core location

54. Core location

55. Lever House, NYC,
Gordon Bunshaft, 1952

56. Core location

57. Sendai Mediateque, Ito atomizes the core

59. Considering cores… Alley Easy Street Adjacent structure
High-value corner retail
Lower-value streetfront retail
Main Street

60. A minimal stair 48 inches between handrails
1.5” handrails (each side) that are 1.5” from the walls
So a single run of stairs is 54” wide
If the stair runs between 12 foot floors,
12x12=144” of rise
divided by max riser 7.0 = 20.5 risers, say 21 at 6.8” or just over 6 and ¾ inches.
always one less tread than riser so 20 risers at min dimension of 11 inches so 20x11inches = 220 inches or 18 feet 4 inches of horizontal run, add 6-5 foot landings at the top and bottom if doors open into the stairs) (and, not counting the ARA), the overall inside of the straight run stair is 31’2” x 5’4” wide.

61. Stairways Two required
Fully enclosed with 2 hour fire rated construction
Minimum stair width 48”
Max stair width without intermediate railing = 5’ Minimum headroom 80” from nosing line
Max height between landings = 12’-0”
Max riser 7”
Min tread 11”
Within 3/8 of
same dimension for all steps
Minimum depth
Of Landing, 48”
Max intrusion of door on landing = 7”

62. Stairways…cont’d Handrail height 34” - 38”
Handrails required both sides. 1-1/4 to 2” dia, 1-1/2” from wall (clear)
Handrails must extend 12” beyond top riser, and one tread (11”min) beyond bottom tread
12”
11”

63. Other core responsibilities
Besides housing egress, access, toilets and HVAC, cores often act as the primary space definition elements on a floor.
They also are often used for lateral bracing of the structural frame, with walls reinforced to be shear diaphragms or with “X” bracing or chevron bracing concealed within their enclosing walls

64. Considering cores… Alley Easy Street Adjacent structure
High-value corner retail
Lower-value streetfront retail
Main Street

65. Chicken or the egg?
What sets the core-to-skin distance?

66. How far is it from the core to the skin?

67. Know your typology…what’s that mean?

68. typology meets client culture…meets market…

69. Client Culture, Organization, and Form

70. Market needs inform

73. Modularity…common denominators…
Planning grids
Structural grids
Lighting grids
Power grids
Mechanical grids

74. Built from the most common…and smallest acceptable unit of space

77. 10’
Minimum skin to core?
14’ 6’
10’

78. 10’
10’
10’
Minimum structural?
14’ 6’
10’

79. Check structural capability
Steel Frame
Cast-in-Place Concrete Frame
Precast Frame

80. Steel R.O.T. p.356 Depth of Girders = 1/15 span
(width=1/3 to 1/2 depth)
Depth of Beams 1/20 span
(depth of slab included in composite structures)
Depth of bar joists 1/20 span
(spacing 2 to 10 feet depending on decking / concrete thickness)
Depth of decking and concrete for floors 1/24th of span (2 1/2 to 7 inches typical)
Depth of decking for roof 1/40 th of span (1 to 4 inch decking available)

81. Bay proportions…are long girders better?
20’
Here the girders are spanning 40’ and are framing into the columns and carry the secondary floor beams.
This requires
W30x108 girders
And
W16x26 beams
With a 5 1/4” slab over the beams
that’s 6,400 pounds of steel in this bay
40’
16”
30”
14” for ductwork, lights...

82. Site-Cast-Concrete Systems…Basic flavors
Basically, there are 4 types of slabs an architect chooses from when considering a system for a project.
Slabs are usually flat, can be reinforced to span one way or two ways. Their span usually depends on their depth, but there is a point where the extra concrete in the depth works against the slab due to its weight.
Joist slabs usually can span farther and carry heavier loads because they eliminate concrete not contributing to the slabs strength. (hence the joists)
All diagrams from Allen “Architects Studio Companion”

83. One way flat slabs…will it work?
The one way slab spans between beams or columns. It requires a structural bay (spacing between columns in both directions) that is within 20% of being square.
It is usually used for light loading applications where it’s thin structural depth gives a low floor to floor height.
When heavily loaded it requires the beams below the slab, It is more desirable to NOT have these beams as they take additional labor to form and pour.
Costs
25x25 6” 40psf load about $13.80 per sq.ft.
25x25 6” 125psf load about $17.20 per sq.ft.
Span min 6’
Span max 18’
R.O.T. Slab depth 1/22th of span
Postten rot Slab depth 1/40th of span
Min thick for 2hr = 5”
Min thick for 3hr = 6 1/2”

84. One way joist slabs
Joist
Slab
Joist band (beam)
void
To address heavier loading conditions, its necessary to remove the concrete that’s acting as dead weight - working against the slab that comes along with an increase in the uniform thickness of a slab.
This one way joist slab does just that, using prefab formwork set on a plywood deck voids are formed between the joists which make the slab lighter, and stiffer.
The joists bear into beams (called bands) spanning from column to column. These bands give this system the ability to move columns off the grid, (as long as they still fall under the bands) allowing for more plan flexibility.
Costs
25x25 12” 40psf load about $14.10 per sq.ft.
25x25 12” 125psf load about $16.50 per sq.ft.
Span min 12’
Span max 45’
R.O.T. Slab depth 1/18th of span
Postten rot Slab depth 1/36th of span
Min thick for 2hr = 5”
Min thick for 3hr = 6 1/2”

85. Standard Spanning elements
Solid slabs
Hollow core slabs
Double tees
Rectangular beam
“L” beams
“T” beams

86. Each piece is numbered for location according to the shop drawings.
This producer also dates each piece to be certain only fully cured components are installed
Castellated joint

87. Hollow Core slabs
Like sitecast slabs, when the depth of a solid slab increases past a certain point, the extra weight of the concrete works against the spanning member.
In precast, the hollow core slab, removes unemployed concrete increasing the structural efficiency of the slab.
Unlike the solid slab, the hollow core slab is reinforced with prestressing strands in the top and bottom of the slab.

88. Spanning
The hollows are made in different ways by different companies. Some have expanding air cylinders, some use pea gravel laid in the bottom half of the pour.
Span max 45’
Widths 2’-0”, 3’-4”, 4’-0”, 8’-0”
Span / Depth ratio 1/40
Min produced depth 6” (2” increments)
Max produced depth 12”
Cost per s.f. topped $12.50
Cost per s.f. untopped $10.50

89. aka the plank
Like the solid slab, the hollow core slab (also known as the hollow core plank) has castellated joints to form shear keys when filled with grout.
This helps the planks work together and increases structural efficiency.
Like other precast systems when used as floors, the hollow core plank needs a topping slab (2” or so) to level out the camber differences, make a diaphragm for lateral resistance, and make a place for electrical and hot water heating utilities.

90. Long beams, short planks or long planks short beams?
20’
Long beams, short planks or long planks short beams?
One way 8”
3’-4”
2’-8”
40’

91. 40’
20’
The longer a beam spans, the deeper it must be. While the plank stays pretty much the same. (the number of prestensioned strands increases)
In this example, say the beam span is 20 feet, the rule of thumb of d=1/15 s gives 20/15=1’-4” deep. The plank spans 40 feet here and which gives an 12” plank. This makes a 2’-4” deep structural sandwich

92. 40’
20’
That’s a FOOT thinner! In a 8 story building it gives the owner an extra floor for FREE!
So bay size has a LOT to do with structural depth, which has a significant impact on the projects economics!
12”
2’-4”
1’-4”

93. Beams & floor to floor heights…look familiar?
Supporting the spanning member on top of the beam adds to the floor to floor height, but, if the spanning member on top of the beam is a single or double tee, the space between the top flange and bottom of the stem is available for ductwork to pass over the beam with no conflict!
Duct
Duct
Space!

94. Mechanical Planning Is mostly about providing ventilation …and cooling
…with big…noisy…machines
You can choose to Centralize or Decentralize the air handling machinery in the building
Mechanical Planning
Hybrid
Centralized:
Big vert shafts
Decentralized:
Mech rooms each floor

95. If Shafts…plan for trunks
Trunk ducts are the main ducts that emerge from the shafts
Since they serve large areas of floorspace, they contain lots of air and are bigger than distribution ducts
Don’t trap shafts behind elevators and stairs

96. If Shafts…plan for trunks
Plan return ducts to run inboard of supply…supply has to be delivered to the building skin, returns can be interior

97. Structure & trunk ducts
Short span
Plan a short structural span next to the core if possible, it makes for a thinner structural section to allow trunk ducts to pass
long span

98. Put it all together… Seeking modularity
You’re looking for the common denominators
Is the smallest space an increment of the largest?
Will the smallest plus a circulation path be modular with the most frequently found space increment?
Is the structure an increment of the smallest and largest spaces?
Remember..
Grids don’t need to be uniform
Core functions can be environmental buffers
Smaller grids spacing makes for shallower structure, very helpful if coordinated with maximum ductwork depth
Mechanical zones are usually functional, environmental or some combination of the two.
Ductwork is best run over circulation spaces, it gives better acoustic isolation.