07 stair

STAIR DESIGN & CONSTRUCTION

ID 270 – BUILDING SYSTEMS & MATERIALS

STAIR DESIGN

Stair Components:

•  Tread •  Riser •  Stringer •  Rise / run •  Handrail •  Balustrade •  Nosing •  Winder •  Newel post

STAIR DESIGN

Commercial v. Residential Stairs: •  Egress stairs (protected path) must be enclosed and be made of fire-rated . materials as per code •  Non-egress stairs may be open and are not subject to the same fire codes

•  Minimum head clearance in residential buildings is 6’-6” •  Minimum head clearance in commercial buildings is 6’-8”

•  Minimum width in residential buildings (or occupant load < 50) is 36” •  Minimum width in commercial buildings with occupant load > 50 is 44”

•  Maximum handrail profile encroachment in commercial buildings is 4½” into . minimum width •  Maximum handrail profile encroachment in residential is 3½” into minimum width

•  Caveat: codes vary for all circumstances; must verify dimensions accordingly!

STAIR DESIGN

Stair Drawings: Clearances and Dimensions

STAIR DESIGN

Commercial v. Residential Stairs: •  Egress stairs (protected path) must be enclosed and be made of fire-rated . materials as per code •  Non-egress stairs may be open and are not subject to the same fire codes

•  Minimum head clearance in residential buildings is 6’-6” •  Minimum head clearance in commercial buildings is 6’-8”

•  Minimum width in residential buildings (or occupant load < 50) is 36” •  Minimum width in commercial buildings with occupant load > 50 is 44”

•  Maximum handrail profile encroachment in commercial buildings is 4½” into . minimum width •  Maximum handrail profile encroachment in residential is 3½” into minimum width

•  Caveat: codes vary for all circumstances; must verify dimensions accordingly!

STAIR DESIGN

Stair Drawings: Handrails

STAIR DESIGN

Handrails and Railings:

•  Handrails on both sides of a stair required in commercial buildings

•  Handrails required only on one side in private dwellings

•  Handrail gripping surface must be continuous and without obstructions

•  In residences, newel posts are allowed at landing and at base of stair

•  Extra-wide egress stairs must have intermediate handrails, within 30” of reach

•  Handrails must be located at 34”- 38” above nosing (generally required at 36”)

•  End of handrail must have a return

•  Handrails in public buildings must extend at both the top and bottom of a flight of stairs

•  Inside railing at switchback stairs must be continuous (change in slope)

•  Railings and balustrade members must have no gaps 4” or larger

•  Balustrades should be oriented vertically so as not to encourage climbing

STAIR DESIGN

Stair Drawings: Plan and Section

STAIR DESIGN

Stair Drawings: Handrails

STAIR DESIGN

Treads and Risers: •  Treads must be at least 10” deep (not including nosing) in residential buildings •  Treads must be at least 11” deep in commercial buildings and in compliance with ADA •  Must be strong enough not to deflect under span, weight, and concentrated force

•  Risers must be no greater than 7¾” in residences •  Risers must be no greater than 7” in commercial buildings •  Open risers are generally not allowed by code •  Difference in riser height permissible < 1/8”per riser, or 3/8” over length of run

•  Nosings cannot project more than 1½”and have a maximum radius of ½”

•  Number of treads in a straight run stair is 1 less than the number of risers, and 2 less in a switchback (landing instead of tread)

•  Proportion of tread depth to riser height: 2R + T = 25” (most comfortable for stride)

STAIR DESIGN

Stair Drawings: Nosing Profiles

STAIR DESIGN

Stringers:

•  Open stringers (treads fastened from above)

•  Closed stringers (treads fastened from side)

•  Code requires (3) 2 x 12’s for 36” wide residential stair

•  Kicker plate at bottom to anchor stair structure

•  Mounted at top with hangers or plates onto floor structure

•  May be exposed or finished with fire-rated gypboard + sound insulation

STAIR DESIGN

Stair Drawings: Stringers

STAIR DESIGN

Spiral Stairs: •  Head clearance of 78” •  Riser height may not exceed 9½” in non-egress conditions •  May be used as means of egress if exit access space is < 250 sf and < 5 occupants •  Same riser heights as per code apply for egress •  Minimum diameter for egress = 5’- 0”; 26” clear width + 4” center column (steel) •  Can make three-quarter turn or full 360 degree turn •  One baluster per tread •  Center column (cantilever) OR Center column + stringer OR Double stringer

STAIR DESIGN

Stair Drawings: Spiral

STAIR DESIGN Fire Egress Stairs: •  Must be completely enclosed •  Must be made of fire-rated materials (fire-rating according to code) •  Generally made of concrete in public buildings requiring egress •  Width dimensions depend on occupancy load •  Rescue assistance requirements to accommodate rescue personnel and waiting . areas on landings for wheelchairs •  Number and locations of fire stairs regulated by code •  Minimum distance between stairwells in large commercial building is 30 ft

STAIR DESIGN

Stair Types: Straight Run

If rise > 12’, then landing required

STAIR DESIGN

Stair Types: L-shaped & Winders

STAIR DESIGN

Stair Types: Switchback or Return

STAIR DESIGN

Stair Types: Curved and Spiral

STAIR DESIGN

Stair Types: Other Shapes

STAIR DESIGN

Stair Types: Alternating

STAIR DESIGN

Stair Types: Sculptural Stairs

STAIR DESIGN

Stair Types: Heightened experience

STAIR DESIGN

Stair Types: Sculptural Stair Details

STAIR DESIGN

Stair Materials: glass, steel, wood, concrete

STAIR DESIGN

Decorative Stairs: lighting, color, images, motif

STAIR DESIGN

Decorative Railings:

STAIR DESIGN

Stair Drawings: Residential Stair details

STAIR DESIGN

Stair Drawings: Commercial Stair details

STAIR DESIGN

How to calculate stair dimensions:

•  Start with determining riser dimension because floor height is fixed (treads and . horizontal run have more flexibility)

•  Calculate the floor-to-floor height (ceiling height + floor thickness, including finish . floor); convert to inches

•  Divide by a standard 7” riser height

•  For commercial buildings, round up, and for dwellings, round down; this represents . the number of risers

•  Divide the floor-to-floor height by the number of risers to establish the exact riser . height, and verify that the dimension meets the applicable code

•  Number of treads is 1 less for straight run, and 2 less for stair with landing

•  Depth of tread can be calculated by available run, code requirements, and tread/riser . proportion

STAIR DESIGN


•  Calculate the floor-to-floor height Ceiling height = 8’– 0” = 96” Floor thickness = 2 x12 + gypboard ceiling + subfloor + finish floor

= 11-1/4” + 5/8” + 3/4“ + 3/4” = 13-3/8” Ceiling height (96”) + floor thickness (13-3/8”) = 109.375”

Determine riser:

•  Divide by a standard 7” riser height = 15.625 For commercial buildings, round up = 16 risers For dwellings, round down = 15 risers

•  Divide the FTF height by the number of risers (verify with code) Commercial = 6.836” Residential = 7.29”

STAIR DESIGN


Determine tread & run:

•  Straight run commercial stair will have 15 treads

T = 25 – 2R (13.67) = 11.33”; run = 11.33” x 15 treads = 170” (14’– 2”) Minimum run = 11” x 15 treads = 165” = 13’– 9”

•  Straight run residential stair will have 14 treads T = 25 – 2R (14.58) = 10.42”; run = 10.42” x 14 treads = 145.88” (12’–1-7/8”) Minimum run = 10” x 14 treads = 140” = 11’– 8”

STAIR DESIGN How to draw stairs: By hand:

•  Use architectural scale and set 0 to 1st floor and 15 (# of residential risers) to 2nd floor

•  Draw a diagonal line (this represents the slope of your stair) and tick off every foot

•  Draw horizontal construction lines through each tick; these represent your treads

•  Draw vertical line from tick to construction line below; these represent your risers

In AutoCAD:

•  Draw a vertical line from first to second floor

•  Use your ‘divide’ command to divide into 15 parts

•  Snap horizontal construction lines through each tick to establish your tread locations

•  Set vertical line for either top or bottom tread (depending which point is fixed)

•  Offset by your tread dimension (10.42” for residential) to establish your riser locations

STAIR DESIGN

Exercise: Calculate stair dimensions for the community center

07 stair

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