8/10/2019 8 Stairs.pdf

1/6

50

STAIRCASE

8/10/2019 8 Stairs.pdf

2/6

51

TerminologyStep: The step is composed of the tread and riser.

Tread: The part of the stairway which is stepped on.

Riser: The vertical portion between each tread on the stair.

Nosing: An edge part of the tread that protrudes over the riser beneath.

Bullnose: Where stairs are open on one or both sides, the first step above the lower

floor may be

wider than the other steps and rounded.

Stringer: The structural member that supports the treads and rises.

Winders: Winders are steps that are narrower on one side than the other. They are

used to change the direction of the stairs without landings.

Trim: Normally applied where walls meet floors and often underneath treads to hide the

reveal where the tread and riser meet/

Handrail: The angled member for handh olding, as distinguished from the vertical

balusters which hold it up for stairs that are open on one side.

Guardrail: Required to protect the open glazed sides of stairways, ramps, porches, and

unenclosed floor and roof openings.

Gooseneck: The vertical handrail that joins a stopped handrail to a higher handrail on

the balcony or landing.

Landing: A platform between flights of the stairs or at the termination of a flight of stairs.

Stairs are important links in an overall circulation scheme of a building as it provide

means for moving from one level to another. Whether interjecting a two-story volume or

rising through a narrow shaft, a stairway takes up a sign ificant space. The most

important considerations in the design and placement of stairs are the safety and its

ease of travel. To preven t overly complicated framing condi tions at the later stages of

construction, the landings of a stairway shou ld be logically integrated with the structural

system.

SUPERSTRUCTURE

STAIRS

BYJIILIANGOHJOONJIN

8/10/2019 8 Stairs.pdf

3/6

52

Types of Stair Plans

Straight-Run Stair

- A straight-run stair extends from

one level to another, absence of

turns or winders

- Building codes generally limit the

vertical rise between landings to12 (3660).

Quarter-Turn Stair

- A quarter-turn or L-shaped stair

makes a right angled turn in the path

of travel

- The two flights connected by anintervening landing may be equal or

unequal, depending on the desired

proportion of the stairway openin g

Half-Turn Stair

- A half-turn stair turns 180or

through two right-angles at the

intervening landing

- A half-turn stair is more compact

than a single straight-run stair

- The two fights connected by the

landing may be equal or u nequal,

depending on the desired

proportion of the stairway openin g.

Winding Stair

- A windin g stair is any stairway

constructed with w inders, as a circular

or spiral stair.

- Winders can be hazardous since theyoffer little foothold at their interior

corners. Building codes generally

restrict the use of winders to private

stairs within individual dwelling units.

Pic 1 shows an example of half -turn stair

at the construction site.

Pic 2 shows a fin ished winding stair at thesemi-detached house.

Pic1Pic2

8/10/2019 8 Stairs.pdf

4/6

53

In-Situ Reinforced Concrete Stairs (Construction method)

Formwork may vary for different types of reinforced stairs but the basic principles do still apply for all. Timber formwork is observed in the construction site.

The solid wooden boards must be load bearing to support the weight of the concrete.

Several fixtures are used to join and fasten the riser boards to the lateral structure of the formwork. The reinforcement bars (joist) are installed in the

formwork.

Simple reinforced concrete steps is based on the following requirements:

- concrete mix of M15 (1:2:4) / 20mm aggregate

- minimum cover to reinforcement 15mm or bar diameter or greater value for 1 hour fire resistance

8/10/2019 8 Stairs.pdf

5/6

54

Measurements

The rise height orrise of each step is measured from the top of the first tread to the next.

The tread depth of a step is measured from the edge of the nosing to the vertical riser.

The going of a step is measured from the edge of the nosing to the edge of nosing in plan view.

The total run ortotal going of the stairs is the horizontal distance from the first riser to the lastriser.

Total Run = (No. Risers - 1) x Unit Run

The total rise of the stairs is the height between floors (or landings) that the flight of stairs is

spann ing. If there are Nsteps, the total rise equals Ntimes the rise of each step.

The slope orpitch of the stairs is the ratio between the rise an d the going (not the tread depth,

due to the nosing).

Headroom is the heigh t above the nosing of a tread to the ceiling above it.

There are many types of materials use in stairs construction .

Wood

They have poor resistance to fire and only used for small residential buildings. They are light-weight and the

timber used shou ld be free from fungal decay or insect attack. The wood should be well treated before use.

In-Situ Reinforced Concrete (Pic 2))

It is usually designed as an inclined, one way reinforced slab with steps formed on its upper surface. It acts

as a simple beam if the stair is constructed after the floor beam or wal l supports. If it is cast with the beamor slab supports, it is designed as a continuous beam. Concrete stairs require careful analysis of load,

span, and support conditions.

Steel

Pre-engineered and prefabricated steel stairs are available. They require regular maintenance in the form of

painting to protect from corrosion. Mostly used for spiral stairs and made up of mild steel or cast iron.

In-situ reinforced Concrete

Pic1

Pic2

8/10/2019 8 Stairs.pdf

6/6

55

an ar equ remen s:Stairway design is strictly regulated by the bui lding code. Thedimensions of the stairway are subjected to the requirements approvedby the Department of Standards Malaysia.

Risers and Treads

- Tread depth: 11 (280) minimum- Riser height: 4 (100) minimum; 7 (180) maximum

- Uniform riser and tread dimensions are required to prevent slipping- More than 16 risers per fligh t are not encouraged

- Open risers are not permitted

Stairway Width- The occupant load determines the required width of an exit stairway.- 44 (1120) minimum clear width; 36 (915) minimum for stairways

serving an occupant load of 49 or less

Landings- Landings should be at least as wide as the stairway width and have

minimal length of 44 (1120) measured in the direction of travel.Landings in dwell ing units may have a minimum length of 36 (915).- When door is ful ly open, the door must not intrude into required widthby more than 7 (180).

Handrails

- Required on both sides of the stair. The building code allowsexceptions for stairs in individual dwelling units, stairways less than 44(1120) wide and stairs having less than fou r risers.- 34 to 38 (865 to 965) height above the leading edge of the stairtreads or nosings.

- Should be continuous without any obstruction- One handrail shou ld extend at least 12 (305) plus one tread widthbeyond the bottom riser. The ends shou ld return smoothly to a wall orwalking surface, or continue to the handrail of an adjacent stair flight.

Detailed Analysis- The stairs have full landing- Closed risers- Absence of skirting- Treads width meets the standard requirements.

- Risers height meets the standard requirements.- Landings and stairs have equal width- Single handrail as permitted in dwelling units

If there is a door at the landing, the door should swing in the directionof egress and door swing must not reduce the landing to less than onehalf of its required width. - When door is fu lly open, the door must notintrude into required width by more than 7 (180).