According to their position, stairs are categorized as follows:
Interior
Exterior

According to their function, they are categorized as follows:
Main stairs
Service stairs
Portable stairs

According to their construction, stairs are categorized as follows:
Stone stairs
Timber stairs
Concrete stairs
Iron and steel stairs
Stairs from modern materials

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Stairs are classified according to their plan form as follows:
Straight stairs: they stretch from a lower to an upper level in one straight run
Return (U) stairs: with two flights of steps parallel to each other with a landing between
Circular stairs: they sweep in a broad curve from one level to another
L stairs, double L stairs: they make a 90-degree turn at a landing
Winder stairs: they have “pie-shaped” steps which substitute a landing
Spiral stairs: they generally have winder steps and they twist around a centre pole

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Prime considerations in stair design should be easy use and safety. The available space will make us determine the stair’s shape.

Straight stairs are easy and not expensive to construct, but they require plenty of space.

That’s why stairs with a landing (L-shaped or U-shaped stairs) are often preferred if there’s enough space for them. Winder stairs are used when the space is not sufficient for the L stairs.

Spiral stairs

are used where little space is available. They are not very safe and they are also hard to climb.

The wider and gradual the stair, the more space it will consume.

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Stair Terminology

Tread: the horizontal surface for the foot to ascend from one level to another

Riser: the vertical distance between the upper surfaces of two consecutive treads

Flight: a series of steps between floors or landings

Landing:  a platform between two flights that either acts as a resting place, a change of direction or is the end of the stair

Nosing: the front edge of the tread that hangs over the riser

Going:  the horizontal distance between nosings

Stringer: the angled beam or member at each side of the stair that supports the treads

Balustrade: A railing system which provides protection on the open sides of a stair

Total Rise: the total vertical distance from floor to floor

Total run: the length of all of the treads combined

Pitch: the angle that the flight of stairs is built at

Headroom: the distance from the leading edge of a tread to the header directly above

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Constructing to Current Building Regulations

All new staircases designed and installed in the UK must meet the standards and guidelines set by the ‘Approved Document K – Protection from falling, collision and impact’ Sub-sections K1 to K5. Part ‘K’ has been developed to make sure staircases are designed safely and covers additional items such as guides to riser heights, tread widths, handrail heights, workmanship, health and safety, head heights limits.