INTERNAL STAIRS AND HANDRAILS Construction Systems 1.

INTERNAL STAIRS AND HANDRAILS

Construction Systems 1

Learning Objectives…

© Unitec New Zealand

Students will be able to demonstrate their knowledge of this topic by: Describing components, assembly, installation, material selection, and finish of internal stairs and handrails Describing the different systems used in stair design Describing assembly, fixing and finishing of internal stairs in compliance with NZBC clause D1 Access Routes and F4 Safety from Falling Unit Standard 9671: Element 6: Determine and describe the methods used to construct the interior of a small building.

The Humble Stair…..

We love to sit on stairs and often meet on stairs then stop and talk.

In the movies people like to fight on the stairs .

Often seen as a link between heaven and earth.

Stairs- functional requirements…..

NZBC D1 Access Routes has specific provisions relating to the performance requirements of stairs and these include:

1. Provision of adequate footing and slip resistance to treads for all use conditions.

2. Prevention of children falling through, or becoming wedged between open treads.

3. Having a uniform rise and tread within each flight and for consecutive flights.

4. Not having isolated or single steps.5. Having smooth, reachable, and graspable

handrails complying with strength requirements.6. Providing the correct number of, and correctly

sized, landings7. Leading edges of treads being readily identifiable.8. Correct pitch (stair steepness) for the activity or

location

All the above factors are related to safety, but others that could also be addressed are concerned with aspects such as design and aesthetics

Stairs- everybody uses them , but what in basic terms are they required to achieve ?

Have handrails and balustrades that are not “ easily climbable “

Be adequate for use as a means of escape in Fire.

Be suitable for use by firefighters.

Be of an artistic or unique design using specific materials.

Match existing stairs in a conservation project .

Provide other facility such as storage area underneath.

Be within a certain budget that the client can afford.

Capable of use by people less able or ambulant than normal, or with sight impairment.

Of sufficient size to enable furniture to be provided in the rooms that the stair serves.

Be of a durable design and construction to avoid excessive deflection and not generate noises and creaks

Additional factors and criteria that a stair design solution may have to satisfy.

Stairs- functional requirements

Buildings in central Amsterdam have very narrow and steep stairs because of narrow section sizes . Furniture was lifted up using external lifting beams which are a feature of the older houses.

Even modern homes though have stairs that would not comply in other countries.


Easily climbable – what kids of 4-6 can actually get over may surprise you.

As a result some handrail or balustrade designs will not comply


Stairs as art and storage. Which is a functional requirement?

Can the stairs satisfy these possible client requests and still comply?


What information would the designer need or get from a client brief that would influence and help determine his stair design proposal ?

Stairs- Design Criteria

Private Stair - a stairway used, or intended to be used by the occupants of a single household unit

Service Stair - a stairway that is used infrequently by service personnel to gain access to spaces for the purpose of maintenance and the movement of goods.

Common Stair - a stairway used by the public.

Accessible Stair - is one which has features to permit the use of the stairs by people with disabilities.

Main Private Stair - intended to provide access to and between frequently used spaces such as living areas, kitchens, and garages and includes all exterior private stairways.

Minor Private Stair - a private stairway not on a main thoroughfare, and intended to provide infrequent access to a single room which is not a living area or kitchen.

Secondary Private Stair - a private stair other than a main or minor private stair intended to provide access to another floor containing only bedrooms, bathrooms or similar accommodation.

Stair Types:

Stair terms and definitions….

Overview of typical staircase and basic elements.

Balustrade - a combination of balusters and handrail Newel Post- the substantial vertical member placed at ends of flights to support the strings and handrails

Pitch - the angle between a line that connects the front face of the tread/nosing (parallel with the stringer) and the floor

Going - the horizontal distance from face to face of consecutive risers. Tread less any nosing (ie the plan view of the tread). Total going is the horizontal distance from the face of the first riser to the face of the last riser. Rise - the vertical distance between two consecutive stair treads. The total rise is the vertical distance from the top of one floor to the top of the floor above. Step - the tread and riser combined String/Stringer - the inclined member supporting the treads

Stair terms and definitions…..

Flight - a series of steps without a landing

Tread - the horizontal upper surface of the step on which the foot is placed

Riser - the vertical member of the step used to connect the treads together

Nosing - the length of the tread projecting over the lower tread


Landing - a level platform at the top of a flight of stairs Handrail - a rail fixed parallel to the string Balusters - short vertical bars that support the handrail and protect the open side of the stair. The baluster may be replaced by a solid balustrade.


Head height and clearance….

Diagram showing clearance required over access routes taken from D1-NZBC. Inadequate headroom can result in unsafe conditions because the stairs users attention is focussed on head clearance while it ought to be concentrated on the stair nosings. Headroom should be at least 2m measured vertically from the pitch line.Requirements similar to other countries such as UK regulation shown below.

Stair pitch…..

Pitch - the angle between a line that connects the front face of the tread /nosing (parallel with the stringer) and the floor.

As can be seen on the right, there are limits to the pitch that can be used in the stair dsign.

This will depend on the context , building type, where the stair is located and also the rooms which it serves.

Stair pitch….

Table from D1 showing design limits for stair pitch and other elements.

Stair DesignWider rather than narrower tread depths provide increased safety during the descent. Stairs with a pitch of less than 23 degrees do not permit people with normal gait to use them comfortably. Riser and tread dimensions must be uniform throughout the same flight of stairs. Treads must not project past the riser by less than 15mm or more than 25mm for open stairs or by more than 25mm for stairs with closed risers. The number of risers in a flight should not exceed 17 Where does this come from see table 7 below (without a landing) with 14 – 16 a desirable number for able-bodied users.

Acceptable for all stair types

Desirable 23 – 37 deg.

0-25mm allowable

Result – note: allowable in all stair types

Stair Design

Doors must open away from stairs and must never open directly onto a flight – there must be a landing between the door and the stairs.

Space beyond door swings provided on landings.

Stair Design

The height of the riser is normally determined by the floor to floor height of the building and the rule of thumb for a common or main private stair is to have a rise of between 170 and 190mm and a tread of 275 to 300mm (max pitch of 37 degrees).

Pitch limits for different stair types.

Stair Design; details…..

Handrails perform a lot of functions including : drawing the users attention to the stair and making them aware of a potential hazard, providing an easily reached point for support if the user stumbles and provides a continuous support for people who may have problems negotiating the stairs. Handrail heights vary, but should be between 900 and 1000mm from the pitch line. (930mm appears to be the optimum for safety purposes)

Stair Design; handrails….

Stair Design; handrails….

A handrail must provide a comfortable and safe handhold. Circular or oval shapes having a relevant width of between 20 – 80mmØ (35 - 50mm appears to provide the best grip). A 45-60mm clearance must be provided between the wall and handrail.

Stair Design; balustrades..

Stairs that are not enclosed by walls on two sides require balustrades. Balustrades must be a minimum height of 900mm (above the pitch line) on stairs. Designed to comply with the requirements of NZBC F4 Safety from Falling. In any buildings likely to be used by children, balustrades must not have gaps through which a 100mm diameter sphere can pass. No components which can provide a toehold must be installed between the heights of 150mm and 760mm. In addition, any triangular – shaped opening between the balustrade and stair tread must be small enough to prevent a 150mm diameter sphere passing through.

Barriers; windows…

> 1.0m

Housing and buildings likely to be frequented by small children

Restrictor, or..

>760mm, or..

760 mm Barrier

Stair design; defects…

Accidents -Studies have shown that more accidents occur when users are going down stairs due to over stepping the tread. Wider rather than narrower tread depths provide increased safety during the descent. Stairs with a pitch of less than 23 degrees do not permit people with normal gait to use them comfortably. Riser and tread dimensions must be uniform throughout the same flight of stairs. Treads must not project past the riser by less than 15mm or more than 25mm for open stairs or by more than 25mm for stairs with closed risers. The number of risers in a flight should not exceed 17 with 14 – 16 a desirable number for able-bodied users.

Accidents- Implications for accidents and injuries can be serious.

If the stairs don’t comply, who is liable when someone gets injured ?

Stair design; defects…

Accidents on stairs….

Accidents usually occur going down stairs.

On the right is a list of common defects that lawyers may check for !!

© Unitec New Zealand 29

Stair design defects…

There are lots of questions that will have to be answered in the event of an accident on stairs and many will involve the design !

>>FACULTY OF TECHNOLOGY AND BUILT ENVIRONMENT

Stair ConstructionThere are many different construction methods for both internal and external stairs and the designers approach will consider the architectural style of the house, the location of the stair itself, appropriate materials and cost implications, and the geometry of the stair design

Construction varies from standard techniques based on traditional design to one-off job specific construction.


Stair ConstructionWide variety of materials available but many residential and traditional stairs were fabricated from Timber. High levels of skill and workmanship required.


Stair Construction

Typical timber stair section.

Timber stair during construction.


Stair ConstructionTimber stair under construction


Stair Construction- BIM model with Archicad

Stair modelled up in Archicad for client approval and fabrication.


From virtual to reality. Designers can use CAD packages to help design individual stairs.

Stair Construction- BIM model with Archicad


One off stair in steel and glass following specific client instructions.

Stair Construction

Ref: NZBC: D1

Statutory Documents

Regulations and guidance which stair designers have to follow.


Space saving design , but would treads comply ?


Stair design examples: Do they Comply with the NZBC?

Space saving dual function stair , but does it comply ?


Space saving design, but would treads comply ?

Folded steel plate treads and risers

Stairs as storage

Stair design examples..






Stair by Michaelangelo.





Stairs by Thomas Heatherwick.

Complying with the building code is about safety it doesn’t have to inhibit design…


Space saving design, but would treads comply ?







Stair by Gunnar Asplund at Stockholm Town Hall



Stairs by Carlo Scarpa


© Unitec New Zealand 48Carlo Scarpa

Stairs in Venice by Carlo Scarpa.


50© Unitec New Zealand

1. What is the minimum width between balusters/pickets in a barrier?

2. When are windows required to function as a barrier to prevent people from falling?

3. What can be used to protect window openers?

4. When can spiral stairs be used?

5. When are open risers permitted?

6. What is the minimum tread depth of an accessible stair?

7. Name two reasons that landings might be required?

8. How many handrails are required on an accessible stair 1.2m wide?

9. How many handrails are required on a stair 8m wide?

10. Barriers are governed by which compliance document?

11. What are two typical solutions for a slip resistant surface on an exterior timber ramp?

12. What would the pitch line be with for a common stair with a 190 tread, 280 rise and 25mm noser ?

100mm (child’s head).

Opening window is >1.0m form ground, children present.

Height, Barrier, restrictor

Private and service stairs.

Common stairs where children don’t frequent, only if an accessible stair is available.

310mm

Top and bottom of a stair, maximum vertical rise, arresting falling user

2

3 (5 best practice)

F4 Safety from falling

Polyurethane with grit, pvc mesh stapled to deck, profiled with test

36.5 deg

Lecture Content Review Quiz



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END

Stair Types – Decisions/Decisions Game

Stair Types:

Stairs Terminology

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