Closed mono-stringer
M1
design elements
Closed mono-stringer
design Almost a decade ago, Arden streamlined the domestic mono-stringer design for broad application in the Australian market, and with good reason this staircase format has become an industry standard. The MS1 evolves this basic structural technique to create a fully fledged commercial design. The intent of the MS1 is to create a proportionally significant and deceptively simple interior sculpture. Attention is drawn to the contrast in the snaking zigzag of warm polish timber and the linear sweep of the structural steel member, thus emphasising a simultaneous contrast in line and material. By default, the MS1 incorporates a thick monolithic hardwood tread and riser assembly so that no edge trim is required, and avoiding any possible distraction from the clean geometric lines of the staircase. The mono-stringer’s position underneath and away from the edges of the treads makes it retreat from view, and allows the impression of the staircase to be dominated by the zigzag tread and riser assembly when viewed from a forward position.
M1
Leveraging the strength of structural steel, the central beams of the mono-stringer can span large open spaces without support. Due to its visual simplicity, it can sit equally well in a modern office or public building; either alone, or surrounded by other structures. On exceptionally long spans a central column is applied to add the necessary support, while maintaining a slim metal stringer line.
Figure 1. Isometric overview of the MS1 showing a straight flight with landing. A variety of balustrade styles can be applied to the MS1, so a handrail is presented here only for visual reference. Figure 2. Plan and elevations of a sample MS1 design is indicative of a partial balustrade only.
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1
P2P
865 min,1000 max 865 min,1000 max 920 recomended 920 recomended
Upper floor Upper floor Flight Flight two two Riser Boards Riser Boards
1000
AS1428.1 AS1428.1 1 Going 1 Going + 300mm + 300mm
Rise Going
Treads Treads Tread support plates Tread support plates
Flight Flight One One Going
1000
Indicates line of handrail Indicates line of handrail
Stringer Stringer
Rise
Landing Landing Support Support pillar pillar
Plinth
Plinth
Closed mono-stringer
Clear Clear space space between between handrails handrails
Floor cover Floor cover
2
M1 design elements
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Solid wood treads and risers
Slip resistant safety strip also conceals screw heads.
Screws secure tread to riser
Going
32-42
32-42
While most mono-stringers only need two support points per flight, it must be kept in mind that the structure must provide strong rotational, as well as lateral and vertical support. Support bindings are usually in the form of a steel mounting plate with at least 4 points for bolts or other attachments. In some cases, the stringer can be welded directly to steel support beams in the existing structure. Two alternative tread designs are shown. The first shows a solid timber tread. If larger treads are required, solid wood of the required profile may be difficult to source. In this case, an alternative composite tread is applied, comprising a a veneer of dress timber over a structural ply or MDF core. Other designs and materials are possible: refer to Arden technical data sheet ‘A.3 Treads’ for details.
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Two piece welded orthagonal support plates for high load bearing staircases.
Vertical plate straddles SHS
SHS forms main span of mono-stringer
3
Solid wood treads and risers Screws secure tread to plate
Screws secure tread to riser
M1
There are also two alternative tread support plate designs. Light duty stairs may use the folded tread plate design. Where high design loads or a wide flight is specified, a heavier gauge steel tread plate is called for. This would make a folded design impractical, and we would therefore recommend the use of the two piece orthogonal welded design.
Go
in g
Figure 3. Solid timber tread. Figure 4. Isometric view of solid wood tread supported by welded tread plate and brace. Figure 5. Elevation with break out section of composite tread supported by folded tread plate.
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Screws secure tread to plate
Rise
The core member of the MS1 is constructed from SHS or RHS mild steel sections of a size suitable for the required loads and spans. These sections are mitred and welded at the angle points into a continuous solid member. Support plates for the treads and landings are welded to the core. Mounting plates are also usually welded where required at this stage.
Rise
Closed mono-stringer
technical
Two piece welded orthagonal support plates for high load bearing staircases. Vertical plate straddles SHS 4
SHS forms main span of mono-stringer
Closed mono-stringer
Screws secure tread to plate Composite tread and riser manufactured from MDF core with dress wood veneer Slip resistant safety strip
Folded tread plate Tread thickness as req'd
Plate straddles SHS for greater rigidity
5
SHS forms main span of mono-stringer
M1 design elements
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Composite tread and riser manufactured from MDF core with dress wood veneer
Folded steel tread plate
Slip resistant safety strip
6
M1 6
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Screws secure tread to plate
Plate straddles SHS for greater rigidity
J
Applied nosing/edge trim to conceal end grain.
Figure 7. Floor fixing to concrete on non-shrink grout.
D
Closed mono-stringer
Figure 6. Isometric view of composite tread supported by folded tread plate.
Closed mono-stringer
Optional plinth to conceal base and guard low overhead areas
Mild steel base plate
Non-shrink grout
7
M16 bolts chemically bonded to concrete floor.
M1 design elements
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Closed mono-stringer
Figure 8. Void edge mounting with visual connection detail. Figure 9. Void edge mounting with non-visual connection detail.
Edge nosing
Figure 10. Non-visual floor fixing method.
Chemical anchors for concrete floors Plaster board Visual connection detail
J
8
Upper floor cover
Top tread flush with upper floor coverings Riser board
D
Upper floor concrete slab
Concealed connection detail
Tread support plate
M1 Chemical anchors for concrete floors Plaster board SHS main span
Suspended ceiling 9
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Concrete recessed to conceal connection
35.8째
M12 chemical anchors 10mm (typical) base connection plate
200
55
Closed mono-stringer
Floor coverings
10
M1 design elements
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Closed mono-stringer
7
Figure 11. Non-visual wall fixing method. Figure 12. Typical stringer to stringer connection detail
Concrete recessed and plastered over to conceal connection 200 SHS of stringer
M12 chemical anchors 10mm (typical) connection plate welded to end of SHS
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Under landing section of upper flight stringer
Dome nuts secure lower stringer to threaded rods welded to upper stringer Raked section of lower flight stringer
J
Bracket to support landing
12
J
M1 10
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10mm end plate welded to lower stringer
Intellectual property is copyright Š Archstairs Pty Ltd unless otherwise agreed in writing. All rights to the document are retained. Any use of the document by clients or third parties, unless specifically authorised by Archstairs Pty Ltd, are at their own risk and the user releases and indemnifies Archstairs Pty Ltd from and against all loss or damage arising from such use.
Closed mono-stringer
About this document
compliance Arden is a BSA licensed contractor for carpentry, joinery, glass, glazing and aluminium as well as structural metal fabrication and erection. Arden supplies a Form 16 (Licensed Contractor) on all projects. In design and construct contracts, a Form 15 (Design Engineer) certification is supplied upon request. For products and services incorporating the M1 system, this table shows compliance with relevant codes and standards.
Key full compliance with the code can comply not applicable to this element
Code
Title
BCA
The Building Code of Australia
Applicability
AS NZS 1170.1-2002
Structural Design Actions – Permanent, imposed and other actions
AS 1288-2006
Glass in Buildings. Selection and installation.
AS NZS 1554.1-2004
Structural steel welding - Welding of steel structures
AS 1554.6-1994
Welding stainless steels for structural purposes
AS NZS 4586-2004
Slip resistance classification of new pedestrian surface materials
AS 1428.1-2009
Design for access and mobility
AS 1657-1992
Fixed platforms, walkways, stairways & ladders. Design, construction and installation
M1
design note For all commercial applications, it is important that sufficient space for the stairwell cavity be allowed to satisfy Australian Standards and BCA requirements. The footprint is primarily driven by the floor to floor rise, as well as the staircase configuration chosen. However, stringer and balustrade style design may increase the amount of space required. Allowing too small a cavity can restrict the design options of the staircase. Also, points at where the staircase interacts with other structures are best addressed early in the design cycle. Consultation with Arden early on will help ensure that these design issues can be addressed in a cost-effective manner.
design elements
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