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Cladding (vertical)
The following are NOT intended as specific recommendations for any particular project. It is simply to be used as a general reference or guide to the specification process. It is the responsibility of the architect to specify the exact fixing requirements of a project based on its individual merits, and the property values of the stone selected.
The façade of a building is it's outer skin consisting of a combination of cladding and supports attached to the main structural frame. Modern dimension stone processing methods, in conjunction with modern construction materials and practices, have enabled stone cladding to be produced at a price and quality that make it a very attractive proposition for commercial projects. The cost and handling difficulties associated with solid stone walls are no longer a consideration as thin stone panels, (generally ranging from 20mm to 30mm thick - depending on specific application, location, and stone properties), can be safely band cost effectively secured to façade of any construction providing an attractive and durable finish to any project.
The most common form of fixing cladding to a structure, is to have the panels tied back to the building structure using angles or brackets. The brackets are fitted to the stone panels through a number of means all involving either cutting or drilling fixing slots in specified locations as shown on the shop drawings. These fixings in turn can be attached either too reinforced concrete walls, concrete bricks and blocks, or fastened directly to a steel frame
Cladding Installation
Before installation of any stone cladding to either the interior or the exterior of a project a number of design considerations must be taken into account.
The physical properties/characteristics of the stone, as provided by the supplier
Design loads and safety factors for the cladding
Expected wind loads on the exterior building - calculated from AS1170.2, or for small structures, calculated from AS1288 Appendix D.
Possible dimensional changes to the building due to wind-load sway, thermal expansion/contraction, seismic movement, creep and shrinkage.
Height above the ground at which the panel is to be affixed.
Consideration of the above factors will assist in determining the size and thickness of the cladding panels, and the type of fixing/anchoring system to be employed.
Panel Dimensions
The selection of an appropriate panel size and thickness (as mentioned above) is dependent on a number of critical factors that must be considered prior to final specification. It should also be kept in mind that there are restrictions to panel sizes based on limitations of processing equipment size of quarried material and the type and size of fixing and anchoring system employed.
As a general rule however "continuously supported hard stone panels (granite, marble, travertine?) below 3.7m above ground level should be at ,east 20mm thick, and soft stones (limestone, sandstone) 50mm thick. When more than 3.7m above ground level hard stone should be at least 40mm thick and soft stones 75mm thick."
NATSPEC Pg2.45 "Panel Dimensions"
It should be noted, that over specification of a panels thickness will incur additional material cost, where a thinner material may satisfy requirements equally as well.
Dimensional Tolerances
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Panel Thickness 10 or 13mm ± 0.8mm
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Anchor Holes - Lateral Placement: ± 3mm
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Panel Thickness 20 to 41mm ± 3mm
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Anchor Holes - Diameter: ± 1.5mm
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Panel Thickness Greater than 41mm ± 6mm
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Anchor Holes - Depth ± 3mm
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Panel Face Dimension ± 1.5mm
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Anchor Sinkages Depth @ Maximum -0 ± 3mm
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Face variation from rectangular ± 1.5mm
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Continuous Kerfs - from face to
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Maximum out of Square) (non-Cumulative)
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C/L of Kerf: ± 1.5mm
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Heads/Calibrated Edges ± 1.5mm
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Continuous Kerfs
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Quirk Mitres (width of Nose)
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Maximum Bow 1.2m ± 1.5mm
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Up to 6m 0 + 25% of dim
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Continuous Kerfs - Width ± 1.5mm
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Location of Back Anchors ± 3mm
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Continuous Kerfs - Depth -1.5mm, +3mm
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Depth of Back Anchors -0 + 1.5mm
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Rebated Kerf
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Location of Holes for Precast Anchors ± 6mm
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Elevation of Bearing Surface ± 1.5mm
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Hole /Depth for Precast Anchors ± 1.5mm
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Bearing Checks -
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Anchor Slots - from face to C/L of Hole: ± 1.5mm
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Elevation of Bearing Surface ± 1.5mm
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Anchor Slots - Lateral Placement: ± 6mm
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Bearing /Clearance Checks -
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Anchor Slots -Width: ± 1.5mm
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Lateral Location: ± 13mm
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Anchor Slots Depth @ Maximum ± 3 mm
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Bearing Clearance Checks -
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Anchor Holes - from face to C/L of Slot: ± 1.5mm
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Setback from Face ± 1.5mm
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Anchor Types
An anchor is a metal shape inserted into a slot or hole in the stone that provides for a transfer of load from the stone to the building structure, In almost 100% of cases anchors should be produced from "Series 300"stainless steel . See AS 2975. Although other material types can be used for anchors, they are more liable to stain the stone.
Anchors must support the weight of the stone simultaneously experiencing wind pressure and suction loads on the panel/.
Diagrams and descriptions |
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The following general rules should be observed when considering fixing selection.
Connections should be simple, using the fewest possible components, and the fewest type of connection type within any project.
During the design process distribute the weight of each panel over no more than two anchors to simplify calculations.
Make sure connections are adjustable to accommodate tolerances in material and construction.
Flatness Tolerances
Variation from true plane, or flat surfaces, shall be determined by a 1200mm straight edge placed direction on the surface.
Such variations on polish, hone, and fine rubbed surfaces shall not exceed tolerances listed below or of the specified joint width, whichever is greater. On surfaces having other finishes, the maximum variation from true plane shall not exceed the tolerance listed below or half of the specified joint width, whichever is greater.
Polished, honed or fine rubbed finishes
- 1.5mm
Sawn, 4-cut, 6 -cut and 8-cut finishes
- 3 mm
Thermal and coarse stippled finishes
- 5mm
Split face, pointed or other rough cut finishes
- 25mm
-Connection locations must be accessible to installers during construction.
-Connection components should be designed to avoid trapping moisture.
Beds and Joints
Panels shall be bedded and jointed as shown on the approved shop drawings, and bed and joint surfaces shall be cut as follows:
(Three optional specifications: choose one or more depending on design criteria and types of panels utilised).
1. Bed and joint surfaces shall be sawn through the full thickness of the granite panel. Bed and joint surfaces shall be within ± 3% or 90º to the face of the panel unless otherwise specified.
(This specification is recommended for most applications where a 19mm bed or joint width specification is used).
2 - Beds and joints shall be sawn or cut full square 50mm back from the face and from that point may fall under square not more than 25mm in 300mm. Both beds and joints shall be reasonably free of large depressions.
(This or similar specification is recommended for panels 100mm or more in thickness when cost savings may be achieved by eliminating the above full sawn specification).
3 - Beds and joints shall be split or roughly cut generally square with the face and may fall under square with the face not more than 50mm in 300mm.
(This or similar specification is recommended only for projects with bed and joint widths of 20mm or more where a split face or other rough cut appearance is specified).
Butt joints should be avoided as any movement within the structure will be transferred directly to the panels, and damaged as a result. In addition butt joints do not provide an allowance for the cutting tolerances of the panels.
Book Matching
Book Matching the veining on adjacent panels is matched end-to-end, and side-to-side, to give the impression of one large "seam-less" panel. In order to produce this effect each corresponding panel must be cut from the exact same relative position in the slab as the previous panel.
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Bookmatch Cladding, Foyer, Rialto Tower, Melbourne
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