3.1 Dimensional Tolerance
Panel Thickness 3/8” or 1/2” (10 or 13 mm).....................................................................................................±1/32” (± 0.8 mm)
Panel Thickness 3/4” to 1 5/8” (19 to 41 mm)....................................................................................................... ±1/8” (± 3 mm)
Panel Thickness Greater than 1 5/8” (41 mm).......................................................................................................±1/4” (± 6 mm)
Panel Face Dimension......................................................................................................................................... ±1/16” (± 1.5 mm)
Face Variation from Rectangular (Maximum out of Square) (Non-Cumulative)........................................ ±1/16” (± 1.5 mm)
Heads / Calibrated Edges................................................................................................................................... ±1/16” (± 1.5 mm)
Quirk Miters (Width of Nose) up to 1/4”................................................................................................................. -0, +25% of dim
Quirk Miters (Width of Nose) over 1/4”..................................................................................................... -0, +1/16”(–0, +1.5 mm)
Location of Back Anchors.......................................................................................................................................... ±1/8” (± 3 mm)
Depth of Back Anchors................................................................................................................................-0, +1/16” (-0, +1.5 mm)
Location of Holes for Precast Anchors......................................................................................................................±1/4” (±6 mm)
Hole Depth for Precast Anchors........................................................................................................................... ±1/16” (±1.5 mm)
Anchor Slots - From Face to Centerline of Slot.................................................................................................. ±1/16” (±1.5 mm)
Anchor Slots - Lateral Placement...............................................................................................................................±1/4” (±6 mm)
Anchor Slots - Width................................................................................................................................................ ±1/16” (±1.5 mm)
Anchor Slots - Depth at Maximum...............................................................................................................................±1/8” (±3 mm)
Anchor Holes - From Face to Centerline of Hole............................................................................................... ±1/16” (±1.5 mm)
Anchor Holes - Lateral Placement..............................................................................................................................±1/8” (±3 mm)
Anchor Holes - Diameter........................................................................................................................................ ±1/16” (±1.5 mm)
Anchor Holes - Depth.....................................................................................................................................................±1/8” (±3 mm)
Anchor Sinkages - Depth...................................................................................................................................-0, +1/8” (-0, +3 mm)
Continuous Kerfs - From Face to Centerline of Kerf......................................................................................... ±1/16” (±1.5 mm)
Continuous Kerfs - Maximum Bow in 4’-0” (1.2m)............................................................................................ ±1/16” (±1.5 mm)
Continuous Kerfs - Width....................................................................................................................................... ±1/16” (±1.5 mm)
Continuous Kerfs - Depth.............................................................................................................. -1/16”, +1/8” (-1.5 mm, +3 mm)
Rebated Kerf Elevation of Bearing Surface........................................................................................................ ±1/16” (±1.5 mm)
Bearing Checks – Elevation of Bearing Surface................................................................................................ ±1/16” (±1.5 mm)
Bearing / Clearance Checks – Lateral Location.....................................................................................................±1/2” (±13 mm)
Bearing / Clearance Checks – Setback from Face............................................................................................ ±1/16” (±1.5 mm)
Comment: TOLERANCES AND THICKNESSES: The suggested minimum nominal thickness for exterior veneer is as follows:
Bush hammered finish..................................................................................................4” (102 mm)
Pointed finish............................ ......................................................................................4” (102 mm)
For all other finishes a minimum nominal thickness of granite panel is to be determined pending analysis of the following criteria:
A. Piece Size
B. Face Finish
C. Anchoring Method & Location
D. Structural Design Load Requirements
Comment: It is more economical if the granite panel thickness coincides with one of the industry standard nominal thicknesses of 4” (102 mm), 3” (76 mm), 2” (51 mm), 1 5/8” (41 mm) or 1 1/4” (32 mm).
3.2 Flatness Tolerances
Variation from true plane, or flat surfaces, shall be determined by a 4’ dimension in any direction on the surface.
Such variations on polish, hone, and fine rubbed surfaces shall not exceed tolerances listed below or 1/3 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 1/2 of the specified joint width, whichever is greater.
Polished, honed or fine rubbed finishes.................................................................... 1/16” (1.5 mm)
Sawn, 4-cut, 6-cut, and 8-cut finishes............................................................................... 1/8” (3 mm)
Thermal and coarse stippled finishes............................................................................ 3/16” (5 mm)
Pointed or other rough cut finishes...................................................................................... 1” (25 mm)
3.3 Beds and Joints
Comment: BED AND JOINT WIDTH: The minimum recommended joint width is 3/8” for pieces with sawn beds and joints. Larger joint widths are required if pieces have split or otherwise rough cut beds and/or joints.
Pieces shall be bedded and jointed as shown on the approved shop drawings, and bed and joint surfaces shall be cut as follows:
1. Bed and joint surfaces shall be sawn through the full thickness of the granite piece. Bed and joint surfaces shall be within ±3° of 90° to the face of the piece unless otherwise specified.
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Comment: This specification is recommended for most applications where a 3/8” bed or joint width specification is used.
2. Beds and joints shall be sawn or cut full square 2” back from the face and from that point may fall under square not more than 1” in 12”. Both beds and joints shall be reasonably free of large depressions.
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Comment: This or similar specification is recommended for pieces 4” 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 rough sawn generally square with the face and may fall under square with the face not more than 2” in 12”.
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Comment: This or similar specification is recommended only for projects with bed and joint widths of 3/4” or more where a split face or other rough sawn appearance is specified.
3.4 Backs of Pieces
- Comment: SAWN BACKS: Because of physical characteristics, most granite cannot be split to a thickness less than one-third the lesser face dimension. Consequently sawn backs (the first specification) should be specified for most veneers, and are frequently specified also for thicker ashlar, because of design considerations.
A. Installer’s Option of one of the following:
1. Backs of all pieces shall be sawn to approximately true planes.
- Comment: Recommended for most building granite specifications.
2. Backs of all pieces may be either rough or natural quarry split to provide surfaces, which vary not more than 1” in 12” from true plane and not more than 2” from their specified thickness.
- Comment: Recommended for structural bridge piers, 4” or more split face pieces, or other installations of thicker pieces where a sawn back is not required.
B. Fabricate stone to maintain minimum clearance of 1” between backs of stone units and surfaces behind stone.
C . All tolerances listed assume panels 4” or less in thickness, not more than 5’ x 5’, and sawn on all six sides.
- Comment: For thicker pieces, very large pieces, or pieces with split, pointed or rough sawn faces, backs, beds or joints, tolerances generally must be increased. Consult with suppliers on tolerances for special pieces.
D. A minimum cavity void of approximately 1” (25 mm) shall be maintained behind ashlar or dimensional granite used as a veneer. This cavity should be adequately ventilated and wept to eliminate the accumulation of moisture behind the granite veneer.
- Comment: The NBGQA recommends a minimum factor of safety of 3.0 to 1 for granite panels and a minimum factor of safety of 4.0 to 1 for all anchorage assemblies.
3.5 Fabrication, General Requirements
A.Mouldings, washes and drips shall be constant in profile throughout their length, in strict conformity with details shown on approved shop drawings.
B. Dress joints straight and at 90 degree angle to face. Shape beds to fit supports.
C. Anchor Provision: Cut and drill sink provisions and holes in stone for anchors, fasteners, supports, and lifting devices as indicated or needed to set stone in place.
D. Allow room for expansion of the anchoring devices where necessary.
E. Where liners are required on the back of panels, secure by means of mechanical anchors. Comply with referenced standards.
F. Finish exposed faces and edges of stone, except sawed reveals, to comply with requirements indicated for finish and to match final samples
and mockups.
G. Joint Width: Cut stone to produce uniform joints 3/8” or as shown on Drawings.
H. Provide chases, reveals, reglets, openings, and similar features as required to accommodate adjacent work.
I. Grade and mark stone to achieve uniform appearance when installed. Inspect finished stone units at fabrication plant. Replace defective units.
3.6 Incidental Cutting and Drilling
Panels in excess of 100 pounds (45 kg) may include, at installer’s option, lifting clamp dimples, Lewis holes, or other provisions as required to acommodate the lifting device(s) utilized by the installing contractor. Lifting holes in the top beds of panels or other locations where moisture collection is likely to occur shall be filled with non-expanding grout or high-modulus elastomeric sealant after installation and final alignment.
