Technical Data

GRK Fasteners utilizes strict quality control procedures. Every batch of screws produced is independently random sampled and quality controlled to the highest standards.

Accreditations for independent test laboratories include:
ICC, CNLA, TÜV, Ü, ISO, DAR.

Tests conducted in Douglas Fir specific gravity 0.5.

Pull Out Test Results for RSS™ Structural Screws    
Size Sidegrain: Endgrain:
5/16 x 2"1/2 1740 lbs 1223 lbs
5/16 x 3"1/8 2054 lbs 2321 lbs
5/16 x 4" 2644 lbs 2565 lbs
5/16 x 5"1/8 2745 lbs 2829 lbs
5/16 x 6" 3619 lbs 3522 lbs
3/8  x 7"1/4 3962 lbs 3920 lbs
3/8  x 8" 4364 lbs 4661 lbs
3/8  x 10" 4840 lbs 5104 lbs
3/8  x 12" 5258 lbs 5044 lbs
3/8  x 14"1/8 5306 lbs 5172 lbs
3/8  x 16" 5990 lbs 5753 lbs
Shear Strength Test Results for RSS™ Structural Screws
Size Shear Values
5/16 x 2"1/2 829 lbs
5/16 x 3"1/8 847 lbs
5/16 x 4" 1328 lbs
5/16 x 5"1/8 1331 lbs
5/16 x 6" 1335 lbs
3/8  x 7"1/4 1282 lbs
3/8  x 8" 1386 lbs
3/8  x 10" 1504 lbs
3/8  x 12" 1900 lbs
3/8  x 14"1/8 1958 lbs
3/8  x 16" 2065 lbs
Head Pull Through Test Results for RSS™ Structural Screws. 
5/16" screws avg. 825 lbs
Shaft Diameter 0.198"
Head Diameter 0.616"
3/8" screws avg. 889 lbs
Shaft Diameter 0.220"
Head Diameter 0.711"
Shear Test Result for R4™ Multipurpose Screws
Diameter Avg. Ultimate Load (lbs) Wood Failure Rate
#4 139 50%
#6 301 70%
#8 361 30%
#9 452 65%
#10 687 75%
#12 720 75%
Minimum Tensile Strength
GRK Spec: 139,000 PSI
Code Spec: 45,000 PSI
Minimum Bending Angle
GRK Spec: 35°
Code Spec: 15°
Bending Yield Moment Test for RSS™ Structural Screws
5/16": 159,073 PSI
3/8": 177,241 PSI
GRK Certifications include:
ISO 9001
ICC
Ü – German Institute for Building Technology

Test stopped after wood failure or 1/8" screw displacement.

All tests were conducted at independent laboratories in the United States, Germany and Taiwan. Tests were conducted in accordance with ASTM and/or DIN norms.
Testing is ongoing and is conducted on every production series. All posted results are Average Ultimate Load Values.
For construction design purposes an applicable safety margin should be applied. An architect or engineer should be consulted for this.