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For clarity, the following terms are defined in relation to wire barriers:
Openings in barriers (including decorative barriers) must be constructed so that any opening does not permit a 125mm diameter solid cone to pass through it. For stairs, the space is measured above the nosing line.
To comply with this requirement, spacing of support posts (post or rail spacing), wire tension, deflection and lay of wire (number of strands by the number of individual wires in each strand) are specified within the National Construction Code (NCC).
The installer needs to ensure that the required wire tension is achieved and maximum permissible deflections are not exceeded. The tension can be measured using a strain indicator, if available, or the deflection can be measured using a 2kg mass suspended at mid-span on the wire between support posts.
The tension and deflection measurements will depend on the type of wire used, support post or rail spacing, wire diameter and lay and wire spacing. Refer to the tables below from NCC Volume Two 2019.
It is important to read the notes to the tables as they provide additional information on their application to horizontal, vertical and near-vertical wire barriers.
In horizontal systems and non-continuous vertical wire barriers, the maximum spacing is 100mm and for continuous vertical wire systems 110mm.
Other provisions include:
Care and maintenance are necessary to ensure that the wire tension will be maintained during the life of the barrier. In some situations, it is necessary to install 'locking oft' devices to prevent loosening of wires.
NCC Volume Two Table 3.9.2.1 Wire barrier construction — Required tension for stainless steel horizontal wires
Clear distance between posts (mm) | |||||||||||
600 | 800 | 900 | 1000 | 1200 | 1500 | 1800 | 2000 | 2500 | |||
Wire dia. (mm) | Lay | Wire spacing (mm) | Minimum required tension in Newtons (N) | ||||||||
2.5 | 7x7 | 60 | 55 | 190 | 263 | 415 | 478 | 823 | 1080 | 1139 | X |
80 | 382 | 630 | 730 | 824 | 1025 | 1288 | X | X | X | ||
100 | 869 | 1218 | 1368 | X | X | X | X | X | X | ||
2.5 | 1x19 | 60 | 35 | 218 | 310 | 402 | 585 | 810 | 1125 | 1325 | X |
80 | 420 | 630 | 735 | 840 | 1050 | 1400 | 1750 | X | X | ||
100 | 1140 | 1565 | X | X | X | X | X | X | X | ||
3.0 | 7x7 | 60 | 15 | 178 | 270 | 314 | 506 | 660 | 965 | 1168 | 1491 |
80 | 250 | 413 | 500 | 741 | 818 | 1083 | 1370 | 1565 | X | ||
100 | 865 | 1278 | 1390 | 1639 | X | X | X | X | X | ||
4.0 | 7x7 | 60 | 5 | 73 | 97 | 122 | 235 | 440 | 664 | 813 | 1178 |
80 | 196 | 422 | 480 | 524 | 760 | 1100 | 1358 | 1530 | 2130 | ||
100 | 835 | 1182 | 1360 | 1528 | 1837 | 2381 | 2811 | 3098 | X | ||
4.0 | 1x19 | 60 | 5 | 5 | 10 | 15 | 20 | 147 | 593 | 890 | 1280 |
80 | 30 | 182 | 300 | 415 | 593 | 1105 | 1303 | 1435 | 1844 | ||
100 | 853 | 1308 | 1487 | 1610 | 2048 | 2608 | 3094 | 3418 | 3849 | ||
4.0 | 7x19 | 60 | 155 | 290 | 358 | 425 | 599 | 860 | 1080 | 1285 | 1540 |
80 | 394 | 654 | 785 | 915 | 1143 | 1485 | 1860 | 2105 | 2615 | ||
100 | 1038 | 1412 | 1598 | 1785 | 2165 | 2735 | X | X | X |
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Notes to Table 3.9.2.1
Table 3.9.2.2 Continuous wire barrier construction — Required tension for vertical or near vertical stainless steel wires
Wire dia. (mm) | Lay | Widest spacing between wires (mm) | Maximum clear spacing between rails (mm) |
900 | |||
Required tension in Newtons (N) | |||
2.5 | 7x19 | 80 | 145 |
100 | 310 | ||
110 | 610 | ||
2.5 | 7x7 | 80 | 130 |
100 | 280 | ||
10 | 500 |
Notes to Table 3.9.2.2
Table 3.9.2.3 Continuous wire barrier construction — Maximum permissible deflection for stainless steel wires
Clear distance between posts (mm) | |||||||
600 | 900 | 1200 | 1500 | 1800 | 2000 | ||
Wire dia. (mm) | Wire spacing (mm) | Maximum | |||||
2.5 |
60 | 17 | 11 | 9 | 8 | 8 | 8 |
80 | 7 | 5 | 5 | 5 | X | X | |
3.0 | 60 | 19 | 13 | 8 | 7 | 7 | 7 |
80 | 8 | 6 | 6 | 5 | 5 | 5 | |
4.0 | 60 | 18 | 12 | 8 | 8 | 7 | 7 |
80 | 8 | 6 | 4 | 4 | 4 | 4 |
Notes to Table 3.9.2.3
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