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This page shows two diagrams which illustrate how the Gripple Tie-down system works. As was described in the article "Ode to a Gripple", gripples are part of the fence-straining family and are applied here in a similar fashion. The tensioning system is cheaper in cost and easier to apply than the all-thread method. It can even be applied in a diagonal fashion to aid bracing and rigidity. The 2.5mm high tensile wire cable can be slipped through tunnels of poly-pipe laid in the concrete at the time of pouring, or can pass through stout, galvanised eyebolts set either side of the top of the stem wall so that the wire passes under the bales. It is preferable to have the wire as two half loops, rather than cut and tied at the base. This means less bits of wire to cut, and a saving of time when it comes to tying off all those ends. Where the wire goes over the top-plate, it is debatable as to whether any wedges or shielding for the top edge of the top bale is required. In our experience we have found that with a wide top-plate the wire will cut into the top bale and find its own position. It does prove to be quite a pain trying to locate a shield either side, and in the end it was decided that the wedges and/or shielding were an unnecessary complication. The wire triangulates to its own line of least resistance, and maximum strength is assured. The picture to the left shows a section view of a wall. The wire attachment points would not actually be as far apart at the base as shown. That was a bit of artistic license to make the wires visible! The picture below is a perspective of a wall from slightly above showing the top-plate details, tie-down system and footing detail. |
