Target Fixings Limited

Dri Flex ties were developed as a result of the identified need to drill smaller holes in masonry to control the amount of spalling caused when drilling the near leaf. A large hole drilled through a brick using a SDS hammer drill can result in up to half of it spalling away. This material can cause bridging of the cavity and moisture transfer, and leaves a much reduced fixing thickness for the near leaf connection. Drilling for the Dri Flex tie requires hole sizes reduced to between 5mm and 7mm, which dramatically reduces the spalling of the brick. Dri Flex offers the advantage of a non-expanding mechanical fixing to both the far and near leaf. Pre-installation testing should be performed to the requirements of local standards and technical help and advice is available. Because the fixing method employed does not induce additional stress into the substrate, Dri Flex can be used in many and varied materials, from poured concrete columns to aircrete blocks, with satisfactory results. Edge spacings, so critical with any expansion-type fixing, are not a requirement with Dri Flex.

The design of Dri Flex remedial tie ensures that any potential for installer error can be minimised. The multiple drip design of each fin allows the Dri Flex to be installed at an angle of up to 25° towards the inner leaf without the possibility of any water transfer across the cavity. It is recommended that each Dri Flex is installed horizontally.

• One piece design - no moving parts to lose.
• Multiple drip points to deter water transfer.
• Flexible design allows natural building movement.
• Fixes through insulation material.
• Minimal disfiguration to structures.
• Strong yet flexible connection.
• Lightweight installation equipment.
• Corrosion-resistant materials.

Dri Flex ties are manufactured from Grade 304 austenitic stainless steel. The 8mm diameter Dri Flex has a tensile strength in excess of 10kN. The manufacturing process produces very hard fins that are able to cut a thread into the hardest concrete, but maintains a very soft and flexible core. Dri Flex ties may also be used where there is a need for a fire resistance in excess of 30 minutes.

In general terms the fixing densities for Dri Flex remedial wall ties would be the same as new build - 2.5 per m² or 450mm vertically and 900mm horizontally in a domino five pattern. This density would, however, be subject to on site testing to ensure that the required tensile loadings are being achieved. It should also be borne in mind that around all openings - doors and windows - ties should be installed at no more than 300mm vertical centres and no more than 225mm from the edge of the opening. BRE Digest 401 gives more information on the proof load test requirements.

If the masonry is so weak or friable that the required proof test load for standard density fixings cannot be achieved, it is quite acceptable to increase the density of Dri Flex ties to ensure that the overall loading per m² is achieved.

Lowering the installation density below the standard is not recommended.

Because Dri Flex ties cannot be randomly tested on site, it is necessary to perform comprehensive preinstallation tests.

There are several different methods of performing tests, but the most straightforward way is to drill into both leaves as described in the Installation Procedures section above. The near leaf hole may then be overdrilled to 12mm. The Dri Flex tie should then be installed into the far leaf and a test performed using the Target Load Test Unit. The fixing capability into the near leaf material may ascertained by drilling into the near leaf as in the Installation Procedures section above and inserting the tie to a maximum depth of 80mm and then test using a Target Load Test Unit. It is recommended that testing is performed in accordance with the requirements of BRE Digest 401. Only in exceptional circumstances does the proof test load requirement exceed 1kN.