Helix Spiro Remedial Wall Ties

Replacement Wall Tie System

TYPICAL APPLICATIONS

Replacement of corroded or inadequate cavity wall ties in existing buildings.
Cavity ties far brick or block overcladding of existing buildings.

WALL TIE FAILURE

The Problem

The increasing incidence of wall-tie failure due to corrosion is now causing very serious concerns in many parts of the United Kingdom. The problem has arisen because the zinc coating applied to the mild steel ties used extensively to link cavity wall constructions was insufficient to prevent corrosion. Up to 1981, when the British Standard was amended to specify thicker coatings of zinc, the anticipated life of galvanised ties was only 15-20 years. It is now estimated by the year 2000, the ties used in 7 million buildings will have exceeded their minimum life expectancy.

Identification

Early identification of wall-tie failure is crucial before any serious structural damage occurs. Where conventional ties have corroded within the outer leaf of the wall . Characterstic cracking is evident as a regular pattern in the horizontal mortar joints. Carrying the ties, usually every 6th course. The position of the ties can be located by metal detector. Visual inspection by the removal of bricks or by the use of an endoscope can quickly confirm tie failure. Where corrosion has not occurred in the outer leaf, the first indication of wall-tie failure could be the collapse of all or part of the wall.

The Solution

Spiro-Remedial Ties provide an inexpensive and permanent solution to wall-tie failure. They offer the following advantages.

Austenitic stainless steel - as recommended by BRE Digest No.329
Unobtrusive - only requires a 10mm diameter drilled hole.
Can be fixed through either masonry units or mortar joints.
Installation using polyester or epoxy resin Spiro Remedial Ties to be fixed into a wide range of masonry and Concrete materials.
Continuous drip allows ties to he fixed horizontally - simplifies installation.

Specification

Spiro-Remedial Ties are manufactured from austenitic stainless steel Type 304 to BS1449. For particularly corrosive and aggressive conditions Type 316 stainless steel is available on special order.

Spiro-Remedial Ties are made from 2mm x7.5mm Spiro. The appropriate Spiro-Remedial Tie for a particular cavity width and situation should be specified. Contact us for details.

Installation

Using a 10mm masonry drill bit, horizontally drill through the brickwork of the outer leaf and into the inner leaf to give a measured hole depth of 70mm. Simple markers may be attached to the drill bit to establish cavity width (which coulld vary within the same wall) and the depth of hole in the inner leaf.
Remove all dust from the holes in both leaves using an airline or extended bottle brush and water.
Using an extension nozzle to reach the depth limit of the hole in the inner leaf; inject a suitable polyester or epoxy resin to fill the hole. The Ramset Chemset Injection System produced by Ramset Fasteners Ltd. is parcularly recommended for fixing Spiro-Remedial Ties.
Insert the Spiro-Remedial Tie into position.
Inject resin into the outer ieaf hole to bond the tie.
Point and make good with colour-matched mortar.

Notes

Before under-taking replacement of failed cavity wall-ties, it is essential to establish that the walls are otherwise sound, and that any damage arising from the corrosion of the ties has not seriously affected the structural integrity of the masonry.
It is recommended as good practice that the remains of all failed ties are completely removed from both outer and inner leaves.
A comprehensive range of specialist equipment is readily available to simplify the replacement of failed cavity ties. The range includes metal detectors to accurately. locate the position of existing ties, endoscopes for cavity inspection, and devices for in-situ sample tension testing of the replace— rent resin-fixed ties. .

STRUCTURAL PERFORMANCE

For details of structural performance contact us.