Report R 117 Replacement ties in cavity walls: a guide to tie spacing and selection

Publication Year

1988

Document Status

Current

Abstract

Replacement ties are needed between the leaves of masonry cavity walls in cases where the original ties have corroded, are inadequately fixed, or are insufficient in number, such that the wall is unable to resist lateral load adequately without remedial work. The range of replacement ties which are currently marketed are described by reference to their generic features. The two common types are the chemical (resin) anchor and the expansion fixing. A series of 130 small-scale tests was carried out for typical replacement ties in different masonry materials, in order to determine their characteristic strength in tension and compression. In the tests, most forms of replacement tie fixed into masonry were found to be stronger than traditional butterfly ties. Seven large-scale tests were carried out on walls under lateral load, with replacement ties spaced much more widely than is currently required. On the basis of these tests a relaxation in tie distribution is proposed for certain cases. Two methods are given for assessing the optimum spacing of replacement ties: a calculation method, and a simple points system to determine the relative importance of the various parameters describing the wall, the location of the wall and the type of replacement tie used. When applying the guidance given, it is important to inspect adequately the particular walls in question and to ensure quality control of replacement tie installation and testing procedure.

ISBN

9780860172987

Publisher Information