Metropolitan University of Leeds and J J. BROOKS University of Leeds

Previous investigators have shown that for certain types of clay brick, the horizontal irreversible moisture expansion of the clay brick masonry can be related to the unrestrained moisture expansion of the corresponding unbonded brick in the form of a ratio, which in the UK is usually taken to be 0.6. However, the brickwork/brick expansion ratio has been shown to depend on the type of brick used. For movements in the vertical direction, no equivalent ratio exists due to the lack of experimental data, although recent research suggests that the vertical expansion ratio is greater than in the horizontal direction. Test data are reported for 160d vertical moisture movement strain of 2-brick widex 13-course high single-leaf clay masonry walls constructed from seven types of unit with a 1: 1.5: 4.5 ordinary Portland cement:lime:sand mortar. When these are compared with the corresponding moisture expansion of the seven types of unbonded unit, it can be seen that the expansive behaviour of the unbonded unit does not always represent that of the corresponding masonry. In some cases the bonded unit appears to exhibit an expansion far in excess of that measured in the unbonded unit, that is, there appears to be an enlarged moisture expansion.