A. W. HENDRY University of Edinburgh

The paper discusses, on the basis of experimental results, the various workmanship factors which influence the strength of masonry. Most of the quantitative information relates to the compressive strength of brickwork. The relative importance of the various defects has been assessed and the factors most likely to result in loss of strength include: incorrect proportioning and mixing of mortar; incorrect adjustment of the suction rale of masonry units; incorrect jointing procedures; disturbance of units after laying; failure to build walls “plumb and true to line and level”; failure to protect new work from the weather. Incompletely filled or over thick bed joints may reduce the strength of brickwork by 25%. A combination of defects could halve the strength of the wall but they would be so obvious as to fail the most rudimentary inspection. The implications are discussed in terms of safety factors and it is concluded that these will result in about the same level of safety over the range of manufacturing and site control envisaged as acceptable in BS5628.