Discussion on session 3

MR HOLLAND (introducing Paper 12)

Durable masonry requires materials that are appropriate to the environment coupled with good detailing. Sometimes the environment changes as, for example, where de-icing salts come into contact with a structure. Sometimes the detailing demands a more durable material as is the case when raked joints in brickwork are used. Many bricks have a hard outer skin which can be damaged by over-enthusiastic cleaning such as sand-blasting. Other bricks, such as London Stocks, are more forgiving probably because their coarse non- interconnected pores are rarely filled.

Since my paper was written a most interesting publication of the Swedish Council for Building Research 'Salt disintegration1 by Joseph Ptihringer has been produced which describes the recent decay of masonry of considerable age and throws new light onto the movement of salts in masonry.