Suction into the walls, if the masonry units are absorbent and they have not been dampened.Evaporation, if the wall is not protected from sun and wind.These cracks normally occur when a plaster mix with high cement content is used or the plaster is allowed to dry too quickly.Ĭauses of excessive early moisture loss are: Map cracking is similar to crazing except that it is usually deeper (sometimes going through the plaster) and the hexagons of the pattern may measure up to 200 mm across. If necessary, glass fibre tissue can be applied during the painting operation. Crazing often occurs within a few hours of the plaster being applied to the wall and cracks may hardly be visible until dust or moisture makes them noticeable.Ĭraze cracks are of little importance, do not open and close with time, and can be covered using reasonable quality paint.
They are usually the result of over towelling a rich mix (one with high cement content) or using sand containing an excessive amount of dust (more than 15% by mass passing a 0,075 mm sieve). Craze cracks are usually very fine and shallow and do not extend through the whole depth of the plaster. The causes and repair methods for each are discussed below.Ĭrazing is a network of fine cracks, usually in a hexagonal pattern, which measures between 5 and 75 mm across each hexagon. Defects most frequently noticed in plaster fall into one of the following categories:
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