5. Be sure the joints are damp, and then apply the mortar by placing it tightly into the joints in thin layers.
6. Tool the joints to smooth, compact, concave surfaces.
Another problem area easily detected during a routine inspection is efflorescence. Efflorescence usually appears as a light powder or crystallization caused by water-soluble salts, deposited as water evaporates within the mortar or the masonry unit. Aside from detracting from the appearance of a wall, efflorescence may indicate the penetration of moisture into the wall to an extent that could cause deterioration of interior wall coverings and finishes. Efflorescence may be removed by vigorous and repeated scrubbing with a stiff fiber or wire brush and clean water. An inspection should be made, however, to determine the source of the stain. If efflorescence appears at the edges and not near the center of the masonry unit, the mortar is probably at fault; if it appears near the center of the unit only, the masonry unit is at fault. The most immediate remedy to prevent recurrence of efflorescence is to check causes of excessive moisture that contacts the wall, such as defective flashings, gutters, downspouts, copings, and mortar joints.
Leakage through concrete walls is caused by cracks in the concrete and, in rare cases, porosity of the concrete. As with brick walls, the cracks may be caused by foundation settlement, excessive floor loadings, temperature settlement, contraction in structural members, or poor materials and poor workmanship in the original construction. The types of cracks encountered include horizontal movement cracks, vertical and diagonal movement cracks, and shrinkage cracks. An engineering investigation of the causes of structural defects should govern the nature and extent of major repairs.
HORIZONTAL MOVEMENT CRACKS are usually long, wide cracks in the mortar joints that occur along the line of the floor or roof slab or along the line of lintels over the window. Where these cracks turn the corner of a building, they frequently rack down, as discussed later. Figure 7-3 shows a typical horizontal movement crack and racked-down corner.
VERTICAL AND DIAGONAL MOVEMENT CRACKS generally occur near the ends or offsets of buildings. They may also be found extending from a windowsill to the lintel or a door or window on a lower floor. They vary from one eighth to three eighths of an inch in width and follow the mortar joints, but in some instances, they may break through the bricks or other 7-10 masonry. A diagonal movement crack is shown in figure 7-4.
SHRINKAGE CRACKS are the fine hairline cracks that are found in mortar as well as in concrete walls. The most noticeable ones are those running vertically, but a close examination of a section of a wall that leaks may also show them in the horizontal or bed joints of brick or block walls.
RACKED-DOWN CORNERS occur where the horizontal movement cracks along the side and end of a building meet. Frequently, the horizontal crack not only continues around the corner but forms part of a diagonal crack that takes a downward direction and meets a similar crack from the other side, forming a "V". The bricks inside this "V" are loosened and must be reset.
Figure 7-3. - Typical horizontal movement and racked-down corner cracks.
Figure 7-4. - Diagonal movement crack.Continue Reading