wash, nor will paint cover them. Allow droppings to dry and harden. You can then chip off most of the mortar with a small piece of broken concrete block (figure 8-29, view 1) or with a trowel (view 2). A final brushing of the spot removes practically all the mortar (view 3).

RETAINING WALLS

The purpose of a retaining wall is to hold back a mass of soil or other material. As a result, concrete masonry retaining walls must have the structural strength to resist imposed vertical and lateral loads. The footing of a retaining wall should be large enough to support the wall and the load of the material that the wall is to retain. The reinforcing must be properly located as specified in the plans. Provisions to prevent the accumulation of water behind retaining walls should be made. This includes the installation of drain tiles or weep holes, or both.

PAINTING CONCRETE MASONRY

Several finishes are possible with concrete masonry construction. The finish to use in any specific situation should be governed by the type of structure in which the walls will be used and the climatic conditions to which they will be exposed.

Paints now commonly used on concrete masonry walls include portland cement paint, latex paint, oil-based paint, and rubber-based paint. For proper application and preparation of the different types of paint, refer to the plans, specifications, or manu- facturer's instructions.

Figure 8-29.-Cleaning mortar droppings from a concrete block wall.