Tooling Mortar Joints

As the mortar between laid bricks begins to cure, the surfaces of the horizontal (bed) and vertical (head) joints will need to be tooled or troweled. Tooling will compress the mortar and decrease moisture absorption at the surface. Tooled joints provide the greatest barrier against infiltration of water, whether from wind-driven rain, ice or snow. Troweling consists of cutting or striking off a joint using a trowel. This type of joint is generally less effective at shedding water. It is important to tool or trowel joints at a consistent moisture content so that they do not appear light in some areas and dark in others. You'll know that joints are ready for tooling or troweling when the mortar is "thumbprint" hard — meaning you can press your thumb against the mortar and leave a print impression without any mortar sticking to your thumb.

Types of tooled and troweled joints
Of the tooled joints, the concave joint is the most common. It gives a wall a fairly uniform appearance. V-joints, on the other hand, emphasize shadows. Among troweled joints, the raked joint — which leaves the mortar perpendicular and recessed almost 1/2 inch, thus creating dark shadows — has the least weatherability and should be used only on interior walls. Beaded joints have a formal appearance and create strong shadow lines, as do both struck and weathered joints. Of the troweled joints, the weathered joint is the only one effective at shedding water. Flush joints are only acceptable in areas not subjected to heavy rain and snow. The struck and weathered joints are good for creating strong shadow lines on a wall. The concave and V-joints are the most weather-resistant because they compact the surface of the mortar as it is tooled. (Fig. 1)

Joint types can be mixed in any one project. For example, you can combine flush vertical joints with beaded horizontal joints to produce long horizontal shadows. However, mixing joint styles in a pleasing manner is difficult to do, even for a professional.