When there is a brick building in the subject, you are faced with a choice of two options: ignore the bricks and just paint the whole house with a brick color, or paint each brick individually. What you choose depends on various factors: Is the house far away or close by? Do the bricks contribute to the painting or is it just a messy confusion? Is there strong perspective on the brick building? There are many different factors that can guide the choice. Sometimes you should paint everything with the same color and sometimes it is actually better to paint all the bricks.
If you decide to paint bricks, you need to draw them first. It is very important, if you paint freehand you will not be able to keep even lines. If the house is to be credible, it is important that the bricks lie in fine lines that follow the perspective. I usually draw lines for the rows and then vertical lines for each stone. You have to think about how the bricks are laid, which bond patterns are used. Then I paint the bricks almost to the line, thus creating a space between each brick and the mortar.
I usually use a smaller brush to paint bricks, but one of my students coined the word brick brush to refer to a flat synthetic brush the right size for a brick. With such it is easy to paint bricks quickly and efficiently, I myself like the less regular ones that are painted with a regular brush but a “brick brush” is an effective tool.
Also think about making the stones slightly different in color, they might be the same on the house you are painting, but it will be a bit boring in a painting. Before they are dry, you can also place a dab of a contrasting color in some of the stones to suggest unevenness.
Once all the bricks are painted, let them dry and then you should paint the mortar between the bricks. A light gray color is used for this. It is very important that you do not just leave the spaces white. Before the mortar has dried, you can put a few splashes of darker color here and there.
The last thing to do to get believable bricks is to paint a very thin shadow under some of the bricks, it doesn’t have to be on all of them. The side of each stone should also have a small shadow, on the left side if the light is coming from the right or vice versa if the light is coming from the other direction.
Some examples of bricks in watercolor paintings