Science Puzzle
Why Are Bricks Laid in an Overlapping Pattern?
Look at almost any brick wall and the bricks overlap: each one sits across the joint between the two bricks below it, half on one and half on the other. Builders call this a bond. Stacking the bricks neatly in straight columns would be quicker and use exactly the same number of bricks.
Why are bricks laid in an overlapping pattern?
The Answer
Overlapping makes the wall act as one piece. A load on one brick is shared by the two beneath it, then by three, then more, fanning out through the wall. And no joint runs straight from top to bottom, so a crack has no easy line to follow.
The mortar between bricks isn't as strong as the bricks themselves. In a wall stacked in columns, the upright joints line up into continuous lines from top to bottom. The wall is really just a row of separate, thin brick towers standing side by side, held together only by mortar. Press hard on one column and it carries the whole load alone; nudge the wall and a crack can run straight down a joint.
Shift each row by half a brick and every upright joint is interrupted by a whole brick above and below it. Weight on one brick spreads sideways into its neighbours as it travels down, so the whole width of the wall shares the load, and a crack has to zigzag its way through bricks and mortar to get anywhere.
There are many patterns of bond. Some, like English bond and Flemish bond, also lay some bricks end-on, so they reach right through the wall and tie its front and back layers together.
The principle: Bonding spreads loads. Overlapping bricks so each one spans a joint below spreads the weight across the wall and leaves no continuous line of weakness for a crack to follow.