Up or Down?
Some experts say that bricks containing frogs should be laid frog up so that the frog is completely filled with mortar. If the brick is laid frog down, the frog may not be completely filled with mortar. This would render the brick wall face-shell bedded, which gives less wall strength than full mortar bedding.
Other experts say brick should be laid with frog down, for two reasons. First, a uniform bed of mortar can be laid more easily on the face that doesn’t contain the frog. Second, if the frog is laid up, any cavities left can hold water, which may cause frost damage and contribute to early brick deterioration.
Some believe frog down is stronger, resulting in better cement adhesion and a stronger bond between bricks.
Others believe frog up has better strength properties. The load is evenly spread throughout the width of the brick, all the way to its foundations. The debate has raged for generations.