Frog
/frog/
Also known as: brick frog, indentation, pressed brick indent
Definition
The indentation or depression formed in the top face of a pressed or moulded brick. When laid frog-up, the void fills with mortar, increasing the bond between brick and bed joint and adding mass. Wire-cut bricks have perforations instead of a frog.
In Practice
Bricks should be laid frog-up to ensure the depression fills with mortar - this improves the mortar bond and the wall's sound insulation and thermal mass. Laying frog-down creates a void which weakens the joint and reduces performance. The frog typically reduces brick weight by around 20%.