What happens if bricks are laid upside down with the frog facing downward?
- AIt weakens the mortar bond.Correct
- BIt increases the load-bearing capacity.
- CIt improves drainage.
- DIt has no impact.
Solution
Concept
The purpose of the frog in a brick is to hold mortar and create a mechanical key between successive courses of brickwork.
Step-by-step solution
1. Understand the purpose of a brick frog: It is a depression on the top face of a brick meant to receive mortar from the brick above. 2. When laying bricks correctly, the frog faces upward and is filled with mortar. 3. If laid upside down (frog facing downward), the mortar cannot fill the frog, leaving a void. 4. This void significantly reduces the contact area between the mortar and the brick, thus weakening the mortar bond.
Explanation
A frog is a depression provided in a brick to form a key for the mortar. When bricks are laid upside down with the frog facing downward, the mortar cannot fill the depression, resulting in a poor bond and reduced shear strength of the masonry.
Why the other options are wrong
B: Load-bearing capacity decreases, not increases, due to loss of uniform stress transfer. C: Drainage is not a function of a brick's frog. D: It heavily impacts the structural integrity and shear strength of the wall.
Shortcut
Frog always faces UP to hold mortar; facing DOWN means no key and a weak bond.
Common mistake
Thinking the frog is meant for reducing brick weight or improving ventilation.
Correct answer: A) It weakens the mortar bond.