What is the purpose of expansion joints in building construction?

Expansion joints are crucial components in building construction, designed specifically to accommodate the movement of materials caused by temperature fluctuations. When temperatures rise, building materials such as concrete and steel tend to expand, while at lower temperatures, they contract. This cyclical movement can lead to cracks or structural damage if not properly managed.

By incorporating expansion joints into building designs, engineers ensure that there is a designated space for this movement, allowing materials to shift without causing stress or damage to the surrounding structures. This not only prolongs the lifespan of the building materials but also maintains the structural integrity of the entire construction.

The other options do have their own purposes in construction, such as controlling water flow or enhancing structural strength, but they do not specifically address the movement related to thermal expansion and contraction as effectively as expansion joints do.