- Strength: Horse hair adds strength and reinforcement to mortar, making it more resistant to cracking and wear. The hair fibers act as tiny bridges that help hold the mortar together, preventing it from becoming brittle and breaking.
- Flexibility: Horse hair provides flexibility to mortar, making it less prone to cracking due to temperature changes or movement of the substrate. The hair fibers allow the mortar to expand and contract slightly, reducing the risk of cracking.
- Bonding: Horse hair helps improve the bond between the mortar and the masonry units (bricks, stones, etc.). The hair fibers mechanically interlock with the rough surfaces of the masonry, creating a stronger bond and preventing delamination.
- Water resistance: Horse hair can enhance the water resistance of mortar. The hair fibers absorb water and swell, forming a tight network that reduces water penetration and helps protect the masonry structure from moisture damage.
Traditionally, horse hair was mixed with mortar by hand, but nowadays, synthetic fibers such as polypropylene fibers are commonly used as an alternative due to their similar properties and ease of use.