What Does Tie-Rod Hole Mean?
A tie-rod hole is a hole left in a concrete structure after removal of the tie rods used in the concrete formwork. After construction, these holes are typically patched using hydraulic cement or another acceptable material. While tie rod holes do not significantly affect the overall strength of the finished concrete structure, they are known to be the cause of leaks, particularly in foundations or basement walls.
Corrosionpedia Explains Tie-Rod Hole
Tie rods are temporary structures. Their primary function is to secure the formwork by holding them together during concrete pouring operations. They do this by clamping the formwork, preventing either side from bulging under the wet weight of the concrete.
As the concrete is poured, it flows over and around the tie rod, thus leaving a hole when the concrete has cured and the rods are removed. While these holes are typically patched after the rod's removal, ground movement and freeze/thaw cycles can cause the patching work to break down over time.
This can be a problem in foundation walls, where groundwater can make its way through the void and into basements.