I wouldn’t be so categorical, I’m afraid. It depends on the cause of subsidence. For example, subsidence caused by tree roots would not be defective design/workmanship/materials of the foundations etc. May result in s.11 L&T 1985 disrepair, but not be a s.125 issue. Similarly, what if the subsidence is not so severe as to threaten destruction, closure etc. Unless you can bring it under (c)(ii) physical damage to the building, it will not be a s.125 issue.

So I can’t agree that subsidence per se is a structural defect for the purposes of s.125, though it certainly could be.

(a) results in, or is likely to result in, the building or any part of the building being required by or under any law to be closed or prohibited from being used, or
(b) prevents, or is likely to prevent, the continued practical use of the building or any part of the building, or
(c) results in, or is likely to result in:
(i) the destruction of the building or any part of the building, or
(ii) physical damage to the building or any part of the building, or
(d) results in, or is likely to result in, a threat of imminent collapse that may reasonably be considered to cause destruction of the building or physical damage to the building or any part of the building.

*”structural element of a building” means:
(a) any internal or external load-bearing component of the building that is essential to the stability of the building or any part of it, including things such as foundations, floors, walls, roofs, columns and beams, and
(b) any component (including weatherproofing) that forms part of the external walls or roof of the building.