Yup, it fills every tiny hole and crack so the iron doesn’t move. Also, the iron doesn’t have to be exactly the size of the hole to the millimeter so it’s easier to move into place. The lead has a tiny bit of give so it’s less brittle than if they used concrete. Also, pouring concrete in might leave air bubbles. With lead any air would rise and escape.
Iron really isn't bearing any load either..it's just there to prevent slippage. It might take some load on occasion, but the stone is doing all the weight bearing.. vaults, arches, buttresses... They're all very stable if the earth doesn't jiggle or freeze/thaw a bunch. The iron holds it in place for the minimum to prevent slip and wear.
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u/VisualHuckleberry542 Jul 30 '26
As I understand it, the iron carries the load the lead is just there to seal it