Yellow stuff inside PVC windows.

virginblue4 · 12 March at 5:27PM

Hi all, I’ve just noticed that the internal window boards and reveals seem to be stained with yellow splashes. Looking closer, there seems to be some yellow stuff coming out of a small crack and maybe that’s what has been seeping down. What on earth is it? Is it some sort of mould, or maybe water penetration mixing with some sort of hidden rust? There is a concrete lintel above the window.