Relation: roof строп

You mean PS *stropъ < PIE *ḱrapo- is not possible? Or English roof simply from another root? In entry *hrōfą are listed *krāpo-, *ḱrapo-. And ESSJa mentions English roof for Proto-Slavic *stropъ: "упомянутые герм. слова связываются со слав. *stropъ из и.-е. *ḱrapo-".

I think I see now. I hadn't considered the possibility of a palatovelar. However, the -a- is suspect.