From 藁(わら) (wara, “straw”) + 葺(ふ)き (fuki, 連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 葺(ふ)く (fuku, “to thatch”)).
藁(わら)葺(ぶ)き • (warabuki)