noun, feminine/lɑ̃.buʁd/plural: lambourdes
joist
“Il n'était pas achevé d'être bâti, et l'on voyait le ciel à travers les lambourdes de la toiture.” — The building was unfinished; the sky could be seen through the joists of the roofing.
Inherited from Old French laon (“plank”) and bourde (“beam”).