請教 mold 問題：(自住房)

建自住房, 發現wood framing中有十多根 mold 嚴重。工人 sand 處理了，工程繼續進行。幾天後， mold 又生長了。 請問應如何處理方能清除徹底？Online search found bleach actually doesn't work for wood. Should we request builder to hire mold cleaning company? In general, is it a serious problem if molded framing exists in a house?