I am laying engineered wood floors to my apartment. I promised the downstairs neighbors to put soundproofing on the floor (I think mostly for impact).
I was planning to put Regupol 3912 which is an acoustic mat (6mm), and put a soundproofing underlay (5mm) on top of the mat. Then, lay the engineered wood flooring. However, Regupol website recommends to put 12mm Tongue & Groove plywood between underlay and engineered wood flooring. My builder is not too keen on doing that. Has anyone used regupol 3912 with engineered wood flooring? Do I really need a layer of T&G plywood stiffener on top of the mat and underlay? I have straight and clean timber underfloor at the moment.