He has another

The plywood option takes less than. He has another plus — the floor will be a little warmer due to the resulting wooden layer. But we must understand that plywood will hide only minor irregularities. If the concrete slab is initially “a wave” (it happens) a wooden sheet will begin to swing on this “wave” like on a swing — the floor will walk and creak. So with strong bumps, you still have to make a screed.