building bridges

How do you join the old sagging slanted antique floor to the new level straight floor? A pertinent question, especially when you're creating an open plan area. You simply start knocking things out with a pneumatic hammer to strip three layers of flooring. You leave the wattling and daubing that is still attached to the many layers of ceilings below (now the wine-shop). You remove 300 year-old oak joisting. You do all this when the wife is at work. When she comes home, you explain there are now bridges to walk on between kitchen and living areas. You justify the thick layers of fine dust covering the new kitchen by explaining it was the only way to go. You do want a strong base for your hardwood floor, don't you?