"I have heard it said that Class Five hurricanes can efficiently disassemble a wood frame building in about twenty minutes. According to the New York Times,
That sounds super conservative.
According to Robert Simpson, there are no reasons for a Category 6 on the Saffir–Simpson Scale because it is designed to measure the potential damage of a hurricane to man-made structures. Simpson stated that "...when you get up into winds in excess of 155 mph (249 km/h) you have enough damage if that extreme wind sustains itself for as much as six seconds on a building it's going to cause rupturing damages that are serious no matter how well it's engineered."
That's part of the wikipedia article here: https://en.wikipedia.org/wiki/Saffir
That portion is specifically regarding whether there is any reason for a 6th category to be introduced for truly powerful storms.