Irma: Gusts of 225 MPH!

[defacto7]

68. Here's a couple of links

The first covers tornadoes and has some fair examples and explanation of the damage calculation. The second is hurricane damage and it seems to follow similar damage distinctions although there's some critique about the scale. 5 in either case is "catastrophic damage will occur" then it explains what that is.
There isn't a higher level because the expected damage would be the same under a standard condition. You can't expect to calculate damage evenly in all cases because there are too many random variables in structures, gusts, saturation, foundations, flying debris, etc. The scales try to give some measure of understanding to a random event using common structures, materials, trees and plants. A simple example would be that a concrete shead on a concrete foundation on stone may withstand a strong F5 yet a another one on sand would collapse in an F1. Yet the first example would still be standing even if the windspeed was 300mph.
Predicting damage in a storm is very general but it gives enough info to warn you of the danger. Wind 156 mph.. get out now. Wind 900 mph.. get out now.

http://www.spc.noaa.gov/faq/tornado/ef-scale.html

https://en.m.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale