exteriors can generally be done with 90mm. In tighter urban areas a 75mm is often good. Some times only the very widest will work, but not often.
Interiors are often in the 65mm -90mm range with the shorter end being used more often, but again sometimes you will need to go wider (seldom longer).
A serious Arch photog will have:
47mm and or 58mm, 65mm and or 72mm/75mm, 90mm, 110mm, 135mm and or 150mm and possibly a 210mm.
Most of the time 65mm - 90mm are what will be used.
Pick up Interior design mags, Arch mags and realeastate mags to see what is being used.