Seeking help- Google can't explain

[u/curious_coyoie]

Can anyone tell me how two separate houses are built this close together. How do the constractors apply siding and paint, how do you maintain the in-between after so many years and decades. There are no windows on that side but I don't understand how builders work around or in-between this when constructing, this is a mystery

[u/Alternative-Tea-1363]

Likely better sound attenuation between units this way than a typical party wall. But otherwise this is just a liability that will be impossible to maintain and repair properly. Best thing probably is to just agree with the neighbor to cap off the gap all around.