How to do DD on building structure.

[Tom Wang]

Context: I'm looking to move from small multifamily (duplexes, etc) to medium-size low-rise apartment buildings: 10-50 units, 2-3 story buildings.

From my previous experience, I feel fairly confident about what to look for in a regular home inspection. E.g. everything but the structure, which is also the most important.

However, I'm feeling a bit uneasy with buying older buildings (where most of the value assets fall into) without having some knowledge of how to evaluate the structure. Obviously this is not going to be "DIY" but even if I hire a structural engineer, I still want to have a baseline of knowledge (as with any other aspect of RE investing).

Some questions I have in my mind:

-What are the typical structural risks involved with low-rise apartment? I've never heard of a low-rise structure collapsing, but how common is it that a building would be rendered uninhabitable due to structural issues?

-What are the main structural maintenance costs I'd have to do to the structure on an aging building? Say something that is build in the 50's? Would it require retrofitting costs in the 100ks or even millions as time goes on?

-How would one evaluate the structure in a basic walk-through? What are things to look out for? Most buildings I've seen have at least some cracks in the concrete, how do you tell one building has more severe issues than another?

Are there books/classes/other ways to ramp up on this knowledge? How would you go about learning this?