Full hazmat attire with watertight work boots.

Tough, water tight, easy to stack...Seems like an ideal way to create a neat place.

It's getting to be about time to add more urethane.Regarding carpet, I buy the best quality for the money that I can find when I need it and then I glue it down real good so it becomes almost watertight.

Foundations of that era were not meant to be water tight.

Address the leak immediately, once the house is water tight get everything dry and then you can approach the cosmetic repairs over time. 

You can then be pleasantly surprised if you find a solid subfloor, watertight roof, or salvageable drywall.

As an old civil engineer I’m not confident that all those penetrations through shingles and membrane would stay water tight.  

Specifically,- Is older basement water tight or needs French drains and sump pump installed?

You may find that the sealant is loose and is not watertight.

For LVP only ever use glue down, it's the only way to get maximum benefits and assure water tight.