Crawl spaces
Should I build on a slab on grade foundation or a crawl space?
...foundations to meet building code in most regions (we hope), but putting plumbing lines in conduits is also a good idea; that way, if for any reason at all you need to replace a waterline, you simply pull the PEX out of the conduit and replace it.
An additional feature I once saw that made a lot of sense was a second b...