For Framing ,roofing , building, any major electricity and plumbing I usually contract out. Reason is, their work is waranteed and covered by insurance. I had a 5000 sq ft building (in 2 floors, designed and built as a farm outbuilding and office and studio for Ms F and me and it was built on a footprint of an arlier building that was gtting seedy. The concrete footprint was expanded, and the whole thing was done by an AMish Contractor in less than 3 months (In the winter). They painted an did finished carpentry in the spring. AND, Weve been perfectly happy with it for 4 years.The builder subbed out the electricity ad wifi and plumbers did the in and out (it adjoins a 10 acre paddock area)
I know a guy who was always doing his own plumbing and because our water is acidic and "country style", hed always have a mess with grit and pH doing damage. They make gizmos to deal with that an the contractors use their own experts when they need tech help..