When you buy house plans, no matter how complete and detailed they are, you won’t see finished drawings for the electrical work, the plumbing, or the heating and air conditioning. And there are good reasons for this.
Now you will almost always see an electrical schematic plan, showing where switches, outlets and fixtures are (or might be) located, along with a legend explaining all the symbols, but you’ll never see an electrical wiring diagram or any other specific information. This is always supplied by the electrical contractor, not only to satisfy local codes (which vary from state to state across the U.S. and Canada), but also to satisfy the requirements of his or her licensure and liability insurance. Working with the general contractor, the location of the source of the electric power and the main panel will be determined. Distribution is then determined based in part on decisions made by the homeowner.
For example, what the original homeowner wanted in regard to number and location of wall outlets might be very different from what the purchaser of the plans may want. Wiring can also be dependent upon the electrical fixtures (lighting or otherwise) selected, and the homeowner’s desires for internet access. So while a schematic design may be helpful, the electrical subcontractor will always be responsible for the final drawings and installation. And this work is always included in his or her fees.
The same thing goes for the plumbing contractor. I asked an architect long ago why there was no plumbing sheet in his plans. He chuckled before saying “There are only two things a plumber would do with a plumbing detail sheet – he would either throw it away in front of you, or wait until you leave the room.” As I soon learned, plumbing contractors are required to create these detailed drawings, and it’s always included in their fees. Codes vary significantly from state to state, and the location of the source of water can vary as well.
Along with this, once again homeowner decisions will influence the final design. So all the plumber needs from the general contractor are the detailed floor plans, the water source or sources, and the specifications for all the sinks/toilets/showers/etc. the homeowner has selected. And like the electrical sub-contractor, this work is always included in his or her fees.
This is even more of an issue when it comes to plans for HVAC work. First of all, what type of system would you like (forced air, radiant floor heat, etc.)? How would you like to power this system (gas, electricity, solar, etc.). How would you like the house zoned? And finally, there is the climate where you are building to consider.
And by the way, you will never see a materials list in architect-designed plans either. The materials lists offered on stock plan sites are generic ones generated by the software used to draw the plans. They might be of some use in getting estimates (but certainly not bids) from a builder who has not been in business for very long, but they are of no value to him when formulating an actual bid or prior to constructing the house.
Builders get their materials from construction material suppliers, and the suppliers are the ones who create the materials list. Using a set of complete plans, plus their specialized computer software, suppliers determine all of the materials needed, and the costs. It is tailored to suitability in your location/environment, availability, and of course your budget. And it includes everything, not just the board feet of wood needed.