On large jobs we have been given detailed plans, showing where each cable runs and where every box is placed, these are often altered and after you get an asbuilt showing how it was finally wired. This is because many firms and many trades working together, so you don't want wiring to get in the way of steam pipes which are going in latter, and often tray work is laid by completely different firm to one laying cables, and they are connected by again another firm, so they have no real option but to make detailed plans.
In the main a home is much simpler, yes needs some design, will sockets be split up/down, side/side, front/back same with lights, and there will be some separation between low and extra low voltage and the plumbing. With a new build as with larger commercial premises there will be designated routes, so wires not in the way of pipes etc. But on a re-wire it is more down to where one can get assess to, and what re-decoration will be required, so one wall papered and three walls painted, putting sockets on painted walls makes filling and re-decoration cheaper and easier. If wires don't need to cross beams then again cheaper, and in the main it is a compromise.
So my instructions to firm rewiring mothers house, location of TV etc and sockets required, all sockets to be flush and all sockets on the ring so more can be added latter, trunking allowed in the corners of a room where already installed, but no trunking away from corners, still found one cable in horizontal trunking across wall. But instructions were vague as wanted cheap job, so if sockets could be back to back clearly a saving both materials and making good latter.
All redundant sockets to be removed, again they did not do that, found some dead sockets, due to panelling on stairs agreed hall and landing light positioned so they would light stairs and second light to spread the light along them, they did it on landing, not on hall. My main problem was speed, it was costing £500 a week to have mother in a home while it was being done, so I agreed to some changes to speed it all up.
It is all well and good saying I want a socket on that wall there, but it should also conform with the Parts of the building regulations, it was pointed out with my mother she was in a wheel chair so the distances given in Part M as to locations for wheel chair uses needed following, how far from corner, and how far up the wall, with some specials like two way switch for bedroom lights and thermostat low enough so she could see it.
And clearly not being occupied while being rewired does reduce price and make it safer, but once the electrician has started it is likely some changes will be required, be it pipes in the way, or plaster blown so want to avoid that wall. In the main there needs to be trust and give and take.
I remember working for one guy, and we had given a quote for the work, while doing the work the lady of the house would ask can you do this, or can you do that, and answer was invariable yes, at end of the job the bill was sent to the guy, £x for agreed work on quote plus £x for the extras requested by Mrs xyz. I felt it was sneaky, but was not my call, but learnt from it, so have been careful to ask will I be charged for this. So trust is important, not just cheapest quote.
