How to get a mono signal for whole house audio

I'm helping my sister plan for whole house audio in the house she's building. I asked the electrician to run 14/4 from the audio equipment to each volume control, then individual runs of 14/2 out to each speaker location. Yesterday I checked his work. He ran a single 14/2 cable from the equipment to the volume control, then a single 14/2 out to a speaker location, then out from there to the next speaker location in series. He wired for MONO instead of stereo! Drywallers are in there today sealing up the house. Bummer! How can I come up with a mono signal to feed this system. A local Guitar Center said I should use a Y connecting cable to combine the left and right preamp outs of the receiver to get mono. Will this work? Any ideas?
Using such a Y-connector would mean that you have mono everywhere. If that is ok with her, you can do it.

OTOH, the electrician is responsible for screwing this up. Whether she wants to make a case of it will depend on how competent this guy was supposed to be and how explicit your instructions were. I wouldn't stand for it. Doing the wiring before the drywall goes up will never be possible again.

If it,s in writing make him do it rite! If it,s verbal would depend on the electricians ethics and honesty. I,d be pissed! Cheers
The instructions were both verbal and in writing. There was also a walk around done showing where to put things with markings on the studs. What possibly could go wrong? It's just stereo wiring-right.
The drywallers started late today and didn't get far. The general contractor and electrician were notified this afternoon of the messed up audio wiring. The electrician was brought back in and made to fix things. He then commenced to mess it up again. The third time it seems he has it right. I've learned that just because someone can wire a house for line voltage doesn't mean they understand stereo wiring. Sad, but true. Thanks for the encouragement to stay after the electrician to get it right.
If he's that bad, I'd want to watch how he runs the wire. Is he pulling it right along with romex/power cables. You may have the worlds worst hum too.

Other note: Does the electrician have a clue on right and left speakers as well as +/-???
Having know a few local custom installers for over twenty five years, I've seen this same scenario more times that I can remember.
Glad to see you stuck with it and hopefully got it all sorted out. I had a new home built a while back. Same problems and then some. I said then that unless I could afford to sit on a lawn chair out front and watch every thing being done to spec, and code I would never do it again. Still alot of qualified and ethical people in the residential construction industry but you never seem to get all of them doing every trade at the same job site. Sorry that nerve ending is still a little exposed! Cheers
His ineptness with a/v is common among electricians. The firm I have been using for years is excellent with electrical issues and very accommodating but puzzled by my demands. A/V issues are simply not part of their training.

It's a bad idea to run stereo recordings in mono because you often will lose music. I'm not talking about soundstage type of stuff.

When you sum stereo recordings to mono there are often phase cancellations, depending upon the care the engineer took in the mixing, so you lose program. (A good engineer may listen in mono to check for phasing issues, but even when detected they are not always easily fixed since they are sometimes the result of improvident mic placement).

You also lose perception of certain elements of a mix. It is common to have a track that is in the same frequency range as another but lower in "volume" and the engineer will therefore separate the tracks spatially so the listener does not lose perception of the quieter track.

Those of you with a mono switch to play with will notice that mono blend sometimes just contracts the sound stage to the center, and other times the music become muddier and you can't hear all the parts you heard in stereo without straining to pick them out.

That's why you read about a recording having a stereo mix and a mono mix. You can't (or at least shouldn't) just sum the stereo mix.