Electrical in 50 year old house - what to do

15 Replies

I am rehabbing this 1st property.  Part of closing negotiations was that they replace the breaker box.  They hired a professional electrician who installed a 125 amp breaker box.  It looks like they did a very good job - I'm no electrician, but it looks better than the previous.

Most outlets/switches are 2 wire.  What do you guys recommend I do at this stage? 

I found this information on Homelectrical

The Consumer Product Safety Commission (CPSC) only recommends the following three methods to fix aluminum wire problems permanently

  1. Completely replace your home with copper wire
  2. Pigtail the aluminum wire ends with special crimp connectors called COPALUM
  3. Connect the aluminum wire ends with aluminum to copper AlumiConn wire lug connector

Any other ideas from the pros??? I am hoping you don't say rewire... Is there a maybe a staged approach?

2nd post - You guys gave a LOT of good feedback on the insulation / vapor barrier post - Thanks a LOT.

@Troy Welch

Do you have aluminum wiring? Or are you guessing?

Aluminum wiring was only used for a short period of time between 1960 and 1975 due to copper prices at the time.

If you do, and you're going to rehab the house, this is the best time to do it.

If you have two prong outlets, they can be replaced with three prong. If they used metal boxes, the three prong automatically ground to the boxes. If they have plastic boxes, then you just need a grounding wire. If the wiring was never replaced, it's doubtful you have plastic boxes. You can get the outlets for about a $1 each.

Actually to do a complete rewire job is the easiest to accomplish of all your options. I am a journeyman electrician as well as a previously licensed electrical contractor with a work force of over 100 electircians working for me, but the past is the past. However especially when you are talking about Aluminum wiring you really do want to repace is all with modern copper cable that has a ground wire in the cable. I will explain my reasons why. Althuogh coductive aluminum wire has a lot of resistance and that lead to the wires getting hot. An awful lot of houses catch fire because of hot aluminum wiring. Pig tails of no pig tails at splices and electrical components. The thing about heat is that it easily transfer and heat damage is permanent, no way to undo it. A typical Do it yourself book you can buy at Home Depot, Lowes and the like should suffice to guide you. There are a few ways to improve you entire electrical system installations without rewiring but I am not going to go into that because simply I would not recommend it. Maybe that may come across as not being investor friendly but I have just come across too many failures and houses on fire to have a different opinion about it.

That's like asking your doctor of many years experience about heart problems you've been having and saying, " Please do not recommend heart surgery even if my life depends on it".

Christopher / Gilbert

Thanks for your feedback. I found some humor in the comment

"That's like asking your doctor of many years experience about heart problems you've been having and saying, " Please do not recommend heart surgery even if my life depends on it"."

Originally posted by @Troy Welch :

Christopher / Gilbert

Thanks for your feedback. I found some humor in the comment

"That's like asking your doctor of many years experience about heart problems you've been having and saying, " Please do not recommend heart surgery even if my life depends on it"."

 I agree with the other guys. Rewire. Electrical needs have changed over the years and you can add some outlets and lights where they didn't exist before.

This (and plumbing) are the areas I always have permits for and have inspections done. Let the inspector find the mistakes, it won't hurt you. And, in the future if there is a fire or flood, when the lawyers start circling like vultures, you will have a better chance of staying out of the mix.

As far as rewiring difficulty a lot depends on the configuration of the house, If you have a basement and attic it can be easy. I've found that some electricians (not all) want to make lots of holes and rip out out walls becaue it's easy on them. If you're doing it yourself and can take your time fishing new wire can be done with a minimum of wall work, often just one hole to cut a slot in the cat. My houses all have old AC cable, my rule has been if it's ancient fabric coated it goes if at all possible, newer vinyl coated can stay.

Account Closed I don't know where the OP is, but in NJ the owner cannot pull a DIY permit for a non owner-occupied home or a multifamily. It's either get an electrician or do it on the down-low. I understand all the reasons for this, good and bad, but IMO it makes for a lot of uninspected work being done. From what I've seen our inspectors don't really look very much, so more DIY permits would mean they would actually have to do their jobs.

Disclaimer: I am not a professional electrician.

Also, wall of text incoming.  :)

As has been said, do you know you have any aluminum wiring?  And, did the person who told you that actually look, or were they guessing based on the age of the house?  In general, two-wire (without ground) cable and aluminum wiring didn't really overlap in time, when houses were being built.  If somebody did an addition or renovation later, you might have aluminum wiring.

If you don't mind taking the cover of the breaker panel off, you can check in there for aluminum wiring.  CAUTION: There are things in there that are always live, even if all the breakers are off.  Don't do this if you don't know what to stay away from.  You're looking for the bare metal part of the wire, not the insulation - if it's silver-colored, it's aluminum.  If you have aluminum wiring on any of the normal branch circuits - the 15 or 20 amp circuits to the light fixtures, receptacles, etc - it should probably be replaced.

If you don't want to open up the breaker panel, you can check some of the outlets and switches around the house relatively safely.  Turn off the breaker first, and flick the switch or try a lamp (that you know works) in the outlet to be sure it's really off.  Then take the switch or outlet out of the box and look.  If there is an addition, or a part of the house that was finished later (finished basement or attic?), make sure you look at the wiring in that part of the house.

It is not such a disaster if the cables to the electric range or electric dryer are aluminum.  These usually only have two connections - one at the breaker box and one at the outlet for the appliance - so they don't usually have the problem of a daisy-chain of bad connections all over the house.  If it were me, I'd turn off the breaker, disassemble the outlets at the appliance, and inspect for scorch marks, melted plastic, etc.  If the damage was on the receptacle, I'd get a new receptacle, but if it looked like the wiring was damaged, I would think real hard about rewiring that circuit with copper.

If you have an electric furnace or electric air conditioner with aluminum wiring to them, those may take a little more work.  An electric furnace usually has set-screw connections, which is OK-ish, as long as they were rated for aluminum wire - it's probably a good idea to take the furnace cover off and look.  There should be a label somewhere near the connectors, or on the main nameplate label, that says if the terminals are suitable for aluminum.  An electric air conditioner often connects with wire nuts, which aren't such a great idea on aluminum - you either need wire nuts that are made for aluminum, or to get an electrician to install a crimp connector instead of the wire nuts.

Okay.  Assuming you don't have any aluminum wires...

Depending on how excited your area (city, county, state) is about permits and inspections, they may have some ideas on what standard you need to bring things up to.  It may be worth talking to them.  The rules vary - sometimes you only have to meet the electrical code for the year that the house was built; sometimes all the new work has to meet modern code, but the old work can be left in place - sometimes you have to upgrade everything.  The local inspections department will know for sure.

It's probably worthwhile to check the outlets to see which ones have ground and which don't.  If the house is before approximately 1955, probably nothing is grounded.  From about 1955 until about the mid-late 1960s, you might have grounded kitchen, laundry, and maybe bathroom outlets, but nothing else.  Past about 1970, usually everything is grounded.  Just because there's a three-prong outlet doesn't mean it's grounded.  What happens is that a two-prong outlet wears out and cracks, and so the owner goes to the hardware store.  New two-prong outlets are $3 and new three-prong outlets are $0.50, so they buy and install the cheap one and just don't hook up the ground.

The way to tell is with one of those "three neon lights on a plug" testers from the hardware store.  I have the $5 one without a GFCI test button; you might splurge on the $8 one with the GFCI button.  Also get one of those adapters that screws into a lamp socket and gives you a two-prong outlet, and a 3 prong-2 prong adapter.  Try the tester at your house, or somewhere you know that has working grounded outlets, to see what the lights look like.  Plug the tester into the 3-2 adapter and then into the wall at your house, to see what that looks like, and then plug the tester into the 3-2, the 3-2 into the lamp socket adapter, and screw the whole schmutz into a lamp socket, to see what that looks like.  (One of the lights will never be on when you test a lamp socket, since there isn't a ground.  If you're testing a ceiling fixture, grab a short piece of any kind of insulated wire, strip each end back a half inch, and touch one bare end of the wire to the tab on the 3-2 adapter and the other bare end to one of the screws that holds the fixture to the ceiling box.  If the box is grounded, that will make the second light on the tester come on.)  Then take all your toys to the rent house and have fun.  Put a Post-it note or maybe a piece of masking tape on the wall or floor near each thing you test with a note.

While you're testing, also note if the 3-2 adapter is "too easy" to plug in to any of the outlets - in other words, see if the contacts in the outlet are worn out.  It's better to use a 2-prong plug for these tests, even on a 3-prong outlet - most things only have 2 prongs, and using a plug with a ground prong for this test can make an outlet feel OK even when it isn't.  If you're not sure what it's supposed to feel like, plug a new plug into a new receptacle at the hardware store.  Outlets that have been in use for a little while may not be quite as stiff as a brand-new one, but the plug shouldn't just fall out of the outlet, either.

1.  If you do have some outlets without grounds, the cheapest thing to do is probably to install a GFCI in the first outlet on each circuit.  This provides some extra protection to those circuits, without rewiring them completely.  If you find any 3-prong outlets without grounds, or a 2-prong outlet that's worn out, replace them with new 2-prong outlets.

If you can't figure out which outlet is first on the circuit, or if the circuit is a pain in the butt in some other way, you can also get a GFCI built into a circuit breaker that can be installed in the panel.  However, the GFCI breakers are about $60, whereas the GFCI outlets are about $15.

You also have to think about whether you want to install a GFCI for things like a refrigerator or freezer, such that if the GFCI trips, somebody might not notice for a while.

If I was doing this, I'd also go around to the 2-wire outlets I was keeping and see if any of them were "back-wired" or "stabbed" or "back-stabbed", and if they were, I'd move the connections to the screw terminals instead - cut off the bare end of the wire, strip the insulation some more, loop it around the screw, tighten.  Some outlets just let you poke the wire in the back, where it is retained by a spring clip.  These connections inevitably loosen up over time - sometimes you can pull the wire out of the outlet by hand!  This can lead to heat and FIRE at that connection.  (The screw terminals don't loosen up.)

Another way you can test the regular outlets involves a voltmeter and either a small space heater or a hair dryer.  The voltmeter can be any digital voltmeter that will read 120 V AC.  It helps to get a 2-prong plug with some cord on it (cut it off of a dead appliance), strip the ends of each wire a half-inch or so, wrap each wire around one test prod, and then tape it up really good with electrical tape - that way you don't need three hands for the next part.  Or, if your meter leads unplug at both ends, get a replacement set of leads, cut off the test prods, and wire the red and black wires directly to a 2-prong plug.  If you like gadgets, get a "Kill-a-watt" or similar plug-in meter online, or at some hardware stores, for about $30.

Go to an outlet, plug in your meter, and write down the reading.  It's normal for it not to be exactly 120.0 V AC, and it's normal for it to bounce around a few tenths of a volt while you watch it.  If it's consistently way low (below maybe 110.0 V) or way high (above maybe 125.0 V), you may want to seek help from an electrician before proceeding.  Now, plug in the space heater or hair dryer, and crank it up to high.  Watch the voltmeter while you do this.  It is totally normal for the voltage to drop down when the heater/dryer kicks in, but let the heater/dryer run for a couple of minutes and write down the lowest voltage you see.  Then, turn the heater/dryer off and do some math.  If the voltage dropped 5% or less (like, it was 120.0 V with the heater off, and 114.0 V at its lowest with the heater on), then the circuit from the breaker panel to that outlet is in pretty good shape.  If it's between 5% and maybe 8%, that's not as good, but it might be OK.  If it's over 10%, then you should investigate further, or have an electrician investigate - you've got a loose connection somewhere between that outlet and the breaker box, which is potentially dissipating a lot of heat inside the wall somewhere.  Back-stabbed connections, loose wire nuts, and terminal screws that aren't tightened all the way down on receptacles and switches can cause this problem.

2.  The next step up used to be that you could run a separate ground wire from something you knew was grounded (the breaker panel, or a metal water pipe (NOT THE GAS PIPE) coming from the street, or a ground rod) to the outlets that didn't have them, and then install 3-wire outlets.  This has since been removed from the electrical code.  Your local area may or may not let you do this.

3.  The next step up from that is to rewire with 3-wire cable and 3-prong outlets everywhere.  This can be uncheap, but then you don't have to worry about it anymore.

If you do this, you're probably hiring an electrician.  Ask them to use the "spec grade" receptacles and switches - the ones that cost about $1 each at the hardware store, rather than $0.50.  They will also have "spec grade" stamped into the metal mounting strap.  In a 1,000 square foot 3 bed/1 bath house, using the cheap receptacles and switches will cost about $30, and using the spec-grade ones will cost about $60.  Since you're usually looking at a couple of thousand dollars for a rewire, the cost difference is minimal.  The spec grade stuff lasts longer before wearing out.

If you do this, you might also ask the electrician to install wired smoke detectors.  (Your local area may even mandate this.)  It's pretty easy for them to do while they're already wiring everything else, and in my opinion, it's safer for the tenants - even if the smoke detector batteries are missing for some reason, the detectors still have a chance at working.

Like @Johann Jells said, if there is access in the basement and attic, the rewire gets a little easier.  If the attic is unfinished, you might think about getting some 1"x12" (or so) boards, or ripping a 4'x8' sheet of plywood into four 8'x12" boards, and putting those across the rafters down the middle of the attic.  Shoot a couple of screws through the boards into the rafters so nobody does a Laurel and Hardy step-on-the-rake move.  Leave one 1x12 loose up in the attic so the electrician can put it where they need it.  If there aren't lights or windows up there, maybe get a couple of cheap used 4' shop light fixtures from the ReStore, hang them in the attic, and plug them into an extension cord that goes downstairs.  All of this reduces the chances that you find a work boot dangling from a new hole in the ceiling during the job.  :)  Sometimes in the basement, it helps to temporarily remove a built-in shelf, or move the washer and dryer - stuff like that.  Ask the electrician when they are there to give you the estimate.  Don't pull out any of the existing wiring on your own, though - sometimes they can use the old wire to pull in the new, and they can at least use the same holes for the new wire.

(If your area requires you to bring the house up to very recent code, they may also require a thing called an AFCI on some of the circuits.  At first, you could only get AFCIs as breakers, but I think you can also get them as outlets now.  The purpose of an AFCI is to make money for their manufacturers, IMHO.  If we actually wanted to fix the problem that AFCIs are supposed to solve, we'd put fuses in all the plugs, like the UK.  Regulatory capture is a thing, though.)

Is that far more than you wanted to know about it?  :D

I don't get money from any companies mentioned.

Matt R.

MOST electricians don't like fishing old houses to rewire them.  Mine said 6 to 10K to rewire a small house.  HE said there is no rule for fishing the wires only.  In other words you could fish wires and have an electrician connect the breaker box and outlets/switches.  He will be happy and you to with his bill (MUCH lower)

IF you have aluminum wire I would take it ALL out somehow.  Same with knob and tube wiring.  IF your insurance company gets a whiff of either you will be looking for a new company.

Another major thing to inspect is if you have a Federal Pacific breaker box.  First clue is if a new breaker costs 60 bucks or more.  Normal breakers cost 3-8 bucks for non gfic types.  Anyway there were tons of these FP boxes used in the 70's and earlier and breakers don't trip when the NEED to trip causing fires.

In our area we don't see much aluminum wire in houses but mobile homes were loaded with them.  Their was a lot of cloth wire type tho.  IF you look and see very thin wires even if copper they can cause problems when electric space heaters are used.  OLD wiring in houses were designed for 40 watt bulb and two of thiose.  Not all the electric stuff we have now.

If your wiring is modern but just 2 wire it is easy to put a  double outlet of 3 wire where any Susie Homemaker can easy plug in using NEW 12 ga. wire on a heavier breaker and 3 prong outlets.  Lets say Suzie wants to plug her 3 prong vac  cord into the wall to do her vacuuming .  Is she going to plug into the new wire circuit or climb behind the heavy furniture and fumble with an adapter to plug into the 2 prong.  Same applies to a dreaded landlord item called a 'space' heater.  Those boxes that cause more winter fires especially on an extension cord cause outlets are all hidden .  Leases should prohibit space heaters if wiring is old.  But wont Suzie plug into the easiest outlet out in the open?  So put more outlets where they can get to them and those will be most used.  I

Most breaker  boxes are too small.  If your putting in a new one put a 200 amp box in.  Doesn't cost much more and has tons more spaces, which is always short.  In 50 years what will needs be?

Originally posted by @Don Meinke :
Another major thing to inspect is if you have a Federal Pacific breaker box.  First clue is if a new breaker costs 60 bucks or more.  Normal breakers cost 3-8 bucks for non gfic types.  Anyway there were tons of these FP boxes used in the 70's and earlier and breakers don't trip when the NEED to trip causing fires.

This is a good point.  Zinsco is another brand of panel to watch out for.  Besides the price clue Don mentioned, the other way to tell is whether or not you can still get breakers from the original manufacturer.  Walk into any big-box store and you can buy GE, Square D, and Cutler-Hammer breakers that are actually made by GE, Square D, and Cutler-Hammer.  The breakers to fit FPE and Zinsco panels will be sold by "Acme Breakers" or something like that.

Most breaker boxes are too small. If your putting in a new one put a 200 amp box in. Doesn't cost much more and has tons more spaces, which is always short. In 50 years what will needs be?

I agree with this too, but note that you don't have to upgrade the service from the electric utility to do this.  (You can upgrade it if you want to, but it's uncheap, and in town the utility will often insist on you hiring an electrician to make the cutover.)  You can buy the bigger panel, change out the main breaker to match what your service is, and then enjoy all the extra spaces in the panel.

Thank you Matt R for your seconding of the major points of what I was saying.

I forgot the other main reason I like a 200 amp box and service.  "IF" you or anyone wants to put a tankless electric water heater in that is about as small of service that will allow it.  I think I remember that it takes 3 legs of XXX amount of amps to power them up.

The importance of this is sometimes no chimney avail for a regular gas and a flue less don't work for what ever reason like too far of run to outside, ascetic's, or utility bill paid by tenant OR just space concerns.

Guys, this is some great feedback. 

The breaker box was replaced in August this year right before I took ownership. The electrician replaced the old 100 amp breaker with a 125 amp breaker. I wanted them to just provide an allowance so I could go with a 200 amp breaker but couldn't come to terms on it. So I am satisfied with the 125 amp breaker.

I have talked to someone from the company that did the work. At the time, I wasn't aware of the possibility of aluminum, we just talked about grounding or lack of. The person I spoke to suggested installing GFCI's on the first outlet of each circuit. If I don't have aluminum wiring, I will probably go this route this time, then replace wiring on the next upgrade. My only concern is the renter tripping GFCI's and calling every time - I guess it is easy enough to just tell them to reset.

I am handy enough to do the GFCI replacements - when I was a teenager, I volunteered on projects thru my religious organization in the electrical department. I've installed switches, receptacles, light fixtures, ran conduit, pulled wire. I never really got near the breaker panel on those projects. I've also installed several ceiling fans including one in the rent house and an led porch light.

I also like the idea of running the cables myself and letting the electrician connect to the breaker box. I am assuming that each room gets a run from the breaker box that splits to switch/light and receptacles that are in series, right? I should be able to talk with guy at the big box store for cable size and the like. Each room is pretty simple:

Living - 1 ceiling fan/light on common switch, 1 switch to porch light, 1 receptacle on each wall

Each of 3 bedrooms - 1 ceiling fan/light on common switch, 1 receptacle on 3 of 4 walls

Bathroom - 1 switch for vanity lights, 1 switch for exhaust fan/light (I am going to daisy chain an led light for more light in shower), 2 GFCI's

Hallway - 2 switches - one operates a light, the other used to operate an attic fan which is now removed

Kitchen - probably the most complicated 2 lights operated by single pole switches, currently 9 receptacles - 2 general purpose, 3 counter height, 1 for dishwasher, 1 for refrigerator, 1 for cooktop, 1 for oven. I will be going back with a range instead of cooktop/oven. A good point was made about no GFCI on refrigerator.

Garage - 3 switches -1 for garage, 1 for back yard flood light, 1 labeled as "goes to nothin", 1 GFCI that isn't working, 1 receptacle for washer dryer 

Updated over 2 years ago

The house is a single story on a foundation. Based on my DEMO in the kitchen, there is no insulation in the exterior kitchen walls. Also, since they had an attic fan at one time, I would assume none of the exterior walls are insulated.

Originally posted by @Christopher Phillips :

@Troy Welch

Do you have aluminum wiring? Or are you guessing?

Aluminum wiring was only used for a short period of time between 1960 and 1975 due to copper prices at the time.

If you do, and you're going to rehab the house, this is the best time to do it.

If you have two prong outlets, they can be replaced with three prong. If they used metal boxes, the three prong automatically ground to the boxes. If they have plastic boxes, then you just need a grounding wire. If the wiring was never replaced, it's doubtful you have plastic boxes. You can get the outlets for about a $1 each.

The house was built in 68. I have not confirmed whether or no aluminum wiring was used. I will open the panel next weekend when I am there to see if i can confirm. I will also talk to the company who replaced the panel to see if they remember - this was done in August. 

I think most of the boxes are original metal. I didn't realize that grounding to the box is acceptable.

@Troy Welch

Outlets just need to be grounded in order to have three prong. Either to the outlet metal box if BX flexible metal conduit cable was used, or a grounding wire has to be used if a plastic box and Romex plastic covered wiring is there.

Romex wasn't originally up to code in many states, but now many allow it. So, I often go into homes and see all kinds of old and new things mixed together.

So, you might have some BX used and then newer work using Romex.

Sometimes people cover up the electrical panel and you can't tell what's going on. Other times, especially with an unfinished basement, it's easy to see what was used.

One issue we ran into remodeling a house significantly older than yours was knob and tube. At some point romex was run from the breaker box into the attic,  and from the receptacles to the attic, so if you looked at either  end it appeared like all the wiring was new. But running through the attic, connecting that nice new wiring was very old knob and tube.

You just have to wonder about people who do things like that. They did the hard part -- getting the new wire in the walls -- so it had to be an attempt to save money. 

"Oooh I know how we can save 2 bucks and set ourselves up for a potential electrical fire!"

Originally posted by @Troy Welch :

I am rehabbing this 1st property.  Part of closing negotiations was that they replace the breaker box.  They hired a professional electrician who installed a 125 amp breaker box.  It looks like they did a very good job - I'm no electrician, but it looks better than the previous.

Most outlets/switches are 2 wire.  What do you guys recommend I do at this stage? 

I found this information on Homelectrical

The Consumer Product Safety Commission (CPSC) only recommends the following three methods to fix aluminum wire problems permanently

  1. Completely replace your home with copper wire
  2. Pigtail the aluminum wire ends with special crimp connectors called COPALUM
  3. Connect the aluminum wire ends with aluminum to copper AlumiConn wire lug connector

Any other ideas from the pros??? I am hoping you don't say rewire... Is there a maybe a staged approach?

2nd post - You guys gave a LOT of good feedback on the insulation / vapor barrier post - Thanks a LOT.

If you have no ground I will assume the wire is as old as the house. Its probably 2 wire romex but just in case look up in the attic and see if you see knobs and tubes with wire running in them. If it does and it is hot you will need to take it out. That is worse than having  aluminum wiring. Do you have the old breaker box? What brand of breaker was in them? 

You can put a junction box in the attic and umbrella down to your plugs before you install your insulation. Get an oscillating cutter tool and cut your boxes and use "pop in" boxes. Spend a little on the fiberglass fishing rod and its doable. I would recommend you use an electrician though. 

@Troy Welch

The electrician replaced the old 100 amp breaker with a 125 amp breaker. I wanted them to just provide an allowance so I could go with a 200 amp breaker but couldn't come to terms on it. So I am satisfied with the 125 amp breaker.

The reason why they wouldn't "just" install a bigger main breaker / panel is that the transformer in the back yard (on a pole or on the ground), the wires from the transformer to the meter, and the wires from the meter to the panel all have to be sized for the size of the service. This gets into what the electric utility will let you do. I can see them saying that installing a 125 A main breaker on a service that was originally sized and wired for 100 A is OK, especially if the utility knows they've upgraded their transformers since 1968. Going to a 200 A (or more) main breaker probably means they want you to replace the wires from the pole to the meter, the meter socket, and the wires from the meter to the breaker panel, which drives up the cost. It might also mean that they'd have to install a bigger transformer, and they want to subtract part of the cost of the new transformer from you. (Electricity is a little weird... usually you own the wires all the way out to the pole, so fixing or upgrading them is your baby. You don't own the electricity itself until it goes through the meter, though.)

My only concern is the renter tripping GFCI's and calling every time - I guess it is easy enough to just tell them to reset.

I don't yet know for sure if it helps or not, but I gave my tenants a 3-ring binder with copies of all the appliance manuals in it. There are also a couple of pages at the beginning about the GFCI outlets, how to reset them, and which sockets each one controls. For something like the bathroom, it's simple - the GFCI will be the only socket on that circuit, so if you pop it, you will be standing right in front of it. However, it might not be obvious to the tenant that if they plug in something in the bedroom and that outlet stops working, then they need to go reset the GFCI in the living room. (A lot of GFCIs now have a small LED on them that's only on when the GFCI is not tripped, so telling them "look for the one with the light out" may also help.)

I am handy enough to do the GFCI replacements

Do you know the difference between the "line" and "load" terminals on a GFCI?

I am assuming that each room gets a run from the breaker box that splits to switch/light and receptacles that are in series, right?

That's one way to do it. On normal-ish sized rental houses (less than maybe 2,000 square feet), it's fairly common for the receptacles and lights in a couple of rooms to all be on the same circuit. There is also a suggestion, not always followed, that in any given room, the receptacles should be on one circuit and the lights on another - that way, if somebody plugs something in and pops a breaker, they aren't also plunged into darkness.

Bathrooms are special and different. Kitchens are special and different. The laundry is special and different. If your locality requires AFCIs, the bedrooms will be special and different.  Reading the book (see below) will tell you how, and what to do.

I should be able to talk with guy at the big box store for cable size and the like.

Some big-box employees will help and some won't.

I would strongly suggest that you go buy a book (don't Google) on how to do wiring in a house. The big-box store sells one with lots of pictures for $20 or less; you probably already understand the "how to wire up a receptacle" chapter, but pay lots of attention to the "how to wire the whole house" chapter. They probably also sell a small paperback called "Wiring Simplified", by Hartwell, Richter, and Schwan. It has a green cover with a picture of wires on it and costs about $10. It's a little light on illustrations, but it tells you how to wire up an entire house, correctly. Even if you end up hiring an electrician, that $10 will allow you to have more intelligent discussions with them.  (I have a few different versions of this book... including the 1954 edition that my dad bought back in the day to help him install a 240 volt room air conditioner at home.)

Also, since they had an attic fan at one time, I would assume none of the exterior walls are insulated.

Not necessarily. The house I grew up was built in the mid-1960s with insulated exterior walls, blown-in insulation in the attic, and insulation under the floor (it has a full basement), and Dad put in an attic fan in the early 1980s. My current residence is a few years newer, but has a similar situation. In the Midwest, the attic fan basically gives you 2 to 4 weeks in the spring and 2 to 4 weeks in the fall where you can run the attic fan alone, before you give up and turn on the A/C or furnace respectively. Not sure how it goes on the Gulf... if you're used to the humidity, just having moving air might be enough to help you feel cooler.

(From your later post)
I didn't realize that grounding to the box is acceptable.

Grounding the receptacle to the box is acceptable IF THE BOX IS GROUNDED. If the house was wired with two-wire Romex (nonmetallic cable), the boxes will NOT be grounded. For 1968, you might find that the kitchen and bathroom boxes *are* grounded, but nothing else in the house is.  (For a while, the metal boxes were grounded by using cable with a ground wire, and attaching the ground wire to the outside of the box, so it might be grounded even if you can't see a ground wire inside the box.  The (probably original) kitchen outlets in my mid-1950s rental were done this way.)

You can tell for sure with the 3-light tester and the 3 prong - 2 prong adapter I talked about before. Take out the screw in the cover plate, plug in the adapter, and then put the screw back in through the tab in the adapter. (This connects the adapter tab to the metal mounting strap of the outlet, which is hopefully in good contact with the outlet box.) If both of the "good" lights on the tester come on, then the box is grounded.

Another way to tell is with the tester that has a small neon bulb in a plastic "cage", with two short test prods sticking out of the bottom. First, find an outlet at home that you trust and plug one prod into the narrow slot and the other prod into the wide slot. See how bright the neon is? Remember that.

At the rent house, take off the cover plate and touch one prod solidly to the metal box. Then try the other prod in each slot on the outlet. If one of the slots makes the neon light up nice and bright, then the box is grounded. If the neon glows dimly or not at all on both slots, then the box is not grounded.

Don't use a voltmeter for this test. (Once you understand why not, you don't need my advice anymore. :D )

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