My house is about 70 years old. The main floor is not grounded. How difficult a job would it be to upgrade the wiring so that it is grounded? Thanks.

 

There are many things to take into consideration for a job such as this. Many varibles come into play. Access to the wireing makes the job much easier. Being it is the first floor is there a basement under the floor? What is in the walls? How much damage to the walls are you willing to repair? The job itself is not difficult in theroy but if your fighting hardwood in the walls and no easy access then it becomes hard to do.
I would suggest reading some books on the subject and then taking a long look at what you have to do, this way you can get a much better understanding of what is needed.

 

What do you have for power tools? If you have lath& plaster walls you'll need a "jig" saw for cutting the laths and a power screw-driver for drywall screws for mounting outlet-boxes.----Good Luck!!!

 

There is a crawl space under the floor which is high enough to comfortably be on hands and knees. The walls are lathe and plaster, except for a few spots that have been repaired with drywall. I've got a good supply of tools and experience with non-electrical projects (and minor electrical). Just wondering if this is something that can be done DIY or would the cost of hiring an electrician be worthwhile.

 

This is to your advantage. You can come up into the wall cavity from below. You should not have to cut the wall open except where you want to instll new boxes. From above pound a small diameter nail intothe floor right at the base bords and go under neath and find now you can dirl up intothe wall cavity be drilling a hole abot 2 inches over from the nail. If the wire already go dowm then you have a guide. You probably won't be able to pull the old wire out but you can drill beside it.

Another option that sometime works is removing the baseboards. You can run the wire though the walls at the bottom behind the base boards. There is usually no plaster behind base boards on plater lathe walls.

 

I'll give you a simply assignment to start off with------installing one receptacle outlet box.

First, fix the height of the box, say 16" from floor to center-of-the-box. Next, locate a stud that will be on the Left side on the outlet-box.Use a Deep plastic gem-box for the receptacle outlet-box and scribe the out-line of the box on the wall with the Left side of the box aligned with the side of the stud.

Remove the plaster with a hammer and chisel and then cut the lath away with a jiq-saw..The first cuts thru the lath is on the Right side of the opening and the second cuts on the stud-side of the opening.

The box should fit neatly into the opening with the Left side of the box firmly against the side of the stud. Drill holes is the stud- side of the box for screws that will fasten the box to the stud. When the box is fastened, the front edge of the box will be "flush" with the face of the plaster.

Before you fasten the box to the stud be sure you have openings in the box for the cables to enter the box.I advise using #10 sheet-metal screws and 1'4" fender-washers for fastening the box to the stud.

Want to "give it a try"?-----Good Luck!!!

 

Is that an approved method for mounting the box?

 

I have welded them on places. I wonder if thats another approved method?

 

Your best and easiest "fix" is to simply install a GFI receptacle at the first outlet location on each circuit and then change all your ungrounded receptacles to 3-prong grounded types. The wiring to the downstream receptacles is attached to the "load-side" screws on the GFI so they will all be protected. You will still not have a "ground" in your circuit, but most things you plug into a house receptacle don't need a ground because they have two-prong cords. This method of protection is code compliant and I have done it many times when homeowners are simply interested in changing out their old 2-prong receptacles to new 3-prong ones.

You may have a couple of locations where you desire a truly grounded receptacle such as in the kitchen or at a computer desk. Run dedicated circuits to those areas and install new outlets. Your location may be right next to an existing ungrounded outlet. If possible, you can remove the wiring from the existing box (cut short and pushed out) and fish a new cable into the box so you won't have to cut in a new box.

Unless you are adamant about replacing all your wiring, it would be much easier to identify the crucial locations where truly grounded and dedicated circuitry is needed and concentrate on those few areas. Simply protect the remaining wiring with ground fault protection.

 

What mcjunk said!!!

Also as an aside, install the blue "remodel" boxes if you want a new rec. box. You cut the hole to size in your drywall insert box and two flanges "pop" up as you tighten the screws. Be careful not to cut into studs but it gives you more flexibility on box location!!
Tim