New wiring in an old (1948) home

patnancy · 11-30-2010, 04:22 PM

I'm wondering how the rewiring of an older home is accomplished. Do the walls have to be ripped open or is there a non-destructive way the old wires are removed and the new installed? If we're going to have to have our walls torn apart I'm not so sure we'll want to do that.

Thanks!

rjniles · 11-30-2010, 04:56 PM

It depends on the construction and layout of the building. Often most of the wiring can be fished into the walls with little destruction. But a few holes and wall or ceiling repairs are almost inevitable.

HandyFrank · 11-30-2010, 04:57 PM

Does the house have an accessible attic or basement? If so, that makes the job a lot easier.

As rjniles said, expect a few holes that will need to be patches naturally when dealing with plaster/sheetrock.

VersaBar · 11-30-2010, 05:01 PM

The layout of the house is key. If you have an open attic above the entire house, there is a good chance you can rewire the entire house without more than a few holes. A basement or crawlspace underneath will make it pretty easy too, altho it's a bit more work getting new switchlegs up to the lights without attic space.

Sometimes you hit fireblocks in the walls, but I have always drilled thru them with long drill bits. Even if some holes have to be made, it's relatively easy to patch them.

As for the old wiring, it can all stay. Make sure both ends are disconnected, cut it as short as possible, and bury it so no one can hook it back up in the future.

Rewiring an old house yourself is one of the biggest DIY ways to save money.

patnancy · 12-01-2010, 01:45 PM

The good news is we have an attic (fairly open) and we have a 'mostly' finished basement. So, the wiring is somewhat easy to get to but one thing I wondered is about whether the new wiring needs to be stapled to the 2x4's or anything like that. ? It's okay to just run it willy nilly through the walls?

Thanks for the responses.

VersaBar · 12-01-2010, 01:54 PM

Yes, if you are not opening up the walls you can just snake the wires loose inside the wall cavities. It's perfectly safe, the boxes you use will clamp onto the wire and you can staple the wire where it comes up into the attic.

First thing you need to do is make a plan, you'll need to adhere to all the current codes as far as wiring, this might require you to install a lot of new receptacles where you never had them and a lot of separate circuits.

Since you are living in the house, it's best to tackle this job by only doing 1 or 2 circuits at a time, this way you limit the places that are out of power. One of the biggest issues can be removing the old boxes, this can range from very easy to extremely nerve racking. You need to clean the plaster away from the front of the box enough to pry the box away from the stud enough to get a sawzall blade in there to cut the nails. Sometimes it goes easy, sometimes huge chunks off plaster fall off the wall

Once the old boxes are removed, it's just a matter of abandoning the old wiring, pulling in the new, and then installing old work boxes in the openings. This is a perfect instance to use "Smartboxes" or the "Onebox" which get screwed directly into the stud instead of relying on the wall covering (plaster) to hold it up. Since you know all the openings are already next to studs, this type of box will fit right in and mount quick.

jerseyguy1996 · 12-12-2010, 06:37 PM

Not sure if the OP is still checking this thread but I am in the process of rewiring my old house. This was my experience. Pulling out the old outlet and switch boxes was one of the hardest parts because they were plastered into the wall. This meant cutting out large holes to get the boxes out which meant the whole was two big for the new box. I found the best thing for me was to patch the hole over completely as if there was never a box there and then cut a brand new opening for the new box. I patched by gluing and screwing 1x's to the back of the finish surface in the wall to give myself something to screw some layers of sheetrock to. The plaster wall was thick so it took two layers of sheetrock to fill the depth. Then I used setting type joint compound to smooth over the sheetrock and I feathered that into the rest of the wall. A few quick passes with the random orbit sander finished the job. Then I cut new openings that were exactly the size of the new boxes. I used this kind of box:
http://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

After installation and paint over the patch you can't even tell that anything was done.

jimmyfloyd · 12-12-2010, 11:40 PM

Good information here.

RST · 12-13-2010, 12:13 AM

Are you required to replace the boxes? My existing boxes (circa 1949) seem fine, though a little small.

The hardest part for me has been getting new wires into old boxes, for example when extending a run of receptacles.

Robert

rjniles · 12-13-2010, 06:20 AM

You are not required to replace the box as long as it has enough cubic inch capacity for the number of conductors you are using. However it is much easier to get the wiring fished into the wall when the box has been removed.

Jim Port · 12-13-2010, 08:00 AM

The clamps in the back of the old box may be the wrong type for the wiring method you are installing. They can be changed, but I have never seen the clamps for sale without a box.

RST · 12-13-2010, 12:08 PM

Quote:

Originally Posted by Jim Port

The clamps in the back of the old box may be the wrong type for the wiring method you are installing. They can be changed, but I have never seen the clamps for sale without a box.

Ahh, I could see how that would be a problem if changing wire types. I am simply replacing older NM wiring (14-2 or 12-2, black, cloth?) with new NM wiring (12-2), so it sounds like I am OK to reuse the boxes. None of the old boxes have more than 2 cables anymore; if I need more than 2 cables in a box I use a new box.

RST

Jim Port · 12-13-2010, 12:19 PM

In the older editions of the electrical code you only needed a deduction of 1 conductor for each device like a switch or receptacle. Now you deduct two for each device. You boxes may be too small.

Can you see how deep the metal boxes are or a cubic inch capacity stamped on the inside back of the box?

Each #14 will be 2 cubic inches. A #12 will be 2.25 cubic inches. Internal clamps count as one conductor. A ground counts as one regardless of how many. For example 2 14-2 cables in the box; 4 conductors (blk and wht)+ 2 device + one clamp + one ground = 8 *2 = 16 cubic inch minimum.

HandyFrank · 12-13-2010, 12:25 PM

If the new boxes are the same size as the old box it might be easier to just get new boxes. However, in my house the old boxes were very small and some were in the baseboard, so to not have to do a lot of modifying and cutting I re-used the old metal boxes in certain places. Just take your time to make sure they sit flush, and that you have the correct amount of wires within.

RST · 12-13-2010, 01:55 PM

Sounds like I'd better do some measuring. They seem large enough, but I'm not sure they are a full 18 cu in (8 conductors x 2.25).

I'm not sure if would be more of a pain to patch the walls or install junction boxes in the crawlspace, neither sounds very attractive.

RST

11-30-2010, 04:56 PM	#2
rjniles A "Handy Husband" Join Date: Feb 2007 Location: South Carolina Low Country Posts: 2,961	New wiring in an old (1948) home It depends on the construction and layout of the building. Often most of the wiring can be fished into the walls with little destruction. But a few holes and wall or ceiling repairs are almost inevitable. __________________ Location: Coastal South Carolina

11-30-2010, 04:57 PM	#3
HandyFrank Member Join Date: Jan 2010 Location: CT Posts: 137	New wiring in an old (1948) home Does the house have an accessible attic or basement? If so, that makes the job a lot easier. As rjniles said, expect a few holes that will need to be patches naturally when dealing with plaster/sheetrock.

11-30-2010, 05:01 PM	#4
VersaBar Electrician Join Date: Nov 2010 Location: NJ Posts: 87	New wiring in an old (1948) home The layout of the house is key. If you have an open attic above the entire house, there is a good chance you can rewire the entire house without more than a few holes. A basement or crawlspace underneath will make it pretty easy too, altho it's a bit more work getting new switchlegs up to the lights without attic space. Sometimes you hit fireblocks in the walls, but I have always drilled thru them with long drill bits. Even if some holes have to be made, it's relatively easy to patch them. As for the old wiring, it can all stay. Make sure both ends are disconnected, cut it as short as possible, and bury it so no one can hook it back up in the future. Rewiring an old house yourself is one of the biggest DIY ways to save money. Last edited by VersaBar; 11-30-2010 at 05:03 PM.

12-01-2010, 01:45 PM	#5
patnancy Newbie Join Date: Oct 2010 Posts: 11	New wiring in an old (1948) home The good news is we have an attic (fairly open) and we have a 'mostly' finished basement. So, the wiring is somewhat easy to get to but one thing I wondered is about whether the new wiring needs to be stapled to the 2x4's or anything like that. ? It's okay to just run it willy nilly through the walls? Thanks for the responses.

12-01-2010, 01:54 PM	#6
VersaBar Electrician Join Date: Nov 2010 Location: NJ Posts: 87	New wiring in an old (1948) home Yes, if you are not opening up the walls you can just snake the wires loose inside the wall cavities. It's perfectly safe, the boxes you use will clamp onto the wire and you can staple the wire where it comes up into the attic. First thing you need to do is make a plan, you'll need to adhere to all the current codes as far as wiring, this might require you to install a lot of new receptacles where you never had them and a lot of separate circuits. Since you are living in the house, it's best to tackle this job by only doing 1 or 2 circuits at a time, this way you limit the places that are out of power. One of the biggest issues can be removing the old boxes, this can range from very easy to extremely nerve racking. You need to clean the plaster away from the front of the box enough to pry the box away from the stud enough to get a sawzall blade in there to cut the nails. Sometimes it goes easy, sometimes huge chunks off plaster fall off the wall Once the old boxes are removed, it's just a matter of abandoning the old wiring, pulling in the new, and then installing old work boxes in the openings. This is a perfect instance to use "Smartboxes" or the "Onebox" which get screwed directly into the stud instead of relying on the wall covering (plaster) to hold it up. Since you know all the openings are already next to studs, this type of box will fit right in and mount quick.

New wiring in an old (1948) home