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Intro / Question about old work boxes

1205 Views 5 Replies 5 Participants Last post by  earlieq

First post from a new member. I've done the usual amount of DIY stuff over the years in a few different homes, including minor electrical work. Last year my wife and I bought an old house, 1870s-era we believe. There is lots to do, and the biggest focus for me now is electrical. I'm not an electrician, just an interested and careful amateur. I've bought some books, done a lot of reading online, and in general I look for resources that help me understand the issues.

I've discovered that most of the original wiring was on one 15A circuit, which was all knob-and-tube. Additional circuits have been added since then, and the K&T has been extended in places via romex and electrical tape (and probably prayer). My long-term goal is to replace all the K&T, one circuit at a time, by putting in an entirely new circuit. Likewise, some of the newer (post-K&T) circuits are two-wire with no ground, and I want to replace all those as well. Being an old house, there are of course not enough receptacles in the right locations, so i will be adding more of those as well.

I'm sure I'll be writing with questions but the first question is, does someone make an old-work box intended for old plaster walls? I've replaced a few boxes so far (light switches etc), and it's been a battle each time. The typical Home Depot old-work box does not always accommodate the thickness of plaster+lath.

I've been reading diychatroom for a few weeks, and I'm very impressed with the quality of the advice and answers I've seen here. Thanks everyone,

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...I've bought some books, done a lot of reading online, and in general I look for resources that help me understand the issues...
Good for you for reading about this first! People used to do that, but not so much these days...

Anyway go to, click on "Images" on the top or left, then search for the following words...

old work electrical box

You will see there are many different types of old work boxes available. Some of the plastic kind have a tab at the end of a screw. You could always get a longer screw if necessary.

Anyway check at hardware stores and electrical supplies (where electricians shop) as well.

Then the following is how to install an old work box in drywall. For plaster and lath, just add a lot of curse words to the following :)
Best old work box for plaster/lath are the Slater boxes from Pass & Seymour.
There are endless methods to use for cutting in old work. You will probably discover what works best for you with time and lots of practice. A lot depends on the type of plaster walls that you have. I usually prefer metal old work boxes with madison straps. If you have plaster and lath you have to be careful that you don't loosen too much plaster from the lath or there is nothing left for the box to grip on. My house has plaster over a plaster board with a layer of rock lath board so the walls are pretty thick and don't work too well with the plastic old work clamp boxes. If you are using the plastic boxes then the ones that the last poster had the link to are better than the blue big box store type.
If you are using power tools to cut the plaster you have to be careful not to use a tool that vibrates too much because they can cause the plaster to release from the lath.
I still prefer to cut out boxes with a keyhole type saw. I usually score the outline of the cut out with a utility knife and start the point of the saw into the plaster. If there is wood lath behind it I leave that intact and cut that out separate with a wood blade.
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Have you had the incoming power line up graded and a new panel installed yet?
If not do that first.
That way you have a safe, legal place to run the new wires to.
To cut the holes I use a Roto Zip with a tile cutting blade, goes though plaster or plaster board like butter.
Thanks for the input, everyone.
Joecaption, yes I had the Federal-Pacific service panel replaced by a real electrician. Current service is 200A with a Siemens G4040B-1200 panel.
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