How to make connection at existing switch?

My bathroom has two doors. There is a light switch outside one door. I would like to put a 3way switch outside the other door.
Putting in the new switch is easy enough, as is running the cable through the attic and down to the old box, but how do I get the cable into the the first steel box? Since I do not have access to the outside of the existing box, I cannot put a cable clamp on it. Do I just live without a cable clamp? Obviously I can not secure the cable to the wall, as required by code either. It seems to me that any work like this will be against code unless you rip the drywall off. Any help would be appreciated.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Wade Lippman wrote:

Look for a product called a 'hitlock'. This will solve your box problem, if you can find them -- it's been a while since I've seen them retail.
(You're talking about Romex, correct?)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
http://www.cornerhardware.com/item_268204/Electrical/Wire_Cable/Cable_Box_Connectors/Dual_Hitlock_Romex_Connector.html
"Robert A. Barr" wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Do you really have a clear shot? Are there any firebreaks and/or diagonal braces?
but how do I get the cable into the the

existing
Most metal boxes that I have used have clamps that can be added through the inside of the box. You may have to salvage an old box or buy a new box in order to get the clamps.There are also plastic snap in cable clamps that may work here. That is if the box has a standard 1/2" KO where you need it.
Obviously I can not secure the cable to the wall, as required by

Staples are not required for retro work in finished walls (NEC 336-18 exception 1). Most of the reasons for staples are to keep the cables from being caught sheetrock panels and studs during original construction etc. Staple it where you can in accessible locations such as the attic.
Any help would be appreciated.

Most of the time when I am in your situation I end up prying out the old box. If I destroy the box or can't get it out of the wall without damaging the sheetrock to much, then I just let it fall into the wall cavity. Then I drill up/down through firebrakes if needed and fish the new wire. Then I install a new box. Kevin

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 20 Aug 2003 12:37:23 GMT, "Wade Lippman"

There's different code for old work.
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
'nuther Bob wrote:

Not completely legal but I've seen one case where a cable clamp was put in from inside the box (inside out but it clamped the cable OK!). Or change the box to one with built-in cable clamps. Or niggle away the plaster sufficiently on one edge of the box to put a cable clamp from outside and then use a much bigger 'decorative style' switch plate to cover up the broken plaster edge adjacent to the box? I've seen switch plates twice 'normal size'. As someone mentions there are plastic cable clamps which, sort of, 'snap' into place. Also there are plastic boxes that have the sort of clamp that mainly 'rests' on the incomiing cable and prevents it from pulling out of the box, thus avoiding any strain on the actual wiring connections. Browse around an electrical supplies place for ideas.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.