I have a condo and I want to run some Coax and twisted pair from the attic to the ground floor for service to a TV/Entertainment center.

Problem: The wall that I intend to run the wires down is 19' from ceiling to floor continuous, and on the other side of the wall is the floor of one of the bedrooms. I am pretty sure that since the wall is interior that the wall is hollow, but when I get to the floor joists of the bedroom, what can I expect to find ? The bedroom is standard 8' wood stud'ed walls probably with 2x4" across the top and bottom. My guess is that the floor joists are probably 2x10" with and end-cap that is either 1 or 2 2x10" w/1/2" plywood between for spacing.

Whats the best way to get the wires through this floor to the next wall section below ?


*Cut a hole in the ceiling above your final destination (Using my 45 degree technique). The hole in the ceiling should give you a peek as to any obstacles in the way. Condo floors and ceilings tend to be loaded with utilities and it is easy to drill into something. You may find that the floor joists are actually trusses instead of solid wood. They are used to faciltate the installation of ducts and pipes. The trusses also make it easy to fish wires across the ceiling. If you have clearance in the ceiling below, cut a hole in the wall at the floor above a few inches above the baseboard molding big enough to get a drill and drill bit it in. You will need to drill twice. One hole through the top of the truss and wall plate and one through the bottom of the truss or support plate. Sometimes with my angle drill and a short auger bit I am able to drill down from the hole in the ceiling into the wall below, thus having one less hole to patch. If this is a bearing wall it may be solid wood where you want to drill down to. Condos are tricky because there is structure in place for the entire building. It is best to do some exploratory surguey first to see what you are up against.

One thing that you may find is that 19' wall may have additional blocking in it for firestops and to keep the studs from bending. If so you will need to notch around them.

I usually measure the thickness of the floor at the stairs to determine if trusses are used. If the floor thickness is 12" or less it could be solid. If it is thicker, like around 15" then you have trusses.

My 45 degree technique is simply cutting the hole in the drywall at a 45 degree angle. This way the drywall can be buttered with joint compound and the piece can be put back in where it came from without any taping. I butter both the wall and the piece to bring it out to nearly even with the original wall. Let the joint compound dry overnight and skim coat it the next day.

John Grabowski
http://www.MrElectrician.TV