Uh oh... gotta cut in-wall metal conduit for new outlet!

miamicanes

Active Member
Well, I just finished cutting a hole in the drywall where my first new outlet is going to go, and made a discovery... I'm not yet sure whether it's cause for celebration (I don't need to run a new set of power lines after all) or agony (thick metal pipe, small hole, general home-improvement tools... ouch).

The conduit looks exactly like the gray electrical conduit they sell at Home Depot, but it's metal... probably steel. Quite solid. The wires inside it are loose, so if cutting the conduit leaves me with two sets of wires that are too short, I can easily string new ones from adjacent outlets along the same conduit.

That said, what's the best way to go about cutting it that won't involve the purchase of more than $50 worth of new tools at Home Depot? Right now, I have a ~4x4 hole cut in the drywall, with the conduit passing from left to right in the center. Ultimately, it looks like I'm going to have to cut the conduit in two places, somehow wrestle a new box into position, and attach the conduit to that new box. Is THAT even likely to be POSSIBLE, or am I probably going to have to cut the conduit in two places to create a gap big enough for the new box to fit between them, then pull out ALL the wire leading to adjacent receptacles, and pray that there's enough room inside the original conduit to let me shove Romex through it (so the fact that the original conduit won't be mechanically-fastened to the new box won't be a code violation since the wire running inside of it is technically approved for direct runs inside walls anyway)?

Any saw suggestions? Since I'm probably going to have to enlarge the hole in the drywall, am I better off making two tall, narrow vertical extensions to make room for the hacksaw blade, on the theory that the narrow holes will be easier to patch? Or would it ultimately be easier to just find the nearest stud, and cut away a 2x2 foot square around the whole area and just plan to replace the whole section with a new piece of cut, taped, and pasted drywall?

This is all virgin territory to me right now... I've never cut a hole in drywall that was too big to fix with a 6"x6" metal patch, nor have I ever cut metal pipe... in OR out of wall.

Obviously, it goes without saying that I'm going to have ALL the house power turned off while the cuts themselves are taking place, just in case someone left a "hot neutral" in there at some point over the past 25 years :)
 
Here are some pics to clarify what I'm talking about. One thing that might not be obvious from the pics... the insulation is about 1/2" deep, and there's solid concrete behind it. So any back-and-forth sawing is going to have to take place in the vertical plane.


The first is an overview of the hole with the conduit running horizontally through it.

wall1.jpg

The second pic is a closeup of the hole.

wall2.jpg

The third shows a nearby box originally built for an outdoor antenna that I'm repurposing into a double-gang 12-bay keystone media port. I included it because it shows more of the surrounding inside wall detail.

wall3.jpg
 
As far as the pipe cutting goes, it sounds like doing it with a hacksaw will really kill your neck, back, shoulders, etc.
If you already have a Dremel or similar tool, I would suggest just using cutoff wheels to cut the pipe. The fact that there are no sharp edges on these also makes it harder to accidentally cut the wires inside.
 
1. Is that mold in the last picture? If it is you may want to seriously consider just ripping out the drywall and replacing it. (I know that wan't a question)
2. I would maybe take a shot at that conduit with a dremel and cutting wheel - but I'm certainly no expert.
 
I would leave it be and mount the box next to it and run a new wire myself but thats just non-electrician me.
 
> Is that mold in the last picture?

You know, that's a really good question. I kind of freaked out myself last night when I first saw it. It kind of looks like at some point in the past, water seeped in along the conduit leading to the rooftop antenna. There were some bright yellow stains, covered by about 3 layers of old paint, a layer of textured wallpaper, and at least 2 or 3 more layers of paint. I've seen absolutely no evidence of recent water damage (and we've had plenty of torrential rain all summer), so I think whatever caused the water problem was fixed in the distant past.

Insofar as the mold goes... well... I don't really KNOW what to do about it. More precisely, I have no idea about its scope, or whether ripping out and replacing that entire wall would actually make any real difference in the grand scheme of things. If I knew with reasonable certainty that there was mold in just that one place, or one or two other specific places, I'd rip out the drywall in a heartbeat. But I absolutely can't afford to just wantonly rip the house down to the furring strips and studs & replace ALL of it. Is there any good way to detect the presence of mold in specific sections of drywall? I know they can test a HOUSE to see whether it has a "mold problem", but can they actually discern anything SPECIFIC about WHERE mold might be, and how bad it might be in those specific areas?

This IS a bit of a breakthrough for me, because my kitty has had respiratory problems ever since we moved in. So far, I've spent close to $2,000 having him screened for lung cancer, heart disease, and asthma, and had him on 3 courses of antibiotics for secondary infections he picked up along the way. The best I've gotten from his doctors so far is, "He's probably allergic to SOMETHING, but it's almost impossible to tell you WHAT he's allergic TO."

Groan. I think the scope of my home improvement project might have just exploded on me. But anyway, getting back to the mold... IS there any way to get answers like, "there's probably no mold in this area, there's probably some mold in this area, and if you rip out THIS section of drywall, wear a respirator because THAT's the "mother ship"... ?
 
There are mold test kits you can get over the internet, but I don't know how well they work.

You DO have to especially watch out for the Stachybotrys mold type. I know there are companies out here in Las Vegas that do mold remediation by testing and then applying chemicals to neutralize specific mold types. Do you have any such companies in your area? Perhaps give them a call.
 
I have no idea what the electrical code is for conduit entombed in foam. My rule of thumb is to duplicate whatever I find ... so if all outlets are installed in boxes attached to the conduit, then it is safe to assume you need to duplicate this convention. I have my doubts about this assumption:
... shove Romex through it (so the fact that the original conduit won't be mechanically-fastened to the new box won't be a code violation since the wire running inside of it is technically approved for direct runs inside walls anyway)
I suspect that if all boxes were originally installed the way you suggest (not mechanically attached to the conduit), the building inspector wouldn't have approved it.

My neighbour's basement had flooded and the insurance company required that he have the basement inspected for mold. A certified "mold sniffing dog" was used to detect mold. The critter walked around and pawed any wall allegedly containing mold. The handler marked the spot with a big "X". Took about an hour and cost $500 dollars. The lower part of all basement walls, 125 linear feet and one foot high, was removed and replaced. I saw only one area that had visible mold and a detectable odour ... but who am I to argue with a dog that makes a half-grand an hour.

It's hard to tell from the photos (could be old paint, dirt, or other cruft) but it really does look like your wall has become a petri dish. According to Maslow's Hierarchy of Home Improvement, mold removal trumps new outlets.
 
As far as the mold goes, I was faced with a possible mold issue when I bought my current house. The best advice I got was to look for someone to do the testing that does not do remediation. This helps prevent the chance of what I will call a "crooked auto mechanic" diagnosis.
If the air is really a problem, you may want to seek an Indoor Air Quality (IAQ) specialist rather than just a mold person. There are many things other than mold that can cause allergies and other IAQ problems.
 
We have a semi-permanent china cabinet in our dining room that we detached from the wall to repaint. Behind one there was a small amount of mold. We were concerned so we had a specialist come out. They determined the mold was from an air conditioning duct that was blowing air behind the cabinet and condensing. Luckily there was no other mold and they didn't even rip out the drywall that had the mold on it. They simply treated it in place and modified the air duct to prvent future problems.

So the moral of the story is that mold isn't necessarily a "remodeling kiss of death" :) It just depends on the situation, the type of mold and size of the area effected. I would certainly have an expert come in and inspect the problem and figure out a course of action.

Unfortunately, mold is one of those things that if you ignore it hoping it will go away - the problem just gets worse. Once you think there is an issue, it is better to take care of it right away.
 
Well, I definitely have a problem, though I'm still trying to determine its scope. I've attached a few photos. I cut out the entire section of drywall below the old cable outlet, as well as a small section above it. The section above looked fine. The section below was, um... shall we say, "lively"? I don't know how I managed to not see it or make sense of it, but if you look at the pics, you can see that the ENTIRE WALL's lower foot is discolored (and, I'm guessing, is probably hosting more mold).

wall4.jpg

Interestingly, the upper extent of the discoloration seems to coincide with the lower side of the furring strip. I suspect that suggests that the furring strip CONTAINED the dampness, rather than acted as the conduit that brought moisture to the area in the first place. My first hunch was that water was entering through the ancient, long-disused conduit leading to what presumably used to be a roof antenna when the house was first built... but after noticing that the discolored area is 14 feet wide, and wraps around ~2 feet into an adjacent corner, I've kind of discounted that theory because the damage seems to be too wide and too consistent.

wall5.jpg

I'm 99.8% sure it's not due to standing floodwater from some past flood. Before the tropical storm a few days ago, I talked to a neighbor who's lived there since the complex was built, and he swore that the area has never, ever been flooded. He had no reason to lie about it, so I think I can safely assume that flooding isn't the reason for the damage & mold.

Any ideas what to do next? I barricaded off that half of the living room with a plastic tarp and masking tape (mostly to keep my cats out of the area), and I'm tentatively planning to cut away all the drywall below the furring strip (or at least keep cutting until I see consistently clean mold-free drywall). The sliding glass door opens up into the "closed off" side of the room and leads directly to the garbage can, so at least I won't have to track it through the house. Will I have an easier time repairing it if I try to cut away EXACTLY the lower 2 feet of drywall (vs 12-15"), so then I can just cut new sheets in half and screw them in place? Or would a better strategy be to cut away ~18-21", to ensure that I won't end up with a horizontal section that's just *slightly* too tall for a 2' section?

Will spraying lots of Lysol onto the foam, and in the surrounding area throughout the entire process, contribute any meaningful benefit? Or will it just put lots of aerosol disinfectant into my lungs, increase my odds of slipping on a wet spot, and/or metaphorically "piss off the mold" rather than kill it?
 
You mentioned tropical storm and your handle is "miamicanes" so I guess you live somewhere in Florida. I live in Montreal so that hardly makes me an expert on home construction in your area. If I were to take a guess, I'd say your home is built on a concrete slab and the 2x4 (baseplate of the wall seen in the photos) is resting on it.

The baseplate is either wicking moisture that is drawn by the concrete (concrete is not waterproof) or from water infiltrating the wall's exterior. The drywall's paper wicks the moisture from the baseplate and forms a warm, dark, humid area suitable for growing mold. The furring strip acts as an absorbent sponge and effectively seals in the humidity and prevents further wicking ... so you see little evidence of mold above it.

If too much rain water is collecting along the outside wall (runoff from the roof or lawn) it can leach through the concrete or simply find its way through seams or breaches in the exterior (siding? stucco? brick?). Make sure your home has proper drainage.

Removing 2' of drywall makes sense .. but you'll need to add a furring strip under the seam for strength. The seam will have one butt edge (the existing drywall) and one tapered or butt-edge (the new drywall; your choice). You'll want a professional plasterer to finish this kind of tricky seam. Or you can be a sneaky bastard and cut the drywall at chair-rail height. Put the butt-edge of the new drywall up against the existing drywall's butt-edge and cover the seam with chair-rail molding (mold-ing ... how ironic). Let the next homeowner discover what ugly secrets lie beneath moldings.

Removing the existing mold depends on how and what is affected. The drywall is toast. If the baseplate looks like aged cheese, it has to go too (and may require specialized carpentry skills). If it is only on the surface, then it can be washed/scraped/sanded away. After everything is clean and dry, you can apply a mold-inhibitor that is approved for indoor use. If you plan to do any of this yourself, I recommend you buy a good silicone dustmask with approved filters (rated for mold; not just a 'coffee filter').
 
As far as I can tell, the foundation is a concrete slab. There's definitely a vapor barrier (built after 1980). The wall you see depicted was built with concrete blocks that were reinforced and grouted in SOME holes, if not ALL holes. 3/4" furring strips were attached every 24", with an additional one at baseboard height, and (apparently) at least one more that's just below the wall outlets, drywall was screwed on, and expanding foam insulation was applied at some point before or after the drywall.

What's making things hard is the fact that I haven't found any obvious wet spots, or even moist ones. Tonight I'm going to tear into the wall in the adjacent room to the right to see how far the damage extends. Further to the right of the outlet pictured (towards the rear of the house), things get more complicated, because THEN I have the kitchen and laundry room, and THEIR wall IS, in fact, a "real" 2x4 (steel stud) framed wall that's set about 6" further back from the "real" concrete wall to make room for the pipes and stuff. Of course, it's occurred to me that the kitchen or laundry room might be the source of the problem to begin with. I'll probably have a better idea after another hour or two of wall exploration...
 
OK, I get it now. Not a 2x4 baseplate but a furring strip. I still believe the lower strip is wicking moisture either from the slab or from a breach in the exterior wall (cinder blocks).

I don't know if you just moved in recently but you might want to have a little chat with the home inspector you used to scope out this place before you bought it. They don't catch everything, especially if it is in a sealed wall, but this looks like a serious "miss".
 
OK, I get it now. Not a 2x4 baseplate but a furring strip. I still believe the lower strip is wicking moisture either from the slab or from a breach in the exterior wall (cinder blocks).

I don't know if you just moved in recently but you might want to have a little chat with the home inspector you used to scope out this place before you bought it. They don't catch everything, especially if it is in a sealed wall, but this looks like a serious "miss".

If you want to cut it - easy to do with an angle grinder.... but if it is carrying high voltage wire....don't cut it.

As far as I recall, NEC code specifies that any wire join has to be accessible and in an approved box. there might be more details relating to code - for example should the face plate on the box has accessible (meaning you'd have to put a blank plate on it that can be opened. Wire should be stapled within sevral inchines of the box

if this werent done, for example If somoene pulled the wire from the other end and the joint came apart, sparking inside the wall could cause a fire.

make sure you know the code if you are going to cut it.
 
Back
Top