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Nonmetallic Sheathed Cable

Throughout the vast majority of the U.S.A., nonmetallic sheathed cable (NM cable) has been the most common type of residential wiring system since about the early 1950’s.  And it’s had a pretty good track record of success.  It consists or two or more insulated wires along with a bare ground wire, wrapped in paper and then contained inside a thermoplastic outer sheathing.  It’s often called Romex®, but that’s a brand name and not all NM cable is Romex®.  It comes in large spools of different wire sizes, it’s easy to install, it’s easy to cut to length, and it goes up pretty quickly.

Despite its long history of successful usage throughout most of the country, in much of the Chicagoland area this type of wiring isn’t allowed.  Chicago and many of the surrounding suburbs require that wires be pulled through some type of raceway, which usually is electrical metallic tubing (EMT) and normally called “conduit”.

So when you see NM cable in a part of Chicagoland where it’s not allowed, what should you think?  And what should you do?

The first thing to note is that if this issue is coming up when you’re buying a house then it’s likely to come up again when you sell.  So keep that in mind.

The biggest problem with NM cable in Chicagoland is that it’s often installed not by a good qualified electrician but by a handyman or homeowner.  In this case it’s not the material that’s in question but the installation methods.  When it’s exposed, NM cable needs to be run closely along the surfaces of the building finish to provide support and protection.  It needs to be supported at least every 4.5 feet and secured within 12 inches of its ends.  Where the cable enters any type of panel enclosure or junction box it needs to be clamped to the box.  These are very common defects when NM cable is installed by an amateur.

This house is in Chicago so there shouldn’t be any NM cable. Still, this is run closely along the building surfaces, it’s supported properly, and it’s clamped into this junction box for the light. It’s installed well.

This cable isn’t clamped to the box. Not done by a licensed electrician.

NM cable can only be used inside.  It can’t be used outside or exposed to sunlight.  It can’t be buried underground (there’s a special kind of cable for that) or encased in concrete or plaster.

NM cable shouldn’t be used outside. No self-respecting electrician did this.

NM can’t be used with a plug, making it into an extension cord.  It isn’t designed to be bent back and forth many times like an extension cord is.

A double whammy — NM cable run through a concrete wall and used with a plug as a glorified extension cord. Not done by a good electrician.

In an attic NM cable needs to be protected from physical damage.  Often times the cable is just run across the tops of the framing members, right where you want to step.  NM cable needs to be protected within six feet of any attic access opening, and if the attic has a permanent ladder or stairs then it needs protection throughout the attic up to a height of seven feet.

When NM cable is run in an unfinished basement along the bottoms of floor joists it needs to be attached to a running board (usually a 1×4 board fastened to the bottoms of the joists).  Or it can be installed through holes bored in the middle of each floor joist.

Cable that’s run along the bottoms of floor joists is susceptible to physical damage. First a 1×4 running board should be installed, and then the cable is attached to that.

NM cable is much more susceptible to damage from nails than is conduit.  So when NM cable is run through a wall stud hole that’s less than 1-1/4 inch from the front edge it needs to be protected with a steel strike plate to stop an errant nail from piercing the wire.

And dealing with the equipment grounding conductor (the ground wire) is quite a bit different with NM cable than with conduit, so that has to be taken into account.

So if the NM cable in your house is installed well then it’s likely to not pose a hazard, even though it wasn’t installed under a building permit like it should have been.  But if it has any of these defects described above then the risk of problems rises greatly.  And that can lead to shock, electrocution, fire, or other problems.  Electrical wiring is not the place you want to see amateur workmanship in your


I frequently get asked if my inspections include mold testing.  With this blog post I’m going to answer questions about mold and mold testing.  Much of the information here is taken from this document from the U.S. Centers for Disease Control (CDC) and it’s a great place to go for more detailed information.

Another great resource is the U.S. Environmental Protection Agency and their website:

The first thing to understand is that there is almost certainly mold in your house – in the house you live in now, in the house where you lived as a kid, and in the house you’re going to buy.  There’s also mold outside.  There’s mold pretty much everywhere in our environment.  It’s very common.  From the CDC document:  “There is always a little mold everywhere – in the air and on many surfaces.

So to answer the question: I don’t do mold testing, and the CDC (and really nobody at all) recommends routine mold testing.  From the CDC:  “CDC does not recommend or perform routine sampling for molds.

There’s really no test that can tell you definitively if there’s a mold problem in your house.  There’s mold, for sure, but is it a problem?  You can hire a specialist to take air samples, but what do those results tell you?  Nothing, really.  Again from the CDC:  “Standards for judging what is an acceptable, tolerable or normal quantity of mold have not been established.  Sampling for mold can be expensive, and standards for judging what is and what is not an acceptable quantity of mold have not been set.

So you can have air sampling done, and get back a report with some numbers on it, but there’s no authoritative answer as to whether those numbers are high or low.  So there’s really no point.

So how do you know if there’s a mold problem in your house?  Again from the CDC:  “Large mold infestations can usually be seen or smelled.”  If we can see it, it’s a problem.  Or if we can smell it, then it’s a problem.  It’s pretty much as simple as that.

Mold needs food and water to grow.  It can get food from many different sources, including paper products (like the paper facing of drywall), cardboard, ceiling tiles, and wood.  Mold can also grow in dust, paints, wallpaper, insulation, carpet, fabric, and upholstery.  Mold gets water from the environment, and that’s really where the problem is.  If there’s enough water for mold to grow then there’s too much water and you need to stop the water.  From the CDC:  “Mold growing in homes and buildings indicates that there is a problem with water or moisture.  This is the first problem to address.

Any kind of water problem is at the top of my priority list for a home inspection, be it a roof leak, a plumbing pipe leak, foundation water seepage, or a condensation problem.  Looking for water problems is the key to finding and stopping mold.  So the best mold test is really just a test for excess water, along with a very thorough inspection to look for any visual signs of mold.

But what about a mold test to determine the type of mold in your house?  Again, not necessary.  From the CDC:  “If you can see or smell mold, a health risk may be present. You do not need to know the type of mold growing in your home, and CDC does not recommend or perform routine sampling for molds. No matter what type of mold is present, you should remove it. Since the effect of mold on people can vary greatly, either because of the amount or type of mold, you cannot rely on sampling and culturing to know your health risk.

Some people refer to “black mold” as if that’s the real problem and a serious health risk.  But again that’s vastly overstating the issue.  From the CDC:  “Mold growth, which often looks like spots, can be many different colors, and can smell musty.  Color is not an indication of how dangerous a mold may be.  Any mold should be removed and the moisture source that helped it grow should be removed.

So it’s clear that the key to answering the question of mold isn’t a mold test, it’s just a very thorough inspection with an eye towards current and potential water problems.  And of course experience helps in knowing where to look.  Based on my experience, here are some important places to look.

Closets — Most closets have at least one outside wall, and that’s where water can leak in to help grow mold.  And that’s especially true if the closet is in the basement.  Plus there are usually a lot of things stored in a closet, so it’s especially important to move those stored items to try to get a look at the wall behind.  I’ve seen several basement closets that had water seepage behind the wall that was leading to mold growth, and the only way to find it was to be vigilant and move the stored items to be able to see the wall.

Mold on a below-grade closet wall.


Basements — Basements often have water problems.  Sometimes it’s seepage through the foundation or up through the floor slab.  Sometimes it’s sewer pipes backing up, or one of many other problems.  I’ve seen lots of drywall in basements that had mold around the bottom.  It’s important to look for this.

Condensation — Condensation is one source of water that can feed mold growth.  Here’s one example that I saw a while ago.

I was inspecting a rather large house and it had a separate pool house, with a family room, a small kitchenette, some small loft areas for sleeping, and a bathroom.  Being a pool house, it wasn’t heated very well.  The only heat source was in the family room, and there was no heat source in the bathroom – strike one for the bathroom being cold.  Plus the bathroom was in the corner of the building, and that’s often the coldest area because a corner room has more exterior wall than other rooms – strike two for the bathroom being cold.  Now look down at the baseboard around the floor, and that’s usually the coldest part of a room because warm air rises – strike three.  Now look in the corner, which is usually the coldest part of any room because warm air can’t circulate well there – strike four.

There was mold on the baseboard in the very corner of this bathroom.  That space got very cold because of all the strikes against it, and that allowed condensation to form, and that allowed mold to grow.  From experience I know to double check areas that are likely to be quite cold and allow water from condensation.

Mold on the coldest surface of the house due to condensation.

That’s mold.

Plumbing leaks — I use an infrared camera to look for water problems below all the sinks, tubs, and showers after I’ve run a lot of water.  It’s not very common, but I have occasionally seen some pretty dramatic leaks that were only visible with infrared.  Part of the repair process for these types of leaks is to check for mold above the ceiling and behind the wall, and I always make sure my clients are aware how important that is.

So when might mold testing be a good idea?  If you suspect that there’s hidden mold because you can smell it or feel its effects, then it might be time to call in an expert, form a hypothesis about what might be going on, and do some testing to try to confirm that hypothesis.

Fire Sprinkler Systems

Fire sprinkler systems are becoming very common in new construction and major remodel projects, and so here’s a brief primer on residential fire sprinkler systems.

When it comes to enforcing life safety codes in commercial and multi-family buildings, local jurisdictions usually enforce some version of either the International Fire Code (part of the ICC family of codes) or the National Fire Protection Association (NFPA®) document NFPA 101® Life Safety Code®.  But both of these documents refer to NFPA® 13 as the standard for how to install sprinkler systems, so this is the definitive source.  A separate document, NFPA® 13D, applies only to one- and two-family dwellings and manufactured homes.

There are four basic types of water-based fire sprinkler systems.

  1. Wet-pipe sprinkler system – The sprinkler pipes are constantly full of water under pressure. When heat from a fire activates one or more sprinklers then water flows from only those heads until the system is shut off.  The NFPA® reports that with home sprinkler systems roughly 85 per cent of the time only one sprinkler will activate.  This is by far the most common type of sprinkler system in residential settings.
  2. Dry-pipe sprinkler system – The sprinkler pipes are only charged with compressed air, and there’s a dry-pipe valve somewhere not subject to freezing temperatures. When heat from a fire opens a sprinkler the compressed air is released and the dry-pipe valve senses the loss of pressure and opens to allow water flow until the system is shut off.  This type of system is typically used in areas where freezing temperatures are likely to occur, like open parking garages.
  3. Deluge sprinkler systems – This system consists of open sprinklers installed in unpressurized pipes, and a valve at some central location. When some thermally sensitive electronic device senses a fire it sends a signal to open the valve and water pours out of all the sprinklers simultaneously until the system is shut off.  This type of system is usually found in areas where even a small fire could very quickly spread due to the type of materials stored in the area.  This type of system is also often found in the movies – it’s certainly more dramatic to have all the sprinklers go off at once even if it’s not usually an accurate portrayal.
  4. Preaction sprinkler system – This system consists of sprinklers connected to a dry system of pipes. The system will only operate when heat from a fire opens a sprinkler head and also when an electronic device senses a fire and opens the waterflow control valve.  This type of system is usually found where a false activation of the sprinkler system would cause a catastrophic loss, maybe to some irreplaceable contents.

The sprinkler is the device that actually discharges water.  Sprinklers can be installed in any of several configurations, but each configuration requires a different sprinkler design, so they’re not interchangeable.  An upright sprinkler (designed to be installed upward from a branch line) can’t be swapped out for a pendant sprinkler (designed to be installed downward from the branch line) or a sidewall sprinkler (mounted on a vertical wall).  You’re also likely to come across concealed sprinklers which have a removable decorative cover plate that releases at the proper heat level.

The deflector is a small piece of metal on the sprinkler.  The water discharge hits the deflector, creating the discharge pattern.  The design of the deflector is different for the various types of sprinklers in order to create the right type of water spray pattern.

These sprinklers illustrate the differences.  The deflector is shaped differently in these three sprinklers, one pendant (hanging down), one upright, and one sidewall.  These are definitely not interchangeable.

NFPA® 13 defines six temperature categories for sprinklers from Ordinary to Ultra High. “Ordinary temperature-rated sprinklers” have a temperature rating between 135°F and 170°F, and this is what you should expect to see in one- and two-family dwellings.  “Intermediate temperature-rated sprinklers” are rated between 175°F and 225°F.  These are also allowed in most locations, with the exact type required depending on the maximum ambient ceiling temperature.

The temperature rating of the sprinkler should be stamped into it, although it can be very hard to see and I don’t recommend that you try.  They also should be color coded, with Ordinary sprinklers either uncolored or black, and Intermediate sprinklers being white.

The sprinklers shown above have no color so you’d expect them to be in the ordinary range, which they are.

NFPA® is very clear that sprinklers shall only be painted by the manufacturer.  It’s a big problem if any installer or homeowner paints a sprinkler or modifies it in any way.  That sprinkler needs to be replaced.  Also there should never be anything hanging from a sprinkler.

There are three primary heat activation mechanisms for sprinklers, including metal fusible links and chemical pellets.  But for residential sprinklers the most common is the glass bulb.  The bulb is inserted to hold back the sprinkler plug.  At high temperature the liquid in the bulb expands, breaking the bulb and releasing the plug.  Water starts to pour out.  It’s worth noting that mechanical damage can activity a sprinkler also, so be careful.

You should expect to see an orange or red bulb in an Ordinary temperature rated sprinkler (as in the pictures above), and a yellow or green bulb in an Intermediate temperature rated sprinkler.

For residential systems in one-and two-family dwellings, NFPA® 13D does not require that spare sprinklers be provided (section  But for commercial and most multi-family buildings not only are spares required, but a wrench is required, and one spare of each of the various types of sprinklers is required.  But you’ll usually see spare sprinklers and I always tell clients to be sure to have them.

spare sprinklers

It’s likely that you’ll see a waterflow switch and alarm, although it isn’t required (unless the house doesn’t have smoke alarms, in which case you’ve got a different set of problems).  A typical switch will look something like this in the picture below.  When water flows through the system it activates the switch, which in turn should sound a local bell in the same area, and maybe a horn and strobe at the front of the house.

water flow switch

water flow alarm bell

There should be a valve and drain pipe that discharges to a floor drain or sump.  You can test the waterflow alarm by opening this drain valve, but be careful — you might call the local fire department depending on how the alarm is configured.

A backflow device isn’t required by fire sprinkler codes, but your local plumbing code probably requires it so you should look for that and note if it’s missing.

Residential systems have a different design from standard sprinklers and a different discharge water pattern.  Residential systems are designed with more of a goal towards controlling the fire to allow for occupants to evacuate, rather than putting out the fire.  Residential sprinklers spray higher than other types to help prevent flashover conditions.  Flashover is when the environment in a room is changing from two layers (hot on top and cooler on the bottom) to a single layer, well-mixed, with hot gases from floor to ceiling.  This condition isn’t survivable even by a fully protected firefighter, so preventing it is key to allowing occupants to escape.

As with most things home inspectors deal with, sprinklers need to be installed according to their listing, and that pertains to their spacing as well.  Typically you should expect a residential sprinkler to cover a maximum of 144 square feet, so the maximum spacing should be 12 feet.  But some sprinklers are listed to protect larger areas, so without seeing the sprinkler’s specifications you can’t know for sure.

In a one- or two-family dwelling you won’t need sprinklers in bathrooms of 55 square feet or less, or in most smallish clothes closets, or in garages.  You also won’t need a sprinkler in an attic with or without storage, or in a crawl space, or in a concealed space that’s not intended for living purposes.  This is consistent with the philosophy of controlling the fire to let occupants escape.  But you will need a sprinkler in a closet used for HVAC equipment, water heater, or laundry appliances.

Of course no water-based fire suppression system is going to be effective without a good source of water.  NFPA® 13D requires 18 gallons per minute for any single sprinkler, or with two or more 13 gpm.  If you’re using a stored water supply or the house is on well water, the system needs to be able to operate for at least 10 minutes (or seven minutes for some smaller single story houses).  Again, this might not be enough time to control a fire, but it should give occupants enough time to escape.

If there’s any doubt that a house can supply this amount of water, then a good fire protection contractor should evaluate the system and confirm there’s enough water or make the necessary upgrades.  To run at 18 gpm for 10 minutes might require the installation of a 180 gallon storage tank.


Of course the greatest water supply possible can be rendered moot if there’s a valve that’s shut off.  NFPA® 13D requires a single valve to shut off both the domestic water system and the sprinkler system since no homeowner is likely to shut off his sprinkler system and make do without a flushing toilet.  Or if the sprinkler system has its own valve then that valve needs to be either “supervised” by a monitored alarm system, or locked open.  (It’s not clear who’s allowed to hold the key.)  And of course anything that might restrict water flow or decrease pressure needs to be installed so that it won’t interfere with the performance of the fire sprinkler system.

I usually see separate shut off valves, and I always mention to my clients the importance of a working fire sprinkler system and urge them to never shut off the sprinkler system.

It’s easy for a homeowner to overlook a system that he hopes will never operate.  But a properly installed fire sprinkler system can be the difference between life and death.