90.5 - How to Speak NEC: Your Rosetta Stone for Code Language

The Plain Truth

Alright, listen up. Before you go diving into 900+ pages of the Code Book looking for answers, you need to understand how this thing talks to you. Section 90.5 is basically your decoder ring for NEC-speak. Think of it like this: the Code uses three different tones of voice, and if you can't tell them apart, you're gonna get smoked on your exam—or worse, fail an inspection because you thought something was optional when it was actually mandatory.

Here's the deal:

SHALL and SHALL NOT = The Boss Is Talking

When you see "shall" or "shall not," that's not a suggestion—that's your foreman telling you exactly how it's gonna be done, and there's zero wiggle room. "You shall torque those lugs to spec" means DO IT. "You shall not run Romex in a commercial kitchen" means DON'T EVEN THINK ABOUT IT. These are mandatory rules. Break 'em and you're buying the inspector lunch while you rip it all out.

SHALL BE PERMITTED and SHALL NOT BE REQUIRED = Options on the Table

This is the Code saying, "Hey, you've got choices here." When it says something "shall be permitted," it means you can do it that way if you want—it's legal, it's allowed, nobody's gonna red-tag you. "Shall not be required" means you don't have to do something, but you still can if it makes sense for your installation. These are permissive rules—your hall pass to use alternative methods.

Informational Notes and Annexes = The Helpful Apprentice Whispering in Your Ear

See those little "Informational Note" sections or those annexes in the back? That's bonus content—helpful hints, cross-references, calculations, examples. BUT HERE'S THE KICKER: None of that stuff is enforceable. An inspector can't fail you for not following an informational note. It's like the difference between OSHA requirements and the safety suggestions in your tool catalog. Nice to know, but not the law.

Those brackets with references like [NFPA 70E: 130.5(C)]? Just showing you where they copy-pasted text from another standard. Good for research, useless for compliance.

And those informative annexes in the back? They're like the director's commentary on a DVD—interesting if you're into it, but you don't need 'em to pass the test or wire a building.

Key Takeaways (The Stuff You Better Remember)

"SHALL" = MANDATORY – You must do it. No exceptions, no excuses. This is the law according to the NEC.
"SHALL NOT" = PROHIBITED – Don't even think about it. This is explicitly forbidden.
"SHALL BE PERMITTED" = ALLOWED – You can do it this way if you want. It's one acceptable method among possibly several.
"SHALL NOT BE REQUIRED" = OPTIONAL – You don't have to, but you can if it suits your installation.
Informational Notes = NOT ENFORCEABLE – Helpful background info, but an inspector can't cite you for ignoring it.
Informative Annexes = NOT ENFORCEABLE – All that stuff in the back (Annex A, B, C, etc.) is reference material only. Study it for understanding, but it's not code law.
Bracketed references like [NFPA 72: xxx] – Just showing the source of extracted text. Informational only.
References without dates – Use the edition listed in Informative Annex A (basically tells you which version of other standards the NEC is referencing).

Real-World Jobsite Scenarios

Scenario 1: The "I Thought It Was Optional" Disaster

You're wiring a commercial kitchen. You read 422.16(B)(2) that says "GFCI protection shall be provided" for commercial cooking appliances. Your buddy says, "Nah, I've seen kitchens without it." You skip it thinking it's a suggestion.

Inspector shows up: RED TAG.

Why? Because "shall be" means MANDATORY. Not optional. Not negotiable. Your buddy's old jobs? Either they were grandfathered, or they were wrong too. Cost you a day and a trip back to the supply house. Know your "shalls."

Scenario 2: The Permissive Rule Saves Your Bacon

You're roughing in a residence and need to run some NM cable through a wall that also has some plumbing. Code says you need to keep 1-1/4" from the edge of the stud OR use a steel plate for protection (300.4). That "or" is key—it's giving you options. The Code "permits" either method.

The layout is tight, you can't keep the distance, so you grab your steel plates. Inspector comes through, sees the plates, checks off the box. You kept moving because you understood you had permitted alternatives.

Scenario 3: The Informational Note That Isn't Gospel

You're installing a residential service and you see an Informational Note under 230.70(A) that suggests mounting the disconnect at a certain height for convenience. Your customer is 6'5" and wants his disconnect higher than typical. Inspector questions it.

You pull out the Code: "That's an informational note, not a requirement. The actual rule just says 'readily accessible.' At 6'5", this height IS readily accessible for the homeowner."

Inspector nods, moves on. You didn't get trapped into treating a suggestion like a rule.

Scenario 4: The Exam Question That Tests This Exact Concept

Multiple choice: "According to the NEC, when a rule uses the term 'shall be permitted,' it means the action is:"

A) Required in all cases
B) Prohibited unless approved
C) Allowed but not required ✓
D) Only for residential installations

You nail it because you know 90.5(B) cold. That's two points toward your journeyman ticket right there.

What to Study (Exam Prep Gold)

If you're preparing for any level of licensing exam, here's what the test-writers LOVE about 90.5:

High-Priority Exam Topics:

Differentiating SHALL from SHALL BE PERMITTED
- Expect questions that give you a code section and ask whether it's mandatory or permissive
- Example: "Section XYZ says 'shall be permitted'—is this required?" (Answer: No, it's optional)
Enforceability of Informational Notes
- Classic trap question: "Can an inspector require compliance with an Informational Note?" (Answer: NO)
- They LOVE this one because it separates people who actually understand code structure from those just memorizing
Status of Informative Annexes
- "Are Informative Annexes enforceable parts of the NEC?" (Answer: Nope, information only)
- Annex D (Examples) is super helpful for learning, but you can't be cited for not following it
Understanding bracketed references
- Less common, but they might ask what those [NFPA XX: xxx] brackets mean
- Answer: Source reference for extracted text, informational only

Study Tips:

Make flash cards: Front: "SHALL" / Back: "MANDATORY REQUIREMENT"
Practice identifying: Grab random Code sections and highlight the "shalls" vs. "shall be permitted"—train your eye
Read a few Informational Notes and ask yourself: "Could I be cited for ignoring this?" (Answer is always no)
Memorize this hierarchy: Mandatory Rules > Permissive Rules > Informational Material (in order of enforceability)

Typical Exam Question Formats:

"The term 'shall' in the NEC indicates...?" (Answer: Mandatory requirement)
"When the Code uses 'shall be permitted,' it means...?" (Answer: Allowed but not required)
"Informational Notes are...?" (Answer: Not enforceable)
"True or False: Informative Annexes are mandatory." (Answer: False)

Real Talk:

On your exam, you might see 3-5 questions directly from Article 90, and at least one or two will test whether you understand mandatory vs. permissive language. That's easy points if you've got 90.5 down cold. Don't overthink it—the NEC is actually trying to be clear here. They're literally telling you how to read the book.

The Bottom Line (Your Tailgate Talk Takeaway)

Look, the NEC is written in a specific language, and 90.5 is your crash course in speaking it. Master this section and you'll move through the Code Book faster, understand what's actually required vs. what's just nice-to-know, and avoid those gut-punch moments when an inspector fails something you thought was optional.

Three-word summary? SHALL MEANS DO.

Everything else is either "you can if you want" or "here's some helpful info." Keep that straight, and you're already ahead of half the people taking the test.

Now get back to work—but make sure you shall do it right! 🔧⚡