A rough-in electrical inspection examines the wiring, the boxes and the conductors while the wall is still open, and nothing else. It does not inspect your switches, your plates or your finishes, because none of those are in the wall yet. Here is what is on the list, what is not, and which decisions stop being reversible that day.
In short
- A rough-in inspection looks at boxes, cable, support, free conductor length, grounding and the presence of a neutral. It is about the cavity, not the hardware.
- The trigger is concealment. One state rule puts it plainly: all wiring must be inspected before it is concealed, and whoever closes the wall early pays to open it again.
- Devices and plates are not installed at rough-in. One municipal checklist forbids installing them before the rough-in is approved.
- Six figures get measured more than anything else: 6 inches of free conductor, 1/4 inch of cable jacket inside the box, 12 inches to the first staple, 4 1/2 feet between staples, 1 1/4 inches of wood in front of the cable, and 1/16 inch of steel nail plate where that cannot be met.
- Three decisions become expensive after that day: gang count, box depth, and whether a grounded conductor exists at the switch location.
What a rough-in electrical inspection is
A rough-in electrical inspection is the inspection of everything about to become invisible, carried out after the wiring is installed and before any insulation, drywall or finish covers it.
The clearest definition in American regulation is not in a model code but in a state rule. Minnesota titles the requirement Rough-In Inspection of Wiring to Be Concealed, and it works by notice rather than by checklist: where wiring is to be concealed, the inspector must be notified far enough in advance to permit completion of a rough-in inspection before concealment, and the notice period excludes Saturdays, Sundays and holidays. The inspection is defined by what is about to happen to the wall, not by a list of items.
Why the inspection exists: the wall is about to close
Every rough-in requirement follows from one fact: after this inspection the work becomes unreachable without destroying finished surfaces.
The model codes say so in those terms. The 2015 IRC and IBC, as adopted and published by the City of Groton, Connecticut, state that work “shall not be done beyond the point indicated in each successive inspection” without approval, that nonconforming parts “shall be corrected”, and that work “shall not be covered or concealed until authorized by the building official”. The same text requires the result, pass or fail, to be “made in writing by the building official”. We took the failure case apart separately in what happens when you fail an electrical inspection, and the document itself in how to read an electrical inspection checklist.
Who must be notified, and who pays if the wall closes first
The cost of closing a wall before the rough-in inspection falls on whoever closed it, and at least one state says so explicitly.
Under the Minnesota rule, if wiring is concealed before the rough-in inspection without adequate notice, the person responsible for having enclosed the wiring is responsible for all costs of uncovering it and replacing the cover material. The City of Saint Paul residential rough-in checklist, revised July 2023 against the 2023 NEC, repeats both points at the top of the page: all wiring must be inspected before it is concealed, and the party who concealed it carries the removal and replacement cost. That is the practical reason a drywall crew does not get ahead of an electrical inspector.
What the inspector actually measures
Most of a rough-in inspection is a small number of published dimensions checked repeatedly, box after box.
| What is checked | The figure | Code reference |
|---|---|---|
| Free conductor at each box, grounding conductor included | At least 6 inches | NEC 300.14 |
| Cable jacket secured to the box | Jacket extends at least 1/4 inch inside | NEC 314.17(C) |
| First support after a box | Within 12 inches, and no more than 18 inches of unsupported cable | NEC 334.30 |
| Support interval along a run | No more than 4 1/2 feet | NEC 334.30 |
| Cable set back from the face of a stud or joist | At least 1 1/4 inches | NEC 300.4(A) and (D) |
| Steel nail plate where that set back is impossible | At least 1/16 inch thick | NEC 300.4(D) |
| Box volume against conductors and devices | Marked cubic inch capacity on nonmetallic boxes | NEC 314.16 |
| Box fixing | Rigidly secured to the structure | NEC 314.23 |
| Ceiling box used for a luminaire | Listed to support up to 50 pounds | NEC 314.27(A) |
| Ceiling box where a paddle fan is or may be fitted | A listed fan box, not a luminaire box | NEC 314.27(C) |
| Unused openings in a box | Closed, and a punched out nonmetallic box replaced | NEC 110.12(A) |
| Box set back in a noncombustible surface | Not more than 1/4 inch, and no tolerance in a combustible surface | NEC 314.20 |
Circuit layout is checked at the same visit, which surprises people who expect it at final. The Saint Paul list runs through receptacle spacing at 6 feet along a habitable wall and any wall space 2 feet or wider, countertop receptacles no more than 24 inches from any point and one per counter space 12 inches or wider, an island receptacle at or up to 20 inches above the counter and never below it, a bathroom receptacle within 3 feet of the sink edge, no receptacle within 3 feet horizontally and 8 feet vertically of a shower threshold, and lighting load at 3 VA per square foot, so a 15 A circuit covers roughly 600 square feet. Circuit capacity itself we treat in how many outlets can be on one circuit, while the boxes themselves are in electrical box types and sizes. One caution on that checklist, in its own words: it is a guideline and does not contain every 2023 NEC requirement.
What a rough-in inspection does not cover
Nothing you chose for appearance is inspected at rough-in, because none of it is installed, and on some jobs installing it early breaks the inspection sequence.
| Item | Looked at during rough-in? | Where it is actually looked at |
|---|---|---|
| The box, the cable, the conductors | Yes, this is the entire inspection | Rough-in |
| Switch and outlet devices | No, they are not installed yet | Final electrical |
| Wall plates and cover plates | No | Final electrical, under OSHA 1910.305(c)(4) wording about seating against the finished surface |
| Finish, colour, brass or stainless | No, and no inspector has an opinion on it | Nowhere, it is not a code matter |
| Luminaires and fans | Only the box that will carry them | Final electrical |
| Insulation around recessed luminaires | Yes, at least 3 inches clear unless the fixture is Type IC | Rough-in, NEC 410.116(B) |
| Device listing and certification marks | Not on the device, which is absent | Final, and see our certification articles |
| Framing and fireblocking | No, a different trade and a different visit | Framing inspection, after rough-in passes |
Two things follow. The first is that a plate requirement is a finished surface requirement: 29 CFR 1910.305(c)(4) requires snap switches mounted in boxes to “have faceplates installed so as to completely cover the opening and seat against the finished surface”, and at rough-in there is no finished surface to seat against. The second is that certification is a device question, not a cavity question, which is why verifying a certification mark and getting unlisted or imported equipment approved both belong to a later stage of the job than this one.
The grounded conductor at the switch box, and why our dimmer does not let you skip it
A grounded conductor, which almost everyone calls the neutral, is required at lighting switch locations serving habitable rooms, and whether one exists is settled at rough-in and nowhere else.
The requirement is NEC 404.2(C), and the Saint Paul rough-in list carries it as a line item. Keith Lofland, writing for IAEI Magazine in 2018, explains both the rule and the reason: the conductor is required at switch locations controlling lighting loads on a grounded general purpose branch circuit, and the 2011 intent was to end up with “no current being intentionally introduced onto the equipment grounding system” by electronic switching devices. He also tracks the exception list from seven recognised conditions in 2014 to five in 2017, and notes a retrofit allowance for replacement switches in locations predating local adoption of 404.2(C), capped at not more than five electronic control switches on a branch circuit.
This is where our own hardware meets the rule, and the honest answer is uncomfortable in a useful way. The Studio Timeless TRIAC dimmer module has two conductors, INPUT and LAMP, and requires no neutral at the box. That is a real advantage in an old house. It does not exempt the rough-in from 404.2(C): the code asks whether the conductor is present at the location, not whether the device you happen to buy will use it, so a new build that leaves the neutral out because the chosen dimmer does not need one has still failed a line on the checklist. A house with no grounding conductor at all is a different problem, and that one is in upgrading switches with no ground wire, with cable types in two wire against three wire boxes.
Box depth: the one rough-in figure we do not publish
Box depth is fixed at rough-in and cannot be changed afterwards without opening the wall, and we publish no required depth for our own pieces.
That is worth stating rather than leaving a builder to find out. A competitor we examined on October 25 publishes a recommended box depth of 2 inches and a device projection of 1 3/8 inches for its wall dimmer, as recorded in our look at that range. We publish neither figure for our rotary dimmers or our knurled toggles. A Studio Timeless piece is a single machined unit rather than a plate bought separately from a device, which changes the depth question without removing it, because the module still has to sit inside whatever box was nailed to a stud months earlier. Until we publish a minimum depth, the safe instruction is the general one: specify a deeper box than your box fill calculation strictly requires, and if a particular piece is already chosen, ask us before the boxes go in. We will not confirm a fit from a photograph, and we will not confirm compatibility with another manufacturer’s equipment without written confirmation from that manufacturer.
Gang count is framed at rough-in, not chosen at checkout
The number of positions in a switch bank is a framing decision, so it is effectively locked by the rough-in inspection even though no switch is present.
A four position bank needs a four gang box, and that box is nailed between studs before any drywall goes up, so going from three positions to four afterwards means opening the wall. Two range limits are worth knowing before the box is chosen. Our knurled toggle switches run from 1 to 4 gangs and the Retro Toggle does the same, while rotary dimmers reach 5, and no 6 gang plate exists in any style. The full ceiling is in the 5 gang and 6 gang article. And circuits, not positions, decide the dimmers: one lighting circuit takes one TRIAC dimmer, so a second control point on that circuit is a 3 way toggle and not a second rotary dimmer. A 0-10V controller never interrupts the 120 V line and needs its own switch beside it, so it takes two positions in the box rather than one. That is in the 0-10V and PWM article, with the dimming background in the rotary dimmer pillar. A fan motor never goes on a lighting dimmer at all.
Free conductor, jacket, support and pigtails: what fails most often
The items that fail a rough-in are overwhelmingly the cheap ones, which is why they are worth checking before the inspector arrives.
Six inches of free conductor at every box, grounding conductor included. A quarter inch of cable jacket inside the box, which means the sheath is stripped at the right place and not at the connector. Twelve inches to the first staple, then no more than four and a half feet between staples. An inch and a quarter of wood in front of the cable, or a nail plate. Unused openings closed. And the one missed most often: where several equipment grounding conductors arrive in one box they must be spliced with a pigtail to the device grounding terminal under NEC 250.148, and Saint Paul states that this has to be done before the inspection is scheduled rather than on the day. Wiring methods themselves are in how to wire a light switch, and the related question of plaster walls on an older house in removing a wall plate on plaster.
Where rough-in sits in the sequence
Rough-in is a position in a queue, and it gates the trades that come after it.
The City of Minneapolis guide to calling for inspections makes the dependency concrete: the framing inspection requires that all rough-in plumbing, heating and electrical inspections have been approved first, and rough-in plumbing and mechanical must happen before covering or concealment and before fixtures are set. The same document notes that in Minnesota electrical permits and inspections are issued by the State rather than the city, so two offices sit in one job. Who may do the work and who must declare it are separate questions, separated in do you need a permit and a licensed electrician.
How to prepare for a rough-in electrical inspection, step by step
Preparation is making the work visible and pre checking the figures that get measured, and it takes about an hour.
- Confirm the permit is open and you are calling the right stage. Check that the permit covers the work and that you are booking the rough-in and not the final. In some states the electrical permit sits with a different office from the building permit, so confirm which one schedules it.
- Give notice in the window your jurisdiction requires. Notice has to be early enough to allow the inspection before concealment, and weekend days and holidays may not count toward it. Book before the drywall crew is scheduled, not after.
- Leave everything visible. No insulation in the bays being inspected, no drywall, no box covered by anything. If a bay has to be insulated early, raise it before the visit rather than hoping it passes.
- Walk the six figures yourself, box by box. Six inches of free conductor including the grounding conductor, a quarter inch of jacket inside each box, twelve inches to the first support, four and a half feet maximum between supports, an inch and a quarter of wood in front of each cable or a nail plate, and every unused opening closed.
- Splice and pigtail the grounding conductors before you call. Where several equipment grounding conductors meet in a box, splice them and run a pigtail to the device grounding terminal. One published municipal checklist requires this done before the inspection is scheduled.
- Check that a grounded conductor exists at every lighting switch location that needs one. NEC 404.2(C) asks whether the conductor is present, not whether your chosen device will use it. A dimmer that needs no neutral does not remove the requirement.
- Count gangs and match the box to the device you intend to buy. Confirm the box width matches the number of positions and that the box is deep enough for the unit you plan to install. This is the last moment either can be changed cheaply.
- Keep the written result with the job file, and do not close the wall until it says you may. The model codes require the result in writing and prohibit covering or concealing the work until the building official authorises it. A verbal pass from anyone is not that authorisation.
If you fail, and if you covered it anyway
A failed rough-in is a correction notice and a reinspection. A wall closed without one is a different and more expensive conversation.
On a failure the model codes require written notice of what does not comply, require nonconforming parts to be corrected, and prohibit covering the work until the building official authorises it. The mechanical code text defines reinspection as corrections made and the work then resubmitted to the code official for inspection and testing. No model code sets a reinspection fee, a correction deadline or a maximum number of failures, so all three are local. Full treatment, including the wall that is already closed, is in what happens when you fail an electrical inspection.
Safety, and when this stops being a homeowner job
Rough-in work is new wiring in an open wall, and the hazard is not the open wall but anything in it already live.
Before touching any conductor, switch off the breaker that feeds it and then verify the absence of voltage with a measuring instrument rather than trusting the panel label. A dead circuit is one you have tested, not one you have switched off. Two separate questions then decide whether this is yours to do at all: whether your state allows you to perform the work, and whether your jurisdiction requires a permit and inspections for it. New circuits, service work, panel changes and most new construction require a licensed electrician and a permit in most places, and a rough-in inspection only exists because a permit was issued. Local code and your authority having jurisdiction govern, not this article and not a manufacturer page. If a wiring question remains open, our installation and compatibility guide is the right place for it, and we do not confirm a wiring compatibility without written confirmation from the equipment manufacturer.
Rough-in electrical inspection: questions we are actually asked
What is a rough-in electrical inspection?
It is the inspection of wiring, boxes and conductors carried out after the electrical is installed and before insulation, drywall or any finish covers it. Minnesota titles its rule Rough-In Inspection of Wiring to Be Concealed, and that is the definition: the trigger is concealment.
What has to be finished before a rough-in inspection?
All cable run and supported, all boxes mounted and sized, conductors left long enough, unused openings closed, and equipment grounding conductors spliced and pigtailed. One municipal checklist requires the pigtails done before the inspection is even scheduled.
Can I install switches and outlets before the rough-in inspection?
Normally no, and on some jobs it breaks the sequence. The devices are not what is inspected, they hide the conductors, and one published municipal checklist prohibits installing wiring devices before the rough-in is approved. Check your own jurisdiction.
Does insulation have to be out for the rough-in inspection?
Yes for the bays being inspected, because the point is that the wiring is visible. Separately, thermal insulation must stay at least 3 inches clear of a recessed luminaire unless it is a Type IC fixture, and that clearance is checked at rough-in.
How much free wire has to be left in each box?
At least 6 inches of free conductor at every box, measured from where the conductor emerges, and the equipment grounding conductor counts. That is NEC 300.14, and it is probably the single most measured figure of the visit.
Do I need a neutral at every switch box?
A grounded conductor is required at lighting switch locations serving habitable rooms, bathrooms, hallways and stairways under NEC 404.2(C), with a short list of exceptions and a retrofit allowance for existing locations. The rule asks whether the conductor is present, not whether your chosen dimmer will use it.
What happens if the drywall goes up before the rough-in inspection?
The wall comes back off, and the cost falls on whoever closed it. The Minnesota rule makes the person responsible for having enclosed the wiring responsible for all costs of uncovering it and replacing the cover material.
Is a rough-in inspection the same as a framing inspection?
No, and the order matters. The Minneapolis guidance requires all rough-in plumbing, heating and electrical inspections approved before the framing inspection, so rough-in is a gate framing waits behind.
How long does a rough-in electrical inspection take?
No model code sets a duration and we will not invent one. It depends on the size of the job and the jurisdiction, and the only part under your control is how much of the checklist you walked before the inspector arrived.
Does my choice of brass switch affect the rough-in?
Not the finish, and not the brand. Three things do: the number of positions, which fixes the gang box; the box depth, which fixes what will physically fit; and whether a grounded conductor reaches the switch location. Everything decorative is decided later and changed easily.
What this means for a brass hardware order
The rough-in inspection never looks at a brass switch, and it still decides whether the one you want can be installed. Positions, box depth and the presence of a neutral are settled with the wall open; finish, accent and engraving are settled later and cost nothing to change. So order samples whenever you like, and settle the gang count and the box before the drywall is booked. Studio Timeless builds solid brass switches, dimmers and outlets as single machined units for the United States market, which makes box depth worth asking us about early. The switches and outlets collection and the outlet range are where to start, the specification article published alongside this one covers how to write the decision down, and the duplex and GFCI pages carry the figures for the positions a rough-in is mostly made of. Installing a GFCI afterwards is a separate procedure and it is in how to install a GFCI outlet.
Last updated: October 26, 2026
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