What Is Floor Raceway Concealment? (Threshold Caps)
Floor raceway concealment places a listed wiring channel beneath or within a compatible threshold-cap assembly, so conductors are protected and the transition looks finished. The cap is trim, not a wiring method. Choose a raceway approved for that floor location, follow its instructions and the locally adopted electrical code, preserve access to required connections, and keep the threshold safe and usable.
A neat floor transition can solve a real wiring problem: a cable must cross a doorway, but a loose cord creates a snag and trip hazard. The challenge is that a cap may look right while concealing an unsuitable raceway or an inaccessible splice. I treat the threshold as a coordinated assembly of flooring, door, cap, raceway, and wiring, not as a cover to improvise after the fact.
Planning: Code, Raceway Listing, and Floor Survey
Floor raceway concealment means routing conductors through a wiring system approved for the intended floor location, then finishing the area with a compatible threshold cap. A decorative cap alone does not protect or authorize wiring. Before choosing parts, confirm the local code, product listing, floor structure, door details, and any accessibility rules that apply.
Start by checking which electrical code edition and amendments your jurisdiction has adopted. The National Electrical Code (NEC) is adopted locally, and requirements may vary by location. Ask the building department or electrical inspector whether a permit or inspection is required. NEC 110.3(B) requires listed or labeled equipment to be installed and used according to its instructions.
Then survey the route before opening the floor. Record the door’s swing, floor heights on both sides, threshold width, floor construction, and where the wiring needs to go. Check for existing electrical, plumbing, heating, or other services. Do not cut or drill structural members, fire-rated assemblies, or concealed services without confirming that the method is permitted.
Select a listed raceway system specifically suitable for the planned floor location and installation method. A surface raceway, an underfloor raceway, and a threshold trim kit are not interchangeable just because their covers fit. NEC Article 390 applies only when the installation qualifies as an underfloor raceway; other wiring methods are governed by their applicable code articles.
Before purchase, review the raceway and cap instructions for:
- Permitted locations and flooring types
- Approved conductors, fittings, and cover fasteners
- Raceway fill limits and conductor bend requirements
- Bonding requirements, where applicable
- How the route is accessed for pulling, inspection, or service
- Whether the threshold cap is approved for use with that raceway
The raceway’s listing and instructions set the limits of the assembly. If the chosen trim does not match the listed system, do not assume that a snug fit makes the combination acceptable. Next step: verify the raceway and cap as a compatible system before planning cuts or buying materials.
Access and Clearances: Door Swing, Threshold Height, and Serviceability
A threshold cap must not block the door or create an unsafe floor transition. Check the complete door movement, including the sweep, latch, and flooring, rather than relying on a generic clearance number. There is no universal raceway-to-door gap; the acceptable fit depends on the actual door and product instructions.
For an accessible door covered by the 2010 ADA Standards, §404.2.5 limits the threshold height to ½ inch maximum above the finished floor. Section 303 sets rules for changes in level: a change of ¼ inch or less may be vertical; a change over ¼ inch and up to ½ inch must be beveled, with a slope no steeper than 1:2. A taller change is not permitted under that section.
These ADA provisions do not automatically apply to every private home. Their application depends on the building’s use and the rules that govern it. Check the applicable accessibility requirements with the local authority or a qualified design professional. Even where the ADA does not apply, a low, stable transition helps reduce trip risk.
Measure the finished assembly, not just the cap. The relevant height is the change between the finished floor and the threshold surface. A cap that sits level on one side can still create an abrupt edge on the other if flooring thicknesses differ.
Also confirm that the cap does not interfere with the door’s full swing, latch, or seal. Test the door with the intended flooring and sweep in place, and follow the door, sweep, flooring, and threshold manufacturers’ instructions. Keep all required junction or pull points accessible. A cover that hides a connection does not make that connection serviceable.
| Check | Measurement or rule | What to confirm |
|---|---|---|
| Accessible-door threshold | ½ in. maximum (12.7 mm) | ADA §404.2.5 applies where required |
| Vertical floor change | ¼ in. or less (6.35 mm) | ADA §303.2 |
| Beveled floor change | Over ¼ in. through ½ in. | Slope no steeper than 1:2 under ADA §303.3 |
| Door clearance | No universal raceway dimension | Test actual door, sweep, cap, and floor |
| Raceway access | Product and code dependent | Keep required connections and access points serviceable |
Next step: lay out the cap and raceway in place, then verify the finished elevations and door operation before installation.
Execution: Raceway, Conductors, and Threshold-Cap Installation
Installation starts with the approved wiring system, not with cutting a channel to fit a trim piece. Follow the raceway listing, manufacturer’s instructions, and locally adopted code for its support, fittings, conductors, bonding, and access. If the proposed route requires an unapproved modification, stop and select a compliant system or route.
A careful sequence reduces rework:
- Mark the route. Confirm the destination, cap position, door swing, and floor elevations. Locate known services and check the proposed work area for concealed utilities.
- De-energize affected circuits. Follow safe work practices and verify the circuit is de-energized with suitable test equipment. If you cannot identify or safely isolate the circuit, use a qualified electrician.
- Prepare the floor only as allowed. Do not notch structural framing or penetrate a rated assembly unless the design and applicable rules allow it. Use only the opening and mounting method specified for the raceway.
- Fit and support the raceway. Use listed fittings and the stated fasteners. Do not bend, cut, or alter the raceway or cap unless the instructions permit that specific change.
- Install conductors and fittings. Use the conductor type, fill, bend radius, and separation required for that system and code. Complete bonding where required.
- Close the assembly with the approved cap. Fasten it as directed, without pinching conductors or covering a connection that must remain accessible.
- Test and document. Complete required electrical checks and inspections. Retain access to any required junction box or pull point.
Do not place an extension cord, flexible cord, or unlisted cable beneath a threshold cap as a substitute for an approved wiring method. Do not bury a splice or modify a listed assembly unless both the product instructions and applicable code expressly allow it.
A common edge case is a cap that appears flush over a raceway not listed for floor use. Another is a hidden splice that cannot be reached for service. Neither problem is solved by the neat appearance of the finished trim. Next step: if the listing, wiring method, or access rules are unclear, resolve them before closing the floor.
Verification: Accessibility, Electrical Inspection, and Operation
Verification checks both the hidden wiring system and the visible walking surface. A finished cap must fit its listed raceway, protect the conductors, and leave required connections accessible. The completed threshold must also meet applicable height and bevel rules, and the door must work through its full range.
After installation, inspect the cap for movement, raised edges, gaps, or fasteners that project above the walking surface. Measure the floor change at the finished surfaces. Where ADA rules apply, compare the result with the limits in §§303 and 404.2.5; do not rely on appearance alone.
Operate the door slowly through its full swing. Confirm the door clears the cap, closes and latches, and works with its sweep or seal. Check that the cap does not shift under normal use. If the door binds or the transition exceeds an applicable limit, correct the assembly rather than trimming a listed part without permission.
For electrical verification, follow the code, product instructions, and inspection requirements for the wiring method. Confirm that covers are secured, bonding is complete where required, and all necessary junction or pull points remain accessible. Keep product instructions, circuit information, and inspection records with the building documentation.
Typical installation scenarios
These are planning examples, not reports of specific completed jobs. They show how the same threshold problem can lead to different compliant choices.
| Scenario | Main constraint | Appropriate decision |
|---|---|---|
| New flooring at an interior doorway | Finished height can be planned before trim is fitted | Choose a listed raceway and matching cap, then set flooring and threshold elevations together |
| Retrofit across an existing doorway | Floor structure and concealed services may limit the route | Survey first; use only a permitted installation method and avoid unapproved cuts |
| Accessible route through a doorway | Threshold height and bevel rules may apply | Measure finished floor levels and confirm applicable ADA and local requirements |
| Existing cap with an added cable | Cap may not be part of a listed wiring system | Do not tuck in a cord; select an approved wiring method and preserve service access |
Next step: have the electrical work inspected where required, then recheck the cap and door after the floor finish is complete.
Conclusion and FAQ
A threshold cap is a finish component, not permission to conceal any cable beneath it. Safe floor raceway concealment depends on a raceway listed for its location, installation that follows its instructions and the adopted code, accessible connections, and a threshold that works with the door and finished floor. Measure the completed transition and verify the assembly before closing it.
Frequently asked questions
What is floor raceway concealment?
It is routing wiring through an approved raceway at a floor crossing, then covering or finishing it with a compatible threshold assembly. The raceway, not decorative trim, provides the wiring method.
Can I hide a cable under a threshold cap?
Only if the wiring system is approved for that location and installed as its listing and the local code require. Do not conceal extension cords, flexible cords, or unlisted cable under a cap.
Is a threshold cap an electrical raceway?
Not by itself. A cap is commonly a trim or cover part. It serves as part of a wiring system only when the product documentation identifies and permits that use.
Does NEC Article 390 apply to every floor raceway?
No. Article 390 applies where the installation qualifies as an underfloor raceway. Other raceway types fall under their applicable NEC articles and product instructions.
What is the maximum accessible-door threshold height?
Under 2010 ADA Standards §404.2.5, the threshold may be no more than ½ inch high where that standard applies. Check local rules and the building’s accessibility requirements.
How should a floor-level change be beveled?
Under ADA §303, a change over ¼ inch and up to ½ inch must be beveled with a slope no steeper than 1:2. A change of ¼ inch or less may be vertical.
Is there a standard clearance between the cap and a door?
No universal raceway-to-door clearance is specified here. Check the actual door, sweep, flooring, and cap instructions, then test the full swing, closure, and latch.
Can a splice be hidden beneath the cap?
Not merely because the cap covers it. A trim cover does not make an inaccessible connection acceptable. Follow the adopted code and raceway instructions, and keep required junction or pull points accessible.
Can I cut a raceway or threshold cap to make it fit?
Only when the product instructions and applicable code allow the specific modification. An unapproved cut can affect the listed assembly, fit, or conductor protection.
Should I hire an electrician?
Use a qualified electrician if you are unsure about circuit isolation, conductor choice, raceway classification, bonding, or code requirements. Follow local permit and inspection rules.
(This article was written by one of our staff writers, Garrett Vance. Visit our Meet the Team page.)
