A customer wants the desk on the far side of the room wired, today, with no holes in the wall. The flat cord in the van would slide under the rug and through the door gap, and the round cord would not. The flat vs round ethernet cable decision is about where the cable lives and what it has to survive, not about speed.
Is flat or round Ethernet cable better?
Round cable is the default: its twisted pairs are cabled together inside a jacket that protects the twist, and installed cable is listed and marked for the space it runs through. A flat cord is a short, stranded patch cord for places a round one will not fit, such as a door gap or along a baseboard. Keep flat cords out of walls and permanent links.
How flat and round Ethernet cables are built
Both carry four twisted pairs. The difference is how those pairs sit inside the jacket.
- Round cable: the four pairs are twisted around each other into a core, often with a separator between them, inside a round jacket.
- Flat cable: the pairs lie side by side in a thin, wide jacket. Consumer explainers note that this side-by-side layout limits how tightly the pairs can be twisted, and that most flat cords have little or no shielding.
The twist is not decoration. The Clemson University communications cabling standard states that UTP cable is protected from crosstalk and EMI through the pair twist and lay configuration, which is why it sets a minimum bend radius of 4 times the cable diameter for copper patch cords. A crushed jacket or cramped layout eats into that protection.
Flat vs round ethernet cable compared
| Point | Flat cable | Round cable |
|---|---|---|
| Pair layout | Pairs side by side in a wide jacket | Pairs cabled together in a round core |
| Usual form | Finished patch cords in set lengths | Bulk cable on reels and finished cords |
| Crush resistance | Thin jacket, easily pinched or abraded | Thicker jacket protects the pair geometry |
| Fits through | Door gaps, under rugs, behind furniture | Conduit, walls, ceilings, raceway |
| In-wall and permanent links | No | Yes, with the right jacket rating |
For the conductor and category choices that sit underneath either shape, see stranded vs solid Ethernet cable and Cat6 vs Cat6a.
Are flat ethernet cables slower?
Not by design. Speed comes from the category the cord actually meets, not from its shape. A flat cord that genuinely passes the Cat 6 tests carries the same link speed as a round Cat 6 cord of the same length; forum users who swapped one for the other report no difference on gigabit links.
The catch is “genuinely”. A category printed on a flat cord is a claim, and looser twist control and a thin jacket leave less crosstalk margin. Users report that a marginal cord tends to drop the link outright rather than slow down. Clemson requires all patch cords to be certified by the manufacturer to match the horizontal cable, and the same test suits a flat cord: buy one certified to a stated category that matches the run.
If a link misbehaves after a flat cord goes in, test it rather than guess. Our guide on how to test an Ethernet cable covers wiremap checks and what a certifier adds.
Flat ethernet cable under carpet and through door gaps
This is the job flat cords exist for: crossing a room or doorway where a round cord would make a bump or catch the door. It works for a short patch to a desk or console, but integrators on trade forums are blunt about the risks.
- Foot traffic and furniture. A chair leg or a heavy cabinet on the cord crushes the jacket and disturbs the pairs. Route it where nobody walks, or under a cord cover.
- Feel and trip risk. Under thin carpet the cord can be felt underfoot. Tape the edges of a rug run so it cannot shift.
- Door gaps. Run the cord on the hinge side, where the door does not sweep over it, and check that the door closes without pinching it.
- Warranty. Experienced installers advise telling the customer, in writing, that a cord under carpet is a temporary fix and will not be covered when it fails.
Permanent under-carpet cabling is a different product. The National Electrical Code has a separate type, CMUC, for undercarpet communications wire and cable, listed as suitable for use under carpet. An ordinary flat patch cord carries no such listing.
Why flat cable stays out of walls and permanent links
The cable in the wall is the permanent link, and it has rules a patch cord does not meet.
- Listing and marking. The State of New Mexico telecommunications cabling standard requires all installed cable to be UL listed and to display markings showing the type of installation it is approved for, referencing NEC Article 800. Check the jacket print: a cord without a listing for the space it passes through does not qualify, whatever its shape.
- Jacket rating for the space. Clemson requires horizontal cable to be rated to match the environment, plenum or PVC. A riser or air-handling space needs the ratings set out in our CMR vs CMP cable guide.
- Conductor type. Horizontal runs are solid copper terminated on punch-down jacks. Patch cords, flat or round, are stranded; both standards above require stranded conductors in cords.
PoE and heat in thin conductors
Power over Ethernet sends current down the data pairs, and thinner copper has higher resistance, so it makes more heat at the same current. Check the conductor gauge printed on the jacket before powering a camera or access point through a slim cord: if it is finer than the horizontal cable, it runs warmer.
- Keep PoE cords short and loose, not coiled tight or buried under a rug where heat cannot escape.
- Avoid copper clad aluminum cords entirely; our CCA vs pure copper Ethernet cable guide works through the resistance and heat.
- For high-power devices, use a round cord of the same category as the run. Power planning is in our PoE budget for IP cameras guide.
Length limits for flat cords
A flat cord is a patch cord, so it counts toward the cord allowance of the channel. Clemson caps copper horizontal cable at 90 meters (295 ft) from the outlet to the patch panel, measured along the route with every rise, drop and bend. The cords at each end make up the rest of the channel, and their total length is capped too.
| Location | Flat cord | Round cord | Note |
|---|---|---|---|
| Desk or console patch | Fine | Fine | Factory made, stranded |
| Under a rug, short run | Acceptable | Makes a bump | Temporary; tell the customer |
| Door or window gap | Acceptable | Gets pinched | Hinge side only |
| Inside walls or ceilings | No | Yes | Solid bulk cable, listed for the space |
| Heavy PoE device | Avoid | Preferred | Check gauge and category |
Where to find patch cords and bulk cable
The finished cables category lists factory-made cords, and the bulk wire category covers cable for permanent runs, both in the wire, cable and connector division. For pricing and availability, ask your sales representative through the Bursma contact page or the Grand Rapids area branch, or open a Bursma dealer account.
Frequently asked questions
Can flat Ethernet cable go inside a wall?
It should not. In-wall cable is the permanent link: solid conductors, listed and marked for the space, terminated on jacks. Flat cords are stranded patch cords without that listing.
Is flat Ethernet cable as good as round for gaming or streaming?
For a short cord that genuinely meets its category, yes. Speed depends on the category, not the shape. If the link drops or renegotiates, test or replace the cord.
Can I run PoE over a flat Ethernet cable?
Low-power devices on a short, loose cord are usually fine. For higher power, use a round cord with full-size copper conductors, and never a copper clad aluminum one.
How do I protect a flat cable under carpet?
Keep it out of walkways and from under furniture legs, and use a cord cover where people step. Treat it as temporary.