Run Ethernet Through Walls

Choosing the Right Cable

The cable you put inside the wall today will be there for decades. Choosing correctly now avoids a costly re-pull later.

• Cat6, solid copper, in-wall rated (CMR or CMP) — the correct default for almost all residential runs. Solid conductors perform better than stranded over long distances and terminate cleanly into keystone jacks. Cat6 supports Gigabit Ethernet to 100 m and 10GbE to about 55 m.
• Cat6a, solid copper, in-wall rated — necessary if you specifically need 10GbE beyond 55 m. Cat6a is significantly thicker (typically 8–9 mm diameter vs 6–7 mm for Cat6), harder to fish through tight bends, and costs roughly twice as much. For most homes, Cat6 is sufficient for the foreseeable future.
• Jacket type — plenum (CMP) vs riser (CMR) vs PVC — building codes determine which jacket is required. Plenum spaces (return-air ceilings, raised floors used for HVAC airflow) require CMP-rated cable because its jacket does not produce toxic smoke in a fire. Riser spaces (vertical shafts between floors) require at minimum CMR. Walls in most residential construction accept CMR. PVC-jacketed cable should not be used in-wall in any commercial or code-inspected installation.

Tools You Need

• Stud finder — locate studs and avoid drilling through them unintentionally. Electronic stud finders work on wood-frame walls; rare-earth magnet finders work for metal studs.
• Fish tape or fiberglass glow rods — used to push cable through finished wall cavities. Glow rods are rigid enough to navigate short horizontal runs. Fish tape is better for longer vertical drops.
• Long drill bit (ship's auger or flex-shaft bit) — a 3/4-inch or 1-inch ship's auger bit on an extension allows drilling through top and bottom plates from inside the wall cavity. A right-angle drill attachment is often needed in tight ceiling spaces.
• Low-voltage mounting brackets — installed in the drywall opening to hold the keystone wall plate cleanly without an electrical box.
• Punchdown tool (110-style) — used to seat conductors into keystone jacks and patch panels. A quality impact punchdown tool seats conductors more consistently than finger pressure alone.
• Cable tester — a basic wiremap tester confirms all 8 conductors are connected correctly. A more capable tester can measure length and detect split pairs.

Plan Before You Drill

Start with a simple map: where internet enters, where the router or switch will live, and where each wall jack should land. Prefer home-run cabling, where every room cable returns to one closet or network panel. It is easier to test, label, upgrade, and troubleshoot later.

Planning the Route: Attic, Basement, and Interior Walls

The easiest cable routes avoid finished surfaces entirely. The best approach depends on what your home provides:

• Attic drop — drill through the top plate into the wall cavity and drop cable down from above. Works well in single-story homes or for second-floor rooms. Confirm the wall cavity is open from top to bottom before committing.
• Basement rise — drill up through the bottom plate. Works for ground-floor rooms and any room directly above an unfinished basement. Watch for pipe chases that block the cavity.
• Interior wall runs — horizontal runs inside finished walls are harder. Use glow rods, a flexible drill bit, and cut small access holes at obstacles. Running behind baseboards is an option when fishing through drywall is impractical.

Avoiding Electrical Wires and Fire Blocking

Low-voltage cable must not share a hole or box with mains electrical wiring unless hardware is specifically rated for it. Keep Ethernet at least 2 inches away from electrical cables when running parallel, and cross electrical wires at 90 degrees to minimize inductive interference.

Fire blocking is horizontal wood blocking installed inside wall cavities, usually at mid-height in two-story walls, to slow fire spread. When your drill or fish tape stops unexpectedly, fire blocking is often the cause. You must drill through it — use a long bit and work carefully so you do not damage existing wiring or pipes on the other side. Some jurisdictions require you to restore fire-stopping material (such as fire-rated caulk or foam) around any new penetrations.

Terminating with Keystone Jacks (568-A vs 568-B)

Both T568-A and T568-B are valid wiring standards and both support Gigabit Ethernet equally well. The only rule is consistency: use the same standard on both ends of every cable. T568-B is the more common choice in North American residential installations. T568-A is used in some government and older commercial work and is also needed when making a crossover cable (one end A, one end B).

To terminate a keystone jack, strip about 1 inch of outer jacket, untwist each pair just enough to seat the conductors in the jack's color-coded slots, and punch them down one pair at a time. Do not untwist more than 0.5 inches of twist — excess untwisting degrades high-frequency performance and can cause a cable to fail at Cat6 speeds.

Basic Pull Sequence

1. Cut low-voltage mounting openings at the room and closet locations.
2. Inspect the path with a stud finder and, if needed, a small inspection hole.
3. Drill through top or bottom plates only when you know what is behind them.
4. Pull more cable than you need and leave a service loop at both ends.
5. Terminate to keystone jacks or a patch panel using the same wiring standard on both ends.
6. Test wire map first, then confirm negotiated link speed with a switch.

Testing the Run

Test every run before closing the wall. A basic wiremap tester checks that all 8 pins are connected correctly, no conductors are swapped, and there are no shorts. Common failures are split pairs (conductors from two different pairs swapped) and open conductors (a wire not fully seated in the jack). Both pass a simple continuity test with a tone probe but fail with a wiremap tester — which is why a real tester is necessary. After confirming the wiremap, plug both ends into a switch and confirm the port negotiates at the expected speed (1000 Mbps for Cat6, 10G for Cat6a on a 10G switch).

Hiring a Pro vs DIY

DIY in-wall Ethernet is reasonable in single-story wood-frame homes with accessible attic or basement space. The job becomes significantly harder — and worth hiring out — when the home has concrete or masonry walls, metal studs (common in newer construction), blown-in insulation blocking wall cavities, or fire codes requiring licensed low-voltage contractors. A professional low-voltage installer typically charges $100–200 per run including termination and testing, which is often competitive with the time cost of a difficult DIY pull.

Common Mistakes

• Using stranded patch cable inside walls — stranded cable is designed for short, frequently flexed patch runs, not permanent installation.
• Stapling too tightly or bending the cable sharply — Cat6 has a minimum bend radius of about 1 inch; crushing or kinking the cable degrades high-frequency performance.
• Running parallel to power cable for long distances — keep at least 2 inches of separation.
• Forgetting labels until all blue cables look identical — label both ends before you close the wall.
• Closing walls before testing each run — a failed run discovered after drywall is repaired requires reopening the wall.

Frequently Asked Questions

What cable should I run through walls?

Solid copper in-wall rated Cat6 is the practical default. Use Cat6a if you are intentionally building for longer 10GbE runs and can handle the thicker cable and tighter bend radius requirements.

Can Ethernet share a hole with electrical wiring?

No. Keep low-voltage Ethernet separated from mains wiring and use proper low-voltage brackets and plates. Sharing a box with mains wiring is a code violation in most jurisdictions.

Should I terminate in-wall Ethernet with RJ45 plugs?

Usually no. Terminate fixed cable to keystone jacks or a patch panel, then use patch cables for devices. Field-terminated RJ45 plugs on solid-conductor cable are harder to seat correctly and are a common failure point.