The drywall is up. The paint looks perfect. But the Wi-Fi keeps dropping and your smart TV buffers constantly. If you’ve wondered why your ethernet is slow in your new house, the answer is usually hiding behind those freshly painted walls.

A simple, avoidable mistake made months earlier during the wiring phase is often to blame. These low voltage wiring errors aren’t always obvious during construction, but they show up the moment you move in. Here’s what goes wrong and how to prevent it.

The Most Expensive Wiring Mistakes at a Glance

Running Data Cables Too Close to Power Lines

Think of it like trying to have a quiet conversation next to a roaring subway train. Data cables running parallel to high-voltage electrical lines pick up electromagnetic interference that disrupts the signal.

What You’ll Notice

Unreliable Wi-Fi connections. Ethernet speeds that never reach their rated potential. Crackling in audio systems. Random data errors that seem impossible to diagnose.

How to Prevent It

Low-voltage data cables should maintain at least 12 inches of separation from electrical cables when running parallel. If they must cross, they should intersect at a 90-degree angle.

In tight Manhattan apartments and Brooklyn brownstone renovations, every trade competes for limited space inside walls and ceilings. A coordinated new construction cabling plan before anyone starts pulling wire makes all the difference.

Cheap Cabling That Fails When You Need It Most

Not all ethernet cable performs the same. Copper Clad Aluminum cables cost less than solid copper, but they’re brittle, less conductive, and don’t comply with TIA industry standards.

What You’ll Notice

Connections that fail over time. Network ports that suddenly stop working. An inability to deliver Power over Ethernet to security cameras or Wi-Fi access points.

How to Prevent It

Always specify and verify that your installer uses 100% solid copper Category 6A or better cabling from a reputable manufacturer.

Pro-Tip: Ask to see the box the cable came in. It should be clearly marked as solid copper and rated for the category you specified. If the installer can’t show you the packaging, that’s worth questioning.

Not Installing Enough Network Drops

A minimalist approach to wiring rarely pays off. Homeowners and builders sometimes try to save a few hundred dollars by installing only one or two ethernet ports in the entire home. This is one of the most common pre-wire mistakes in new construction projects.

What You’ll Notice

A home office that depends entirely on spotty Wi-Fi. A media center buried under switches and tangled cables. No wired option for the bedroom smart TV.

How to Prevent It

Plan for a minimum of two data drops in every key room. Living room, home office, bedrooms. Running an extra cable during construction costs almost nothing compared to opening finished walls later.

A cabling subcontractor involved during the rough-in phase can help you plan for both current needs and future expansion.

Bending Cables Too Sharply or Cinching Bundles Too Tight

Data cables aren’t as forgiving as standard electrical wire. Exceeding the bend radius or using plastic zip ties to cinch bundles too tightly damages the internal copper pairs and degrades performance over time.

What You’ll Notice

A network port that tests fine during the walkthrough but fails under heavy load. A gigabit connection that only registers at 100Mbps. Intermittent dropouts during video calls. These are classic network cable installation mistakes.

How to Prevent It

Installers should follow the manufacturer’s specified bend radius for each cable type. Loose-fitting Velcro straps work better than plastic zip ties for bundling cables.

Pro-Tip: The rule of thumb for bend radius is no tighter than the diameter of a coffee mug. If it looks kinked, it probably is.

Forgetting to Document Before the Drywall Goes Up

This isn’t a technical mistake. It’s a process mistake with major consequences. Once the walls close, you lose all visibility into where cables actually run.

What You’ll Notice

You hang a picture and drive a nail through a critical data line. You want to add a new outlet and have no idea what’s already in the wall. A future technician spends hours troubleshooting because there’s no documentation.

How to Prevent It

During the pre-wire walkthrough, take detailed photos and videos of every wall and ceiling cavity before insulation and drywall go up. Label these images by room and store them digitally.

This documentation becomes invaluable for future service calls. It’s also a selling point when your apartment hits the market, giving the next owner a clear map for their technicians.

Using Cable Not Rated for the Installation Environment

This is different from cable quality. Even solid copper Cat6A will fail if it’s not rated for where you install it. Indoor-rated cable used outdoors degrades from UV exposure. Standard cable in air handling spaces violates fire codes. Unshielded cable near motors or fluorescent lighting picks up interference.

What You’ll Notice

Insulation that cracks or becomes brittle within a year. Failed inspections that delay your certificate of occupancy. Intermittent signal problems that only appear under certain conditions.

How to Prevent It

Match the cable rating to the installation environment. Use plenum-rated cable in air handling spaces and drop ceilings. Choose UV-resistant, outdoor-rated cable for any exterior runs. Install shielded cable near sources of electrical noise.

Ignoring Voltage Drop on Long Cable Runs

Voltage drop happens when electrical resistance in the cable reduces the power available at the far end. This matters most for low-voltage lighting, powered devices, and PoE equipment. A 3-volt drop that’s negligible in a 120V circuit can completely disable a 12V system.

What You’ll Notice

LED landscape lights that dim noticeably at the far end of a run. Security cameras that randomly reboot or won’t power on. Access control panels that behave erratically.

How to Prevent It

Calculate voltage drop for any cable run longer than 25 feet. Keep total drop under 5% for general use and under 3% for sensitive equipment. For longer runs, use a larger gauge wire or add a power source closer to the load.

Common Questions Answered

Which mistake costs the most to fix after construction?

Not installing enough network drops. Opening finished walls to run new cables costs significantly more than adding extra runs during the rough-in phase. The cable itself is inexpensive compared to the labor of cutting, patching, and repainting drywall.

How can I tell if my installer used quality cable?

Ask to see the original packaging. Quality cable is clearly marked with the manufacturer name, cable category, and “solid copper” designation. Avoid any cable marked CCA or cable without clear labeling.

Do I need permits for low-voltage wiring in NYC?

Low-voltage work typically doesn’t require the same permits as high-voltage electrical, but it depends on the scope of your project. Work involving fire alarm systems, building-wide infrastructure, or modifications to common areas in co-ops and condos often requires permits and inspections.

How far should data cables be from electrical wires?

Maintain at least 12 inches of separation when running parallel to electrical cables. If data and power cables must cross, they should do so at a 90-degree angle to minimize electromagnetic interference.

Planning Your Low-Voltage Wiring Early Prevents Expensive Fixes

A successful smart home starts with thoughtful wiring. These mistakes are easy to make but equally easy to avoid with some planning upfront.

The most reliable way to sidestep these issues is working with experienced installers during the new construction cabling phase. A solid structured cabling foundation is one of the smartest investments in any home’s technological future.