Slow WiFi despite fibre? Here's why — and how to fix it

Fibre stops at the box: the rest is radio

The fibre speed your provider advertises is measured at the socket, over a cable. The moment data goes wireless it becomes a radio wave subject to physics: distance, walls, interference. A home can have perfect fibre and terrible WiFi — the two simply have nothing to do with each other. That's why switching providers almost never fixes a coverage problem.

Cause #1: the box is in the wrong place

The box sits wherever the provider's technician found a socket: the hallway, a cupboard, the garage, behind the TV. Every metre and every wall costs you speed. At 10 metres and two walls, losing 80–90% of your bandwidth is common. In Nice's old stone apartment buildings or the reinforced-concrete villas in the hills, a single wall can kill the signal.

The simple test: run a speed test (Speedtest, nPerf) right next to the box, then in the problem room. If the ratio is 10 to 1, you have a distribution problem, not a subscription problem.

Cause #2: WiFi channels saturated by the neighbours

In apartment buildings — very common along the coast from Nice to Menton — dozens of boxes broadcast on the same channels. WiFi is polite: everyone waits their turn to talk. The more neighbouring networks, the more your speed collapses, especially in the evening. The 2.4 GHz band carries far but is the most congested; 5 GHz is faster but struggles through walls. Professional equipment picks channels intelligently and steers each device to the right band — a lone provider box does this poorly.

Cause #3: the cheap extender that "shows full bars"

The classic reflex: buy a €30 extender. The result: full bars, but your speed is cut in half (the extender listens and repeats on the same radio) and your phone stays stubbornly attached to the far-away antenna. Bars measure signal, not usable speed. We wrote a full guide on choosing between extenders, powerline and mesh — spoiler: above 80 m², the only lasting fix is a real network (quality mesh or cabled access points).

Causes #4 and #5: in-wall cabling and box settings

Two lesser-known culprits: homes wired with ethernet sockets… that were never actually connected to the patch panel (very common in 2000s builds), and counter-productive box settings (a "smart WiFi" that forces the wrong band, a channel pinned to a crowded one, old firmware). A serious diagnosis checks both: sometimes simply connecting the panel and activating the existing ethernet sockets transforms the house without running a single new cable.

What actually works, by property size

What we install, after measuring on site:

• Apartment up to ~80 m²: box repositioned + clean settings, sometimes one extra access point. Often the shortest quote.
• House or duplex 80–150 m²: a high-end mesh network with a dedicated link between units, or cabled access points if conduits exist.
• Villa, thick walls, annexes, pool area: professional Ubiquiti UniFi access points on ethernet — the hotel-grade solution, no subscription, guaranteed room by room.

Whatever you do, demand one thing from your installer: speed measured in every room at the end of the job, with a written report. That's the only proof that matters.