Why is my mobile signal bad at home? Causes and fixes

Poor reception at home is rarely a mystery once you know where the masts are and what stands in the way. Below are the common causes, roughly from most to least frequent, with a fix for each.

1. The building is blocking the signal

This is the most common cause. Mobile signals lose strength every time they pass through a wall, a floor or a window, and some materials are much worse than others:

• Thick stone, concrete and brick, common in older French houses and apartment blocks.
• Metal: steel frames, metal roofs, shutters, cladding and foil-backed insulation.
• Energy-efficient glazing, which often has a thin metallic coating. A house renovated to high insulation standards can lose most of its indoor mobile signal.

A simple test: if you have good signal in the garden or on the balcony but poor signal inside, the building is the problem. Fixes are Wi-Fi calling (see below), a 4G/5G router placed by a window facing the mast, or an outdoor antenna.

2. Your carrier's mast is far away or hidden

Masts are shared between carriers only partly. Your neighbour on another network can have excellent signal from a mast your carrier doesn't use. Look up your address on the map and check the nearest mast for your carrier and its direction. If it is several kilometres away, or behind a hill or a ridge, the signal will be weak whatever your phone does.

Each town page lists the nearest mast per carrier, which makes it easy to see whether another network would be better placed for you. Our guide on choosing a carrier by coverage explains how to compare them.

3. You are on a high-frequency band

Low bands (700 and 800 MHz) travel further and go through walls better; high bands (1800, 2100, 2600 MHz and 3.5 GHz) are faster but fade quickly indoors. Phones often hold on to a high band until it is almost unusable. That's why a phone can show full bars outside and drop to one bar a few metres inside. There is no setting for this on most phones, but routers often allow band selection.

4. The cell is busy

A cell has a fixed capacity shared by everyone connected to it. At busy times (evenings, events, train stations) your signal can look strong while data is slow. The tell-tale sign is good signal bars but slow speeds that recover late at night.

5. The phone itself

• Older phones may not support all the bands your carrier uses, especially 700 MHz.
• A thick or metal phone case can reduce reception.
• Restarting the phone or toggling airplane mode forces it to look for the best cell again.

6. A temporary fault or works

If reception suddenly gets worse in an area that used to be fine, a nearby site may be down for maintenance or upgrade. Carriers publish network status pages, and switching to another site can make reception worse for a few days.

What helps, by situation

Wi-Fi calling

All four French carriers support calls and texts over Wi-Fi (often called VoWiFi) on compatible phones. If you have a decent internet connection at home, turning it on in the phone settings is the cheapest fix for indoor call problems. Calls hand over to the mobile network when you leave.

Reporting a coverage problem

In France, you can report persistent coverage problems to your carrier, and also through Arcep's "J'alerte l'Arcep" platform. Arcep is the telecoms regulator: it does not handle individual complaints, but the reports help it monitor where networks fall short.