Aquariums, mirrors and bookshelves: the hidden Wi-Fi obstacles

You checked the walls. The thing blocking your signal may be a fish tank, a wardrobe door or the floor heating.

Published · 2 min read

In this guide
  1. Water
  2. Mirrors
  3. Metal you stopped noticing
  4. Dense furniture
  5. What's inside floors and walls
  6. How to catch one
  7. See the shadows on a map

When a room has poor Wi-Fi, people count the walls. Often the culprit is a piece of furniture, or something you can't see at all.

Water

Water absorbs Wi-Fi very effectively.

  • Aquariums. A large tank is a wall of water. Nintendo's own support page lists "near an aquarium" among the places not to put a console or router.
  • Hot water tanks and boilers, which add a metal shell to the water.
  • People. A body is mostly water. A room full of guests, or you sitting between your laptop and the router, makes a measurable difference.

Mirrors

A mirror is glass with a thin metallic layer behind it. That layer reflects radio. A full-height mirrored wardrobe is, for Wi-Fi, a metal wall: see why there's no Wi-Fi in the bathroom.

Metal you stopped noticing

  • Fridges, ovens, washing machines: see Wi-Fi in the kitchen.
  • Radiators, especially under a window where you'd like to put the router.
  • Metal shelving, filing cabinets, safes.
  • The TV, a large flat sheet of metal and electronics: see smart TV buffering on Wi-Fi.

Dense furniture

A bookcase packed with books is thicker and denser than the wall behind it. So is a full wardrobe. One of these between router and sofa costs as much as an extra wall.

What's inside floors and walls

  • Underfloor heating, with its pipes and often a foil layer, is one reason upstairs can be so much weaker: see Wi-Fi weak upstairs.
  • Foil-backed insulation in roofs and renovated walls: see Wi-Fi in the attic.
  • Reinforced concrete, with its steel mesh, and metal mesh behind old plaster.
  • Coated energy-saving glass, which reflects radio as well as heat: see Wi-Fi in new builds.

More on materials in what walls do to Wi-Fi.

How to catch one

Hidden obstacles have a signature: the connection is fine on one side of the object and poor directly behind it, in a "shadow" that follows the line from the router. Two quick checks:

  1. Move one metre sideways. If stepping out from behind the object fixes it, you've found the shadow.
  2. Move the router one metre. The shadow moves with it: see Wi-Fi drops in one spot only.

See the shadows on a map

Shadows are hard to guess and easy to see. Map the room with WiFi Heatmap, taking points on both sides of the fish tank, the mirrored wardrobe or the bookcase. A red patch that starts right behind an object and points away from the router tells you what to move.