How much do walls and floors block Wi-Fi?

On 5 GHz, a brick wall takes about 10 dB off the signal, a concrete wall 15 dB, drywall 4 dB and the concrete slab between floors 18 dB. Metal, mirrors and the fridge are the worst: 20 dB.

Every 10 dB lost leaves one tenth of the power. That is why a single concrete wall divides the distance at which signal stays good by 4, and two brick walls take the range from 51 m down to 8.1 m.

Higher bands lose more: the same brick wall takes 6 dB at 2.4 GHz and 12 dB at 6 GHz.

How much does each material lose on each band?

Average values the planner uses, per wall crossed:

Material2.4 GHz5 GHz6 GHz
Brick or plastered ceramic block6 dB10 dB12 dB
Concrete, pillar or structural wall10 dB15 dB18 dB
Slab between floors13 dB18 dB21 dB
Drywall or plaster3 dB4 dB5 dB
Wooden door3 dB5 dB6 dB
Plain glass or window2 dB4 dB5 dB
Metal, mirror, fridge15 dB20 dB22 dB

Real loss changes with thickness, moisture and the steel inside the wall. A thick brick wall, or one with plaster that is still damp, can lose much more than the average; a thin partition, less.

What is a decibel, in practice?

The decibel (dB) compares two power levels on a multiplying scale, not an adding one. The numbers that matter:

  • 3 dB: half the power.
  • 10 dB: one tenth.
  • 20 dB: one hundredth.

Losses in dB add up: two brick walls on 5 GHz take 10 + 10 dB, and every 10 dB of that sum divides the power by ten. In the model, going through one brick wall on 5 GHz costs as much as multiplying the distance by 2.5.

Why do 5 and 6 GHz lose more through walls?

The higher the frequency, the more the wave is absorbed by the wall materials. In the model, good signal through one brick wall reaches about 43 m on 2.4 GHz, 20 m on 5 GHz and 12 m on 6 GHz. On the other hand, the higher bands are much faster and less crowded, which is why they are worth it near the router.

How much does the floor between stories block?

A concrete floor slab takes 13 dB at 2.4 GHz, 18 dB at 5 GHz and 21 dB at 6 GHz, almost as much as a concrete wall. The planner adds one slab per floor crossed and counts the 3 m between floors in the distance.

With the router downstairs, good 5 GHz signal reaches about 9.7 m upstairs in a straight line, before counting the walls up there. In homes with concrete floors, one node per floor is almost always worth it.

Do doors, windows and mirrors make a difference?

  • Wooden door: 5 dB on 5 GHz when closed; nothing when open.
  • Plain glass: 4 dB. Low-E or reflective glass has a metal coating and blocks much more.
  • Mirror: its backing is metal, and the model treats it as metal: 20 dB.
  • Aluminum sliding door, garage door and metal shower enclosure: metal too.

How do I tell what my wall is made of?

Knock on it: a hollow sound means drywall or a light partition. Columns and beams are concrete, and in many buildings the inner walls are load-bearing masonry that cannot be taken down; in the planner, treat both as concrete. Tiled kitchen and bathroom walls follow the wall behind the tiles. When torn between two materials, pick the heavier one: the result stays on the safe side.

The numbers in this guide come from the model the planner uses (distance loss with exponent 2.5 plus the loss of each wall) and have a typical error of ±8 dB. Use them to compare options, then confirm with a measurement once everything is set up.

Frequently asked questions

Does a thicker wall block more?

Yes. The values in the table are for walls of usual thickness in homes. The planner uses one value per material, not per thickness, so a very thick wall can be drawn as concrete to get closer to reality.

Do tiles or paint block Wi-Fi?

Ordinary paint changes almost nothing, and tiles add little. What matters is the wall behind them and any metal: plaster mesh, foil-backed insulation, pipes or a steel cabinet against the wall.

Can Wi-Fi go through a concrete wall?

It can, but it loses a lot: 15 dB on 5 GHz. In the model, good signal reaches about 13 m past one concrete wall on 5 GHz and 30 m on 2.4 GHz.