11 Major Building Materials That Kill Your Cell Phone Reception

11 Major Building Materials That Kill Your Cell Phone Reception

Written by Wilson Amplifiers
28th Jan 2020

What Can Interfere With Cell Signal

It's no secret.

Building structure and material is generally the leading cause of poor cell phone signal in America.

Even if you live in the boonies where cell tower distance is a big problem, having a metal roof or brick wall is basically the final death nail of any hope for carrier service to work inside your home.

3G & 4G LTE signals are radio frequency waves. And like all radio waves (cellular, wifi, AM/FM, satellite, etc.), just a bit of interference or obstruction and you've got reliability as durable as a 3-year old's attention span.

Today we look at the top building materials that utterly stop RF signals on their tracks.

But first a quick explainer.

See complete cell signal booster kits for your situation:


How cell phone signal strength is really measured

The number of bars on your phone is really subjective.

How subjective?

It's not really tied to any standard. It's up to your carriers to decide how much is 1, 2, 3, 4 or full bars on their service.

So what's 1 bar on Verizon might be 2 on AT&T, 3 on Sprint or full bars on T-Mobile despite receiving the exact same signal and performing at the exact same speeds.

But luckily, there's a way to find out your true signal strength. It's called decibel (dB) reading. This is measured in decibel-milliwatts, or dBm.

Cell phone signal operates with a certain frequency:

-50 dBm to -120 dBm.

-50 dBm is full bars. -120 dBm is basically a dead zone. The closer you are to - 50 dBm, the better your signal.

So what does this have to with building material?

Well, building materials basically subtract dB from your signal when trying to enter your home. The more it subtracts, the closer you get to -120 dBm which is a dead zone.

Let's look at which materials obstruct 3G & 4G LTE signals.

The Top 11 Building Materials That KO Your Cell Phone Signal

11. Mother Nature (-3 to -20 dB)

11. Mother Nature (-3 to -20 dB)

Ok, so it's not technically building material, but nevertheless, a good starting point. People often wonder: do trees block cell signal? The answer: a resounding yes.

Trees, mountains, hills, and even weather can affect your cell phone signal. Just how much though?

Rain: -3 to -5 dB

Foliage: -7 to -20 dB

Foliage is a very big problem since they're very capable of blocking cell signal, especially pine cones. Most homes and offices find their signal to be working much better in the autumn.

The reason?

Falling leaves means less aerial obstructions. Yup.

10. Drywall /Sheetrock (-2 dB)

10. Drywall /Sheetrock (-2 dB)

Your interior walls and ceilings are most likely made from drywall, and they are the first interior line of defense preventing signal from getting into the room.

9. Fiberglass Insulation: Does Carbon Fiber Block Cell Phone Signal (-2 dB)

9. Fiberglass Insulation: Does Carbon Fiber Block Cell Phone Signal (-2 dB)

Fiberglass insulation either in the walls or up in the attic also block cell signals. When tag-teaming with drywall, it's already at -4 dB which means signal outside is already cut by 50% by the time it enters your home.

8. Clear Glass (-4 dB)

8. Clear Glass (-4 dB)

While windows are great for letting in the light, view, and heat, they're also capable to reflecting and refracting cellular signal up to -4 dB.

7. Plywood (-4 to -6 dB)

7. Plywood (-4 to -6 dB)

Plywood is another sheet material that reduces 3G & 4G LTE signal. And if plywood gets wet and is not water resistance, it will act as a sponge capable of weakening signal up to -20 dB. Ouch.

6. Solid wood (-5 to -12 dB)

6. Solid wood (-5 to -12 dB)

That nice wooden door or furnishing? A cell signal killer. Any type of wood from beech, ash, oak, mahogany, maple, etc. is very capable of absorbing and blocking signals. The thicker the wood the worse the signal.

5. Plaster (-8 to -16 dB)

5. Plaster (-8 to -16 dB)

Plaster is building material made from gypsum, lime or cement used for protective coating on walls and ceilings. Who would have though such a thin layer of paste could do that much damage?

4. Brick (-8 to -28 dB)

4. Brick (-8 to -28 dB)

Bricks made from clay, shale, or cement is great building material for aesthetics and design. But while preventing the big bad wolf from blowing it down, it also shuts out cellular signals.

3. Concrete & cement: 6 inches (-10 to -20 dB)

3. Concrete & cement: 6 inches (-10 to -20 dB)

No surprise here. Most modern buildings are made from concrete. Many architects depend on the industrial strength of concrete & cement to create robust structures, so many urban areas have challenges to get working signal indoors.

2. Tinted & Low-E Glass (-24 to -40 dB)

2. Tinted & Low-E Glass (-24 to -40 dB)

Newer building use energy-efficient material like low-e glass to keep heat out. Unfortunately, they're also good at reflecting cellular signal back.

1. Metal: What Metal Blocks Cell Signal (-32 to -50 dB)

1. Metal: What Metal Blocks Cell Signal (-32 to -50 dB)

People often ask: do metal roofs block cell phone reception? Sadly, yes, a great deal.

Aluminum, aluminum foil, lead, brass, copper, steel, iron, etc. Metal is the #1 cellular blocking material across all buildings in America. People with metal roofs find it difficult to get reception. Even having metal inside the home creates distortion for RF signals.

We've written a guide to getting better cell signal inside a metal building for those who suffer from this problem.

Building Material that Blocks Cell Signal Infographic

To sum this article up, we've created this handy infographic to illustrate our main points. Let this be a simple visual summary of all we've discussed!

materials that block signal infographic


Literally almost anything under the sun can affect your cellular signal. When looking at the whole picture, a typical house with drywall, plaster, glass, and wood can lose up to -30 dB or more.

In "bar speak," that's about a loss of 2-4 bars, the difference between having working service outside and having none inside.

What other building material is affecting your home or office? Let us know in the comments below.

Building Material dB Loss
Foliage -3 to -20 
Drywall -2 
Fiberglass Insulation -2 
Clear Glass -4 
Plywood -4 to -6
Solid wood -5 to -12
Plaster -8 to -16
Brick -8 to -28
Concrete & cement (6 inches) -10 to -20
Tinted & Low-E Glass -24 to -40
Metal -32 to -50

How to Boost Cell Signal

Wilson Amplifiers is the leading provider of cell phone signal boosters. Cell phone boosters amplify 3G & 4G LTE for any phone with any carrier for home, office, or vehicle.

We seriously hate dropped calls and poor coverage, so it's our goal in life to stomp on spotty signal like the little roaches they are:

  • Free consultation (ask us anything) with our US-based customer support (sales@wilsonamplifiers.com) or call us at 1-800-568-2723.
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