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How Much & Which Building Materials Block Cellular & WiFi Signals?

Dec 21, 2021

How Much & Which Building Materials Block Cellular & WiFi Signals?

Have you ever wondered how much do various kinds of building materials block cell phone and Wi-Fi signals? Well, here's your chance to find out! If you have reception problem with your cell phone, you may find that you're a bit frustrated with trying to determine the cause of your weak signal. Your phone works in some spots outside of your home, but inside your abode, there is little to no signal at all. Obviously, there's something in the house which is stopping the reception, but what is it?

While Mother Nature does block cell signal from -5 to -25 dB where rain attenuates signal anywhere from -1dB to -5dB and foliage attenuates it anywhere from -1dB to -25dB, the odds are that it is your home building materials that blocks most of your signals. They are the number one cause of cell phone reception disruption. Knowing which materials can deflect your cell phone reception may help you to find solutions to increase or gain your signal using a cell phone signal booster or similar device. Or even help you reduce reception if you're concerned about radiation affecting your health. Either way, listed below are the top building materials that stop wifi and cell phone signals in its tracks.

Please note that while we mostly mention mobile signal strength attenuation figures below, wifi signal strength is similarly attenuated. The 802.11 standard provides several distinct radio frequency ranges for use in Wi-FI communications: 900 MHz 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz and 60 GHz bands. Each range is divided into a multitude of channels. Therefore, we won't go into too many details to prevent getting sidetracked or distracted with all mobile and wifi frequencies and channels. Nevertheless, you will get a rough idea from the fully researched list below roughly how much of the signals will get attenuated by which products/ materials.

Clear Glass.

There's a misconception that clear glass fixtures, such as windows, are the best place to gain access to a signal. While the clear area is ideal for letting in light, they can bounce a signal around or reflect the signal away from the house. This is especially true for windows which are double insulated. There're triple pane windows in newer homes with reflect signals even more. The most deflecting ones are the latest low emission (Low-E) windows that keep the elements out to keep you warm or cool inside depending upon the weather outside. But if you're looking to improve cellular reception by standing next to a window, open that window for most impact. Blockage on windows can reach -4db.

Sheetrock and insulation.

Sheetrock is one of the lower blocking agents for a cell phone signal. However, it can cause your signal to be blocked completely if it is already weak. Keep in mind that 3G, 4G, 5G signals are generally the same as a radio signal and so you can see fluctuations in your signal of -2db. Closed rooms, meaning those which are not a part of an open floor plan, are more susceptible to cell phone signal disruption than sheet rocked rooms which are part of an open layout.

Although porous, fiberglass insulation in walls and attic can disrupt cell phone signals slightly, if it is thick enough. Foil-faced design of some insulation products helps keep out unwanted elements. However, foil facing used on insulation products like foam board or fiberglass batts can block radio frequency signals. Additionally, the interior walls made with denser materials can cut the reception down another -2db. In this manner, sheetrock and insulation has the potential to cut your cell phone reception before it even enters your home.

Plywood, Solid wood, Trees around the house.

Plywood which makes the majority of the structure and framework for many residential homes, reduces 3 and 4G networks up to -6db. Reduction is even higher at -9dB on 5G network. This number fluctuates a bit as there're different thicknesses of plywood, and different ways in which the plywood is compressed. Additionally, the cell phone reception loss can be increased should the plywood get damp/wet with numbers as low as -20db. But if the plywood on your house is wet, you have bigger issues to worry about(!)

Solid wood, such as that used in the flooring of the house builds upon the blocked signal of the plywood. While the finishing on the doors, floors, decking, etc. may be nice for that natural look, they are cell phone signal blockers. All wood slows down a signal. The thicker the wood, the more it will disrupt cell phone signal strength. Softer woods, such as pine, may not decrease the strength much, but you could still see a loss of -5 to -12db. Aside from indoor plants, trees outside including Pine trees that have branches with dense growth of leaves block signal to this or greater extent. The degree of blockage depends on the age or how old the trees are, and the size, or how large the trees are. Older and larger a tree surrounding a house, the more dead zones you can expect in the house.


Though incredibly sturdy against the elements, brick is one of the top materials for blocking a signal. First you have the thickness of the brick which slows the signal down. Secondly, you have mortar between the bricks which does not allow a signal. Additionally, brick generally has supplementary materials on the interior so that electronics, sheetrock, shelves, etc. can be added. The mere thickness of the wall combined with the density of this building material can block up to a whopping -28db scale.


When it comes to building materials, Metal is the top cell phone signal disrupter. Metal roofs as well as metal studs and interior metal will slow down the signal. While metal looks nice on a building, is durable against the elements, and can help with routing electricity and such away from the walls underneath, it can also route the signal away from the house. Most houses which have metal roofs will find that even if they live in an area where exterior signals are strong, interior signal strength will be weak if not non-existent. Ratings can drop as low as -32 to -50db, essentially making your home a dead zone. Along with 3G and 4G LTE, metal roofs deflect 5G signals the most because 5G uses higher frequencies that can penetrate metal the least.

Faraday Products.

If you're in a situation where you need to purposely block signals to prevent oscillation because your cell phone signal booster exterior and interior antennas are too close, then we carry high tech Faraday series maximum signal blocking materials to get the job done.

List of Materials and How Much They Block Cellular Signal:

Building Material 800 MHz Cellular Band 1900 MHz PCS Band
1/2" Drywall 2.03 dB 2.43 dB
Venetian Plaster 7.91 dB 16.22 dB
6" Concrete Wall 10.11 dB 19.41 dB
Glass Window 4.35 dB 4.38 dB
1/4" Fiberglass 1.62 dB 1.90 dB
Low Emission Glass Window 33.8 dB 33.8 dB
Brick 7.57 dB 14.66 dB
Solid Wooden Door 6.11 dB 12.33 dB
Hollow Wood Door 5.39 dB 10.11 dB
1/2" OSB Plywood 3.27 dB 4.91 dB
1/2" Solid Pine 2.01 dB 5.05 dB
1/2" Solid Oak 4.68 dB 6.11 dB

Why should I care about the db and how can I increase my signal strength?

The decibels (dB) detected by your phone is how the signal strength is measured most accurately. This is true whether your phone is using 2G, 3G, 4G LTE, or 5G. A good signal strength metric is RSSI - Received Signal Strength Indicator. RSSI is a negative value, and the closer to 0, the stronger the signal. In other words, the closer to -50db you are, the better the signal because it typically ranges from -50 (strongest) to -120 (weakest). Keep in mind that a -120db is a deadzone while -50 is full bars. This is not to say that metal will put your phone at -120db though (dead zone). It may put it at -100db or more. The closer to -50 dB, the better the cell reception. Find out how to check signal strength in decibels on your phone or see the full scale chart showing the correlation of Received Signal Strength Indication (RSSI) in dBm or Decibel-Milliwatts versus corresponding Signal Strength in laymans terms below:

RSSI in Decibels vs Signal Strength

To increase your signal in your home, use a residential cell phone signal booster. Follow the steps in other articles on finding the best spot for your cell phone booster. Should you have questions about which booster is best for your home, business, or commercial space, try our phone booster selection tool or please call us - we would be happy to help you find the right phone booster.

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  • Metal roofs are generally not a problem in areas of otherwise good coverage. In fact, when I installed my new metal roof and then added thermal reflective barrier under the rafters I actually increased my reception for both wifi and cell coverage.

    if things work out for the best, these reflective surfaces can create an excellent reflective surface to HELP with your reception. Do not think that just because a roof is metal that you lose reception and coverage. Just the opposite might be true!

    jea3 on
  • Very good info. Was considering a metal roof on my manufactured home but thank the “cell gods” I didn’t do it. From my experience, you’re way better off with GSM for penetrating your house than CDMA. Nothing but grief with Verizon (on Straight Talk) in my house. Had to put my phone on a window sill facing the Hwy to stream anything. Switched to ATT sim (also Straight Talk) and poof! I can go anywhere in my house, in a closed closet or the bottom of the toilet and I can stream video without a glitch. The ATT and Verizon towers are in nearly all the same locations up and down the Hwy near my house (in the sticks in Northern Arizona – just South of the Grand Canyon) but the ATT GSM signals are tops in my house. Long live GSM!

    Jim Kirk on
  • Live in Mobile home with an aluminum roof with a tin roof over that with a 2 foot clearence. Will your product help with a straight talk phone. I get NO SERVICE inside my house. Leave out in the boonies. HELP!

    MCI on
  • Nothing is ever as easy as it looks. I appreciate the effort made to set these videos and instructions up but I am skeptical that things can be put into place so easily. Maybe I’m wrong. I just don’t want to buy a vehicle cell booster and get a migraine trying to put it in.

    Alfonso M. on
  • Interesting comments. I find it very interesting that since changing to T Mobile we have lots of dropped calls, garbled voices and texts that don’t send. I’m not sure why my iPhone 12 doesn’t work better, but it is a poor substitute for my old 7 iPhone. No problems there. Anyway, I called T Mobile and they said because it is the house, it isn’t their issue. I call BS… as the calls made on Verizon got through, very few dropped calls or text issues. Putting the problem on a building is making it a scapegoat. For what is paid to them for service every house should be able to capture a signal. Now answer me this… if people can use wifi for their phones, why do they need a phone company at all? Just use the wi-fi. Well, I hope you can tell that I’m frustrated with the technology, the companies and the expense for a service that isn’t… why should we pay if we can’t get the signal? Isn’t the contract with any cell phone for them to provide service to your phone and on to another phone and the other phone back to you? If that doesn’t work I think paying is usery… as we are paying for service we don’t get. Oh, BTW, T Mobile sent us a signal booster to help with our problem… it is a wi-fi booster… ironic since Nathan (our tech rep) said we need to turn off all wi-fi on our phones and just use their service. Why then did the company send us a wi-fi booster??? With all this bitchin’ I’m not unhappy with what I’ve read. this is a great discussion and thank you one and all for writing.

    KaCe on
  • I never thought the glass would be what causes problems. My mind is blown. No way. jj

    jada jay on
  • I had a steel roof installed on my home in late 2017. My cell phone reception was very sketchy after that.

    Then I got a new cell phone, and most of my reception problems went away.

    But Verizon is finishing up a 5G tower 200 feet from my back door, and that conceerns me greatly.

    Also wondering if that tower may affect my property value in the future.

    Richard Canary on
  • How far do Wi-Fi signals travel outside house your home typically an uninsulated home

    Jim on
  • Question. Carbon. Particularly paper. very thin caliper paper. Almost as “thick” as tracing paper. If something is being tracked by a powerfully strong signal locater, for instance a GPS sattelite in orbit. Would a thick sheet, or a number of
    thick carbon “wrapping” sheets be able to make the wrapped item undetectable?

    Cameron Knights on
  • My house has literally become a deadzone. I go outside and have decent to real good signal pretty much all the time but as soon as I come inside I lose any and all signal I have. I’ve tested my signal a lot lately mainly to see if the strength of the signal is by chance getting better but each time it’s the same. It’s consistently been between -115db and -130db with the last test I did being -126db. I have a metal roof but should it be causing complete loss of signal like that?

    Tyler Slaten on
  • Is there a test method for testing the signal loss of 5G through materials? Is there a reference for the above data that we can access?

    Eileen G on
  • I must confess I was very interested and impressed with the thoroughness if your reporting; however, what I needed to convince me were links to the studies on which the reported facts were based. Are they available anywhere?

    Michael Koszyca on
  • I’m glad there is research being done on what materials can block a wifi signal because this blog opened my eyes to what materials can block wifi signals. Unbeknownst to me, there are many materials that do so. That explains why there are so many iffy areas in my home where I get dropped calls or crummy reception. If someone wanted to figure out how to block a wifi signal from the router, they could come to my home. My back room has the worst wireless signal and I live in a smaller house. Thanks to this blog, I know how to get around these problems (besides buying a new home).

    Kyle Hogan on
  • 5G is a completely different animal. What on God’s Earth will block that nefarious signal ?

    nlightn on
  • I look at this list of materials and I start to shudder. What can block a wifi signal? Pretty much everything that’s found in your home and office. Who would have imagined glass could block a wifi signal? Apparently, there’s a lot of research into what can block a wifi signal, as seen with the evidence here. A cell phone booster might be the way to go in my home, because I’m always having problems with signals. Glass? Oh man, it’s worse than I thought.

    Andrew Reilly on
  • It looks like there aren’t many materials that help with signals. This pretty much measures up to what I’ve seen wherever I go. I’ve been in condos, townhouses, beachhouses, and homes, and there are always problems with cell coverage. I gotta say it is cool to know how to boost cell phone signal strength using these cell phone signal booster doo-dads.

    C.C. Tompkins on
  • I love this site. I learn so much about cell phone technology by browsing the various articles. I always thought a window was a surefire way to get a good signal while inside. Apparently not. It’s amazing how poor cell phone reception can be inside your home, even when you have a decent cell phone.

    Michael Rickard on

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