We have all experienced lousy reception. Either an important call is dropped, or an online meeting is interrupted. That’s a reality we have to deal with sometimes, but we don’t always realize the culprits behind this nuisance and the possible ways of fixing it. The reasons for poor signal can be very versatile. 

So if you have ever asked yourself, “what could be blocking my wifi signal?” read on to find out. If you are ready to do some exploring, let’s dig deeper into the problem and list the top materials that block cell phone signal, as well as wifi signal, starting from the most harmless and moving on to the ‘highly dangerous’ ones. 

Before we get to the main list, here’s a table to save your time in case you are looking for a quick answer. Note that the level of blocking can change depending on the bandwidth of the signal.

1. Natural obstacles

Yes, we love nature, and although this is not really a category of building materials, it was bound to appear on the list, wouldn’t you agree? Mountains, hills, forests, and even thick trees in the yard can create an obstruction, blocking cell phone signal. While we don’t encourage you to chop down all the trees between yourself and the cell tower, there are things you can potentially do. For starters, you can try a dead zone map. If you are planning on a trip, google the signal dead zones in the area to be aware and prepared. And, if you are planning to move to a spot that gets a bad signal, you can always use a signal booster to make your life easier and ensure a flawless connection. 

2. Sheetrock/ Drywall 

Another example of what can interfere with cell phone signal is sheetrock or drywall, used to cover the ceilings and construct interior walls. Now drywall is no threat when you have a strong outside signal, but when it’s weak as it is, drywall can make matters worse.  A ½’ thick sheetrock can lower the reception by -2 dB, which is significant enough to feel the difference. 

3. Ordinary clear Glass 

This one is surprising, isn’t it? It doesn’t seem to answer the question of what materials block cell phone signals. And yet it can lower your reception by -4 dB, due to its reflective qualities. A weak signal can just bounce right off, leaving you with dropped calls. As we mentioned above, this mostly happens in remote areas, where your outside signal is already pretty weak. In busy cities, usually, glass is not what blocks wifi signals. 

4. Fiberglass Insulation

As well as the previous entry on the list, the fiberglass by itself is not a big deal for the signal to sidestep. But pair it with sheetrock and bad outside reception, the result is no bueno. -4 dB, to be more precise. The insulation can be what blocks wifi signals and cell signals too, but don’t forget that it keeps you warm in winter and keeps the sound from traveling freely through the drywall, so it has many benefits.

5. Solid wood

Anything from flooring and decking to doors can slow down a signal. It is once again blocking cell phone signal and not doing much to stop the wifi. But it can absolutely lower cell reception by -5-10 dB. Thick doors might not be a good option when you have a weak signal coming in. On the other hand, pine is softer than most wood so that it won’t affect the signal much. 

6. Plywood

It is a vastly used material in construction. It makes up the main structure and framework in most residential homes. Plywood can significantly lower your dB-s anywhere from -4dB to even -20dB, depending on thickness, compression method, and dampness. Surprisingly enough, damp plywood does lots more damage in this case than the dry one. Once again, when it comes to the question of what materials can block a wifi signal, plywood is not the answer you are looking for. It will affect 3G, 4G, and 5G signals, but not wifi. 

7. Plaster

Plaster is a building material used to cover the walls and the ceilings to make it smoother in texture and hide any kind of imperfection of the surface or correct a curve in the wall. This is a very popular material when working with brick walls as opposed to plywood and insulation, so this mostly occurs in older buildings and houses. When it comes to blocking cell phone signal, plaster can lower the reception by at least -10 dB, but it normally just pairs up with concrete or brick, which is usually the main material under the layer of plaster. What materials can block a wifi signal? Not plaster, sorry. 

8. Concrete and cement

This is the heavy artillery of signal blocking. Concrete is an irreplaceable building material, but it’s one of the main enemies when it comes to blocking cell phone signal and wifi signal. Concrete is thick and dense, so no surprise there. It’s one of the main reasons for urban areas to have trouble with indoor signal and loose up to -30dB. 

9. Brick

To answer the question of what can interfere with cell phone signal,  brick is definitely one of the offenders. It’s very sturdy and makes an excellent building material obviously, but its sheer thickness and density are affecting the signal strength in a negative way and can drop reception by almost -30 dB. As we mentioned before, brick usually has additional layers of plaster and paint, so it slows down all kinds of signals, cellular and wifi as well. And talking about paint, does lead paint block wifi? The answer is yes, absolutely. It can cause difficulties for the wifi signal to get through. 

10. Low-E glass and tinted glass

Tinted and low-E glass do a great job at preventing heat and UV light from getting in, but unfortunately, it’s very good at reflecting all kinds of cell signals. It is very heavily used in urban areas and creates that modern futuristic look that we are all accustomed to. But it creates the necessity for many office buildings to have a system of signal boosters installed, as it is one of the main reasons for blocked signals in cities and will lower the reception by as much as -40 dB. 

11. Metal

We finally arrived at the last and most serious signal blocker on the list. It’s obviously metal in all shapes and forms. Does the metal wiring affect wifi signal? Yes. Do metal roofs interfere with cell phone reception? Absolutely! If you have a metal roof cell phone reception can drop significantly for as much as -50 dB. Aluminum, copper, iron, and many other metals are excellent signal blockers. So if that’s your purpose (there are situations that call for it), go ahead and use it in abundance. Despite the fact that metal roofs and cell phone reception don’t really go hand in hand, having metal in the roof lining is not a death sentence for your signal. There are things you can do, like getting a cell signal booster or switching providers. 

Conclusion 

As you can see, there are many different reasons for decreased cell signals, but none of them condemn you to run outside every time you have to take a call. There are things you can do, and devices that can help, so don’t despair! Suppose you are in the process of construction, or planning, consider mapping the designated area to determine whether you have dead zones or low signal spots around. In that case, that will help you to avoid surprises later on. Stay connected and good luck!