What Materials Block Wi-Fi Signals? (And How to Fix It)

The Scoop | 18/07/2025

If you’ve ever watched your signal strength vanish the moment you step into another room or wondered why the upstairs bedroom is a Wi‑Fi dead zone, you’re not alone. The issue might not be your broadband, it could be your walls.

In this guide, we’ll dig into the materials that block Wi‑Fi signals, explain why it happens, and show you how to fix it. From sneaky signal-sappers like mirrors and fish tanks to concrete walls and foil-backed insulation, we’ll help you understand the invisible battle happening in your home, and how to win it.

Why some materials block Wi‑Fi (and others don’t)

Wi‑Fi works by sending out radio waves, usually in the 2.4 GHz or 5 GHz range. Like all waves, they can be absorbed, reflected, scattered, or even completely blocked depending on what they hit.

Here’s what can happen:

Absorption: Some materials soak up signal strength like a sponge, turning your Wi‑Fi energy into heat. Thick concrete, water, and metal are classic absorbers.
Reflection: Shiny surfaces like mirrors and metallic coatings bounce signals away, often in the wrong direction.
Scattering: Uneven or layered materials break the signal up, weakening it.
Diffraction: When signals try to bend around an object, they lose strength in the process.

So if your home is made of certain materials, or filled with them, your Wi‑Fi could be taking quite a beating before it reaches your device.

The worst Wi‑Fi blockers and how they affect your signal

Let’s break down the most common offenders and how they mess with your Wi‑Fi:

Metal: Metal reflects Wi‑Fi signals like a mirror. Whether it’s a filing cabinet, fridge, radiator, or even foil-backed plasterboard, metal disrupts your connection by deflecting signals or absorbing them entirely. If your router is sitting next to a stainless steel fridge, for example, don’t be surprised if the signal drops off sharply behind it. Even things like aluminium blinds or steel beams inside walls can interfere.
Concrete and brick walls: Dense, solid materials like concrete and brick are major obstacles for Wi‑Fi. Especially reinforced concrete, which contains metal bars inside. These materials absorb and weaken the signal significantly. If your home has thick internal walls or multiple floors with concrete in between, you might experience signal degradation.
Mirrors and low-E glass: Mirrors often contain a thin layer of metal on the back, which reflects Wi‑Fi signals away from where they’re needed. Low-emissivity (Low-E) windows are designed to reflect heat, but they also reflect radio waves, acting as unexpected signal barriers between rooms or across your garden.
Water: Fish tanks, water heaters, or even human bodies can weaken Wi‑Fi. Water absorbs radio waves very effectively, especially at 2.4 GHz. A large aquarium between your router and your devices? That’s a Wi‑Fi black hole.
Ceramic tile and plaster: Individually, these don’t block much. But tile is often laid on concrete or brick, and plaster adds another layer of density. Together, they can subtly sap your signal, especially in bathrooms and kitchens.
Wood and drywall: Wood, plywood, and drywall have a relatively low impact on your Wi‑Fi, but when combined across several walls or floors, the signal loss can stack up. Think of it like walking into a forest. One tree’s no problem. Twenty trees? You start to lose visibility.
Plastic and foam insulation: Some dense plastics (like polyethylene or polystyrene) can absorb Wi‑Fi to a degree, particularly if they’re part of thick insulation or furniture. If your walls are packed with foam, or your furniture is built from dense plastic, it could be contributing to signal fade.
Foil-backed plasterboard and paint: Foil-lined drywall is one of the worst offenders. It can completely block Wi‑Fi and even mobile signals. Some specialist paints designed to block EMF (electromagnetic fields) do the same. These materials are often used in new builds or home offices.

Other things that interfere with Wi‑Fi

It’s not just walls. A few everyday items can wreak havoc on your connection without you realising:

Microwave ovens: Operate on the same frequency as 2.4 GHz Wi‑Fi. If your connection drops when someone heats up leftovers, now you know why.
Bluetooth devices: These also use the 2.4 GHz band and can cause interference, especially if there are lots in use.
Christmas lights and fairy lights: Twinkling lights with metal wiring can build up enough electromagnetic interference to affect nearby routers.
Neighbouring Wi‑Fi networks: Competing routers on the same frequency or channel can slow things down. Urban flats? This is a common one.

Fixes and workarounds: How to keep Wi‑Fi flowing

The good news? You don’t have to knock down walls to get a better connection. Try these smart solutions:

Move your router: Place it in a central, elevated location, away from thick walls, metal, and appliances. Avoid corners and cupboards.
Use both 2.4 GHz and 5 GHz bands: 2.4 GHz travels further and penetrates better, but 5 GHz offers faster speeds. Most modern routers support both. Use them strategically.
Install a mesh system: Instead of relying on one router to cover your entire home, a mesh setup uses multiple nodes placed around the house to spread the signal evenly. This approach works around walls and blockers, filling in dead zones with fresh coverage. Our GoFibre routers support mesh networking and can be connected with additional routers to create a seamless network. Check out Enhanced Wi-Fi to add extra router nodes and expand your coverage.
Avoid placing routers near metal or water: Keep clear of fridges, aquariums, and metal shelves. Even a microwave nearby can throw things off.
Use wired connections for static devices: Devices like desktop PCs or gaming consoles can benefit from Ethernet connections, freeing up more Wi‑Fi for mobile devices.
Upgrade your router: Upgrading your router can make a big difference. Modern routers come with stronger antennas and smarter technology that can boost your signal range and stability. Dual-band or tri-band routers give you more options, letting you switch between 2.4 GHz (which travels farther and penetrates better) and 5 GHz (which delivers faster speeds but over shorter distances). If you are a GoFibre customer, you can upgrade to the GoFibre’s Advanced Router.
Test your signal: Walk around your home with a internet speed test to identify dead zones, and adjust your setup accordingly. If you are a GoFibre customer, you can easily run speed tests from the GoFibre app.

If your Wi‑Fi signal is strong in some rooms but disappears in others, your walls or even what’s hidden inside them could be the reason. With the right setup, smart placement, and upgraded technology like a mesh system or a better router, you can turn those dead zones into fast lanes and enjoy ultra-reliable internet in every corner of your home.