After fifteen years of WiFi callouts across London, I'd estimate ninety per cent of what I see falls into about ten patterns. The street name on the job sheet changes; the underlying problem doesn't. So I've written up the lot — the ten most common WiFi problems London households and small offices ring me about, with the actual fix for each. If you recognise yours in here, you've saved yourself a callout and possibly a wasted Amazon order.

1. The dead spot upstairs

The single most common job in my diary. Router on the ground floor, usually near the front door because that's where the master socket is, and the front bedroom upstairs gets one or two bars. The 5 GHz radio drops off entirely; the 2.4 GHz radio is just about audible but useless for anything modern. People try every router setting in the world. None of them help, because the problem isn't the router — the problem is that 5 GHz WiFi loses roughly 4–6 dB through every interior wall and most of a ceiling joist run, and you've asked the signal to clear two of them.

The fix is almost always the same: get a transmit point upstairs. A single ceiling-mounted or wall-mounted access point on the landing, fed by a Cat6 from the router downstairs and powered over PoE. That's it. Done properly the signal reaches every room on that floor with zero handoff issues. Plugged-in range extenders trying to relay the downstairs router's signal through the same wall? They almost always fail — and I've written about that at length in why WiFi boosters and extenders almost always disappoint.

2. The basement kitchen dead spot

Big across the Victorian terraces of Battersea, Brixton, Stoke Newington and most of west London. The kitchen has been knocked through and the family lives down there; the router is upstairs in the hallway. Add a steel RSJ over the kitchen-extension threshold, a concrete-screed floor with underfloor heating, and you've built a brilliant Faraday cage between the router and where everyone actually is. Phones drop to LTE the moment you walk down the kitchen stairs. The smart speaker on the worktop says "I'm having trouble connecting to the internet."

Same fix as the dead spot upstairs, mirrored downwards. Cat6 cable to the basement — usually fished through an old gas-pipe knockout or the boiler-cupboard wall — and an access point at ceiling height in the kitchen. The point about ceiling height isn't aesthetic: WiFi radiates strongest perpendicular to its antennas, so a high-mounted AP spreads the signal across the room horizontally rather than firing the best part of it into the cooker. See the ethernet cabling page for what's involved.

3. "WiFi drops every evening around 7pm"

This one isn't a coverage problem at all. It's a channel-congestion problem. London is the densest WiFi environment I've ever measured; I've stood in a fourth-floor flat in Marylebone and counted ninety-two visible networks on the 2.4 GHz band. Around 7pm, every household within range turns on their televisions, their smart speakers, their kids' tablets and their robot vacuums. The radio environment goes from manageable to chaotic.

The fixes, in order of impact:

  • Stop using 2.4 GHz where possible. Force phones, laptops and TVs to 5 GHz, where there are far more usable channels and far fewer neighbours.
  • On the router, fix the channel rather than leaving it on "auto" — and choose a channel from the DFS block (52–144) on 5 GHz, which most consumer routers ignore.
  • Drop the channel width on 5 GHz from 80 MHz down to 40 MHz if the channel is congested. Narrower channel, fewer collisions, steadier throughput.
  • If the router is 802.11ax (WiFi 6) capable, enable BSS Color in the settings. It lets the router transmit through neighbour traffic rather than backing off. A free fix, and the single biggest improvement I've seen on dense streets.

If your kit is older 802.11n or 802.11ac with no BSS Color and no DFS support, you can tune the channel manually as far as you like and you'll still hit a ceiling on a Friday evening. That's the point at which an actual WiFi installation with a current standard pays for itself.

4. The one device that won't connect

Five devices on the WiFi happily, one refuses. Always the same one. This is rarely a router problem — by definition the router is working, because everything else is on it. It's almost always device-side. The common causes:

  1. The device is a 2.4 GHz-only gadget (smart plug, doorbell, older Echo) and it's trying to connect to a network broadcast on 5 GHz only, or to a band-steered combined SSID that's failing to hand it down.
  2. The device has a stale DHCP lease and the router has reused its IP for something else. Reboot the device first, the router second.
  3. The device is on a recent OS that's been told "use random hardware address" and the router's MAC filtering or guest-network logic is rejecting unrecognised MACs. Turn off the random-MAC setting for that specific network in the phone's WiFi advanced settings.
  4. The device is older than 802.11n and the router is set to "WiFi 6 only" or "WPA3 only." Some kit doesn't negotiate down gracefully.

If it's a smart-home device specifically, set up a dedicated 2.4 GHz-only SSID with WPA2 (not WPA3) and a simple password, then connect the device to that. Saves hours.

5. "WiFi works fine near the router but not in the back room"

The honest physics answer. WiFi is a radio signal and radio signals get weaker through brick, plaster, foil-backed insulation and metal. There's a separate post on what actually blocks your WiFi signal with the dB numbers if you want them, but in short: by the time the signal has been through a kitchen back wall and a brick chimney breast, even a brand-new router has very little left to give the back-room laptop.

The fix is the same as it always is when distance and walls are in the way: don't try to push more power through the obstacle. Put the transmitter on the other side of the obstacle. One Cat6 run, one access point, problem gone for the next ten years.

6. Garden and patio coverage

The London summer makes this a seasonal callout. Family wants to work from the patio, kids want WiFi at the bottom of the garden, the smart irrigation controller in the shed has stopped reporting. External walls are usually worse for signal loss than internal walls — solid London brick, sometimes a layer of foil-backed insulation board added during a recent re-render, sometimes double-glazed bifold doors with metallised low-E coating that act as a partial signal mirror.

The right approach is an external-rated WiFi access point under a soffit, eaves or covered terrace, fed by a Cat6 from inside the house and PoE-powered so there's no outdoor mains. The wrong approach is an indoor router on the kitchen island fired hopefully through the patio doors. The first works in any weather for years; the second works for the first three metres and dies in the rain.

7. Smart-home devices keep dropping

Closely related to problem 4, but with a twist. Smart-home gear lives on the 2.4 GHz band almost exclusively, and 2.4 GHz is the most polluted radio band in any London home. It's not just other WiFi networks — it's microwaves, baby monitors, older Bluetooth devices, certain LED strip controllers, and occasionally a very specific cause: the inverter motor in a modern fridge or washing machine.

I had a job in Hampstead earlier this year where the lights in the kitchen had stopped responding to Alexa, intermittently, around dinnertime. The customer had assumed it was the router. Walked round the house with a spectrum analyser and the noise floor on 2.4 GHz channel 6 spiked every time the family's American-style fridge compressor cycled — the inverter was leaking RF into the band. Moved the smart-hub onto a 2.4 GHz channel 11 with a different overlap, narrowed the hub's WiFi channel width, and the problem evaporated. The router had nothing to do with it. The fridge was the WiFi problem. That's the kind of diagnostic you can't do without instruments — see WiFi heat-map survey for what a proper survey looks like.

8. Guest network confusion

This isn't really a "WiFi problem" but it comes up enough that I'll include it. People set up a guest network, forget about it, share the wrong QR code with their cleaner, and then wonder why their guests can see the smart speakers and their cleaner can't open the door lock app. Two rules that solve ninety per cent of guest-network frustration:

  • Name your main network and your guest network clearly different things. "Home" and "Home_Guest" is fine. "Two-character difference" is not, because half your guests will type the main password into the guest SSID and assume it's broken.
  • Decide consciously whether the guest network has device isolation on. If you want the visitor's phone to be able to cast to your TV, isolation off. If you want maximum security, isolation on. Most routers default to isolation on, which is fine for most households.

9. "Fast internet, slow WiFi" — the misdiagnosis

The most common framing I hear on the phone. Customer rings the ISP, ISP runs a line test, says the line is fine, suggests it must be the WiFi, customer rings me. Sometimes that's the right diagnosis. Often it isn't.

The test I do on every job, before I touch anything: plug a laptop directly into the router with a known-good cable and run a speed test. That's the line speed. Then run the same test on WiFi, two metres from the router. If that number is reasonably close to the wired one, the WiFi at that spot is fine. If it's vastly lower, the WiFi radio (or its configuration) is the issue. Then walk to the slow room and run it again. The difference between "fine here, terrible there" and "terrible everywhere" tells you instantly whether you're solving for coverage, contention or a saturated WAN. I've written about this from the line side on the London broadband engineer page — the diagnostic process is half the job.

The other half of "fast internet, slow WiFi" is that the customer has a beautiful 900 Mbps full-fibre line and expects to see 900 Mbps on a phone three rooms away. That isn't a WiFi problem; that's an expectation problem. No consumer WiFi delivers the full line speed in a back bedroom — and even if it did, no single device is using that speed for anything except a speed-test app.

10. Small-office conference-room blackspots

The bane of every small London creative or professional services office. The main floor has good WiFi because that's where the router is. The conference room — usually a glass-walled box at the far end, often with metallised privacy film on the glass — drops to one bar and Zoom calls go to mush ten minutes before the client arrives.

The cause is almost always the same: only one access point in the office, and it's placed for the desks, not for the meeting rooms. Glass walls aren't a problem in themselves but metallised film and steel partition frames are. The fix is a dedicated AP on the conference-room ceiling, wired back to the main switch with Cat6, PoE-powered, on 5 GHz with a clean DFS channel. The conference room becomes the best WiFi spot in the building, which is exactly what you want when the client is in the chair.

Three jobs from this year that fit the patterns

Hampstead family — the smart fridge

Mentioned above. Late-Victorian terrace, two parents working from home, two children, all the usual smart-home kit. The complaint was "WiFi drops every night around dinner." The customer had already bought a mesh system, fitted it themselves, and the problem hadn't moved. The spectrum analyser showed the noise floor on 2.4 GHz lifting by twelve dB every time the fridge compressor cycled. Pulled the smart-hub onto 5 GHz where it would talk to the cloud, kept the 2.4 GHz Zigbee mesh, isolated the WiFi band the hub used to channel 11. No more drops. Nothing to do with the mesh kit or the router — it was a kitchen appliance polluting a radio band. Without measurement we'd have been changing routers forever.

Soho creative agency — the missing 5 GHz

Twelve-person agency above a restaurant on Dean Street. The main floor was fine — old-but-serviceable 802.11ac AP in the ceiling — but the rear conference room was a black hole. They'd tried a powerline adapter and a desktop range extender. Neither helped, because the AP they were trying to extend was already weak in that room. We replaced the existing AP with a WiFi 6 dual-band PoE access point on the main floor and added a second WiFi 6 AP in the conference room, wired through the suspended ceiling on a Cat6 run that took an afternoon. New PoE switch in the comms cupboard. The conference room now tests at 450 Mbps to the router, the main floor at the same, and seamless roaming between the two means the MD's laptop doesn't drop when he walks between them mid-call. Same broadband line throughout — we never touched that.

Tooting terrace — one PoE access point upstairs

Three-bedroom Edwardian terrace off Tooting High Street. Family had spent two years cursing the WiFi in the back bedroom. Router was in the front hall on the master socket, as always. The back bedroom is up a flight of stairs, behind a chimney breast and a load-bearing wall, separated from the router by something like fifteen metres of brick and timber. WiFi 5 router from the ISP, perfectly adequate, just couldn't possibly reach.

One Cat6 run up through a stair-cupboard backing, terminated to a single ceiling-mounted PoE access point on the landing. Half a day on site. Speed in the back bedroom went from ~6 Mbps to 280 Mbps. We left the original ISP router alone — there was nothing wrong with it, it just couldn't be in two places at once. This is far and away the most common pattern across the London terraced housing stock: one router, one wire, one well-placed access point on the floor above. See mesh vs wired access points for why that approach beats mesh for the typical Victorian/Edwardian floor plan.

The diagnostic order I follow on every callout

If you want to try this yourself before booking anyone, here's the same sequence I use:

  1. Test the line wired into the router. Establish the ceiling.
  2. Test WiFi two metres from the router. Establish whether the radio is healthy at all.
  3. Test WiFi in the worst room. Establish the gap.
  4. Count visible neighbour networks on 2.4 and 5 GHz. Establish how dense the radio environment is.
  5. Look at the position of the router. If it's on the floor, behind a TV, inside a metal cabinet, in the hallway with two thick walls between it and the living areas — that alone explains most coverage issues.
  6. Identify any chronic offenders — a broken IoT device flooding the network, a microwave, an old USB 3 dock that radiates on 2.4 GHz, a fridge.
  7. Only then consider replacing kit. The cheapest fix is almost always a wire and a well-placed access point, not a new router and not a new mesh system.

The flats and houses I work in are full of WiFi that's been "fixed" by previous occupants buying ever-more-elaborate consumer mesh systems. Half of them are still plugged in. The other half are in a kitchen drawer. The kit isn't the answer; the cabling and the placement are. See WiFi in London apartments and conversion flats for the specific challenges of mansion blocks, ex-council flats and conversion floor plans — and the master sockets page for why the location of your incoming line is often the source of half your trouble.

When to ring an engineer

You can solve a surprising amount yourself: move the router, fix the channel, separate 2.4 from 5 GHz, force smart devices to a dedicated SSID, get rid of any extenders that aren't working. When to call someone in: when you've tried the above and you've still got a dead spot, when you need cable run between floors, when the office has grown beyond what a single AP can cover, or when you've simply had enough and want it solved properly. Most jobs are a day, sometimes less. Most fix the problem for the lifetime of the house.

Ring 020 3633 1131. Honest advice, freely given.