Work out what you are actually up against

Almost every garden office WiFi problem comes down to three numbers: how far the building is from the router, how many walls sit in between, and what the office itself is lined with. Spend ten minutes measuring those before you spend anything.

Measure the real route, not the straight line

Walk the route a cable would actually take: out of the house, along the fence or the back of a border, up the outside of the office, in through the wall. A garden office that looks 18 metres away is often a 28 metre run once you follow the boundary. Write the number down. It decides everything later.

Check the signal at the desk, not at the door

Use a free WiFi analyser app on an Android phone, or hold Alt while clicking the WiFi icon on a Mac, and read the signal strength in dBm at the exact spot the desk will sit. As a rough guide:

• -50 dBm or better: full speed, nothing to fix.
• -60 dBm: fine for video calls and streaming.
• -67 dBm: the practical floor for a stable Teams or Zoom call.
• -70 to -75 dBm: the link stays up but throughput collapses and calls break up.
• -80 dBm or worse: unusable, whatever the bars say.

Bars lie. A phone showing three bars at -74 dBm will still stutter through a call. Run a speed test at the desk as well, and again halfway down the garden, so you know whether the signal is fading gradually or falling off a cliff at one particular point.

Find out what the office is made of

Most garden rooms built in the last decade are insulated with foil faced PIR board. That foil is a continuous metal layer wrapped around the whole building and it behaves like a Faraday cage. A single brick house wall costs you roughly 5 to 8 dB at 2.4 GHz and more at 5 GHz. Foil faced insulation can take 20 dB or more on its own, which is the difference between a usable link and nothing at all. Metal cladding, foil backed plasterboard and low emissivity double glazing all do the same thing to a lesser degree.

Here is the quick test: stand outside the office door and check the dBm, then step inside and check again. If the reading drops by 15 dB or more the moment the door shuts, the building is your problem, not the distance, and no number of extra mesh nodes inside the house will change it.

Run an outdoor Ethernet cable if you possibly can

A wired link is the only option that does not degrade. It ignores the weather, the neighbours' WiFi and the foil in your walls, and it usually costs less than a single mesh node. Gigabit Ethernet over Cat6 is specified to 100 metres of cable, which is longer than almost any domestic garden.

Buy cable that is meant to live outside

An ordinary indoor patch lead will go brittle and crack within two British winters. What you want is solid core outdoor or direct burial cable with a UV stable polyethylene sheath. A 30 metre outdoor Cat6 run covers the large majority of UK gardens and comes in at around £25, which is less than most people spend on the extender that did not work.

One thing to check before you buy: a lot of cheap outdoor cable is CCA, meaning copper clad aluminium rather than pure copper. CCA is fine for a plain data run over a short distance, but it has higher resistance and is more brittle, so it is the wrong choice if you also plan to power an access point or a camera over that same cable. If Power over Ethernet is in your plan, pay the extra for solid pure copper.

Route it sensibly

• Clipping it high along a fence or under the eaves is quickest and easy to undo if you rent.
• Burying is tidier: 450 mm down, inside flexible ducting, with warning tape laid above it.
• Keep at least 300 mm of horizontal separation from any buried mains cable, or run them in separate ducts. Interference aside, you do not want a spade finding both at once.
• Leave a metre of slack coiled at each end so you can re-terminate a connector without redoing the run.
• Drill the entry hole sloping slightly downwards towards the outside and add a drip loop, so rain runs away from the building rather than into it.

Running a data cable is not notifiable work. It carries extra low voltage and sits outside the scope of Part P, so you do not need an electrician for the cable itself. If it is going in the same trench as a new mains supply to the office, have the electrician lay both while the trench is open.

Protect the house end

A long copper run between two separate buildings can carry a surge from a nearby strike straight into whatever it is plugged into. If the run is fully exposed and over about 20 metres, an inline Ethernet surge arrestor at the house end is cheap insurance for a router that is not.

Fit out the garden office end

Getting the cable there is half the job. What you plug into it decides whether the office feels like part of the house network or like a separate, awkward island with its own password.

Use an access point, not a second router

The simplest setup is a small ceiling or wall mounted access point in the office, fed by the cable. If you only have a spare router lying around you can use that instead, but you must put it into access point mode: turn its DHCP server off, give it a fixed address in the same range as your main router, and plug the incoming cable into one of its LAN ports rather than the WAN port. Two devices both handing out addresses on one network is the most common cause of a garden office that connects but has no internet.

Give the access point the same network name and password as the house if you want your phone to roam across seamlessly, or a separate name if you would rather choose which one you join.

Power it over the same cable

Access points and outdoor cameras normally take their power over the Ethernet cable, which saves fitting a socket in an awkward spot. A single PoE injector handles one device. If the run is also going to feed cameras, a doorbell or a second access point, a PoE switch at the house end is tidier: it powers everything from one place and lets you reboot a device remotely by cycling its port. Judge it on the total power budget rather than the port count, because an outdoor access point draws roughly 8 to 15 W and a PoE+ port can deliver up to 25.5 W.

Plug the laptop straight in

Whatever access point you fit, the machine on the desk should use the cable rather than the air. A dock with a gigabit Ethernet port turns one USB-C connection into wired networking, charging and your monitors at the same time, and it takes wireless out of the equation entirely for the device that matters most.

What to do when a cable is genuinely not an option

Rented property, a concrete driveway across the route, or a landlord who says no: sometimes the cable cannot happen. These are the wireless options in the order they actually work, rather than the order they get sold.

Outdoor point to point bridge

Two small weatherproof units, one on the back of the house and one on the office, aimed at each other. They come pre-paired, take about half an hour to set up, and will hold 100 Mbps or more across a garden with clear line of sight. Budget £60 to £150 for a pair. Both ends need power and both ends need to see each other, so a mature tree in the middle of the lawn rules it out.

An outdoor access point on the house wall

Cheaper and simpler: mount a weatherproof access point on the rear wall of the house, feed it with a short cable from the router, and let it cover the garden. This works well out to about 20 metres to a building that is not foil lined. It solves the brick wall problem but not the Faraday cage problem, so check your dBm test from step one before you buy.

Mesh with a wired backhaul

Mesh systems are good at covering a house and poor at crossing a garden. Every wireless hop roughly halves the bandwidth available beyond it, so a node in a back bedroom feeding a node in the office is already two hops from the router before your laptop joins. If you own a mesh pack already, the useful trick is to feed the garden node over a cable so it becomes a wired satellite. That is a cable run again, which is rather the point.

Powerline, and why it usually disappoints here

Powerline adapters send data along the mains wiring. The catch in a UK garden office is that the supply is almost always a dedicated circuit run from the consumer unit rather than a spur off the house ring main, because that is what the wiring regulations expect for an outbuilding. The powerline signal then has to cross at the consumer unit busbar, which costs a large chunk of the throughput, and an RCD or a surge protected socket in the path can kill it entirely. Worth ten minutes if you already own a kit. Not worth buying one specifically for this.

Squeeze more out of a weak signal

If the office does get a signal and it is merely poor, the receiving end is often the weak link. Laptop and desktop WiFi cards use tiny internal aerials, and a desktop tucked under a desk is shielded by its own metal case. A USB adapter with external high gain aerials on a short lead, sat on the windowsill facing the house, can be worth 10 dB or more over an internal card. It cannot create signal that is not there, but it can turn a marginal link into a working one.

4G or 5G as a separate connection

If the office has a decent mobile signal, a 4G or 5G router with its own SIM gives the building an independent connection for roughly £20 to £30 a month. It also keeps working when the house broadband does not, which counts for something if the office is where you work every day.

Keep the connection up when the power is not

A garden office link has more single points of failure than a desk in the house. The router, any switch and the access point often sit on different circuits, and the office usually has its own RCD that will happily trip on a wet day when a mower is plugged in.

Two things are worth doing once the connection works:

• Put the router and any switch on a small battery backup. Network gear draws very little, so a compact DC battery backup will hold a typical broadband router up for several hours. Brief cuts and brownouts stop dropping your calls and you are not walking back up the garden to reboot things. Size it for the router first, since a PoE switch feeding cameras draws far more.
• Label the office circuit at the consumer unit. When the office goes dark, knowing which breaker to check saves ten minutes of guessing in a cupboard.

If the office is your main workplace, set up and test a phone tether as a fallback while everything is working. A broadband fault then costs you two minutes rather than a morning.