Trusted Reviews is supported by its audience. If you purchase through links on our site, we may earn a commission. Learn more.

How to build a smart home extension

Most smart homes are the product of add-ons, modifying an existing house and bolting in smart lighting, heating and more. The result can be a mismatch of products and an ugly-looking finish. When you’re starting from scratch and have the walls and floors up, things don’t have to be that way. We will show you how to build a smart home extension and what you need to plan for.

The key point here is to overspecify – as you never know when you might need something later down the line, it’s better to have and not need, and all that.

Put Ethernet everywhere

While Wi-Fi has certainly improved with the likes of mesh systems boosting wireless speeds throughout your home through additional wireless access points, it’s still not perfect. And even mesh networks reach their limitations and, such as the Netgear Orbi RBK50, benefit from using Ethernet to connect up the satellite access points. In all cases, having a physical connection to a device, be it a smart home hub or media streamer, is more reliable than using wireless only.

Related: Best Wi-Fi extenders

I fully recommend putting in as much Ethernet as you can around your new extension. There are several areas to focus on. First, is the main connection to your router. Most routers have three or four Gigabit Ethernet ports, which at first seems quite limiting.

However, you can boost the number of points by connecting Gigabit Ethernet switches to your router. A simple eight-port Netgear ProSafe GS108 costs around £30, but gives you additional wired capacity.

You can daisy-chain switches together, but be careful about overdoing it. The final connection to your router and, therefore, the internet is a single Gigabit Ethernet cable. If you daisy-chain too many devices, you’re introducing a bottleneck. That said, it may be convenient to extend access through a second switch in some cases, particularly to low-bandwidth devices, such as smart home devices.

In my home, I have three switches in the main house. One is behind the TV and is for all of the media devices there, including Sky Q, an Ultra HD Blu-ray player and the TV. This switch is directly connected to the router.

A second switch is placed under the floor at the back of the house and serves for the kitchen extension. This is connected directly to the main router but has a daisy-chain link to a third switch, located in the hall cupboard, that serves as the home for the smart home hubs. Plan where you want your switches to be located as, ultimately, you’ll need to run Ethernet cables to them.

Build a smart home extension switch in a box

There are two ways to run Ethernet: run a patch cable and poke it out a hole in a wall or floor, or terminate the run at a wall socket that you plug a separate cable into. The first is the easiest and dirtiest: you just run a patch cable. Cat 5e will deal with Gigabit Ethernet, but go with Cat 6 if you want future support for 10Gbit Ethernet. Cables are quite cheap, with a 10m Cat 6 cable costing less than £10. You can have a maximum of 100m of cabling, but 50m should cover the longest length you’ll realistically need.

Running a patch cable means that you have a connector on either end, which doesn’t look very neat. However, this doesn’t always matter. For my cupboard with smart home hubs, I have a cable come up out of the wall and connect into a switch. As the cable’s in a cupboard, you can’t see it, so there’s no need to terminate it neatly. Having a place for smart home hubs is really handy, particularly as the cupboard is roughly in the middle of the house, giving decent coverage.

Build a smart home extension hubs in a cupboard

Likewise, under a run of kitchen cabinets, there’s another cable, which can’t be seen. This plugs into the hub that runs the smart cat flap (a SureFlap Microchip Pet Door Connect) and is a good use of space.

Particularly when building a kitchen, think about using the under-cabinet space for such devices, but stick away from any areas that could be exposed to water, such as under the sink or the dishwasher.

Think about running Ethernet upstairs through any voids that you might have. I have a cupboard upstairs that houses the boiler and is just above the kitchen. While the work was being done, this gave me a perfect opportunity to run a cable into this cupboard, hooking up the Orbi RBK50 via Ethernet.

Build a smart home extension kitchen plinth

The second way of running cables is neater. Terminating in a wall-mounted socket, you avoid unsightly cables poking out. Instead, when you want to use a port, you just plug a shorter cable into the wall socket and the device you want to use. I have a Sky Q Mini box plugged into a port in the kitchen.

When terminating the socket, you’ll need a cable to be run to a pattress box, and then terminated in an RJ45 female connector. An Ethernet crimping tool is used to make the connection. It’s often easier to buy a run of patch cable, then snip the end off and re-terminate in the socket.

For even easier convenience, try a Quick Connect box from Nexxia: you just plug a patch cable into the rear and you’re done, with no additional wiring. The downside is that these connectors are a little deeper, so you’ll need a pattress box deep enough.

Build a smart home extension Ethernet switch

Place as many connectors around your new extension as you think you might need. If you know where you’re going to put a TV or desk, place sockets there; don’t be shy about placing an extra socket or two elsewhere: you never know when you may move things around.

Height is important. You can place the sockets at the traditional level near the floor, but that may not work for all applications: with a wall-mounted TV, for example, a higher-level Ethernet socket could be really useful; I wish I’d done this in my kitchen.

In all cases, you end up with a bunch of Ethernet cables or sockets at the points you need to use them, with the other ends collated near the switch. Don’t worry if you end up with more cables than you have switch ports for, as you don’t need to connect up everything, just the cables that you’re actually using. For this reason, labelling the cables can be useful.

My way of doing things is to have a top-down diagram of the new area, which I mark up with numbered Ethernet ports. To match the cables with the numbers (if you didn’t at the start), I start by unplugging all cables from the switch. Then, I plug a laptop (any device will do) into the end of an Ethernet cable or wall socket (the opposite end to the switch) starting a port 1.

At the switch end, I plug and unplug cables until a port lights up: this shows there’s a connection, and the cable can be labelled as port 1 using a bit of masking tape. Repeat with the other cables until you’ve done the entire run.

Plan your smart lighting

Smart lighting can transform a space, particularly if you go with colour-changing bulbs, such as with the Philips Hue, as I did. As you can see from the images below, the kitchen can take on completely different looks and feels, just by adjusting the colour. It really is the final wow factor, in my opinion.

Build a smart home extension internal lights

I went with Philips Hue for two reasons: there’s a wider choice of bulb fittings, and there are dedicated remote light switches, so the lights can be operated as ‘normal’ without using an app or a voice assistant, such as Alexa. However, these options remain a valid form of control.

For me, smart lighting is about the effect – rather than necessarily seeing the lights – so we had the kitchen built to house these products without them being seen. Spotlights (GU10s) sit out of sight in the side of the original building. Around the skylight, we had a small shelf built, which the LED strip is connected to (you can run up to 10m of lighting in this way). This gives illumination, but you mostly don’t see the LED strip and it also lights up the outside of the house.

Build a smart home extension Philips Hue Light Strip control box

The Hue LED strip is powered by a plug-in power adaptor. Normally installations can be a problem, but not in this case, as we had a power socket installed in the top of a kitchen cupboard and just ran the cable through the newly-built ceiling into the cupboard. Again, it’s worth thinking about where you may need sockets. In my setup, only two main bulbs are visible inside the housing that we picked for them.

Build a smart home extension plug in a cupboard

Control of the lights is via a Hue Switch, which connects magnetically to the fridge on the way into the kitchen. The middle section can be removed and used as a remote control. However, just in case something goes wrong (or I move and want to take the bulbs), there are dedicated normal light switches. By default, these are left on and never touched. Hue is smart and in the event of a problem, turning the switch off and then back on again turns the bulbs on, with them set to warm white.

Build a smart home extension Philips Hue Dimmer

Outside, the garden office already had GU10 up and downlighters. I mirrored these on the extension, kitting them all out with Philips Hue White Ambience (temperature-changing bulbs), hooked up to another Hue Switch. So, now, the garden and kitchen both operate with smart lighting.

Build a smart home extension external lights

Related: Amazon Alexa guide

Plan smart underfloor heating

If you’re going to put in underfloor heating, then you need to place the heating manifold somewhere sensible. While you’re doing it, it makes sense to think about underfloor heating. I run Honeywell Evohome in my house, which is compatible with underfloor heating.

A Honeywell Single Zone Thermostat Y87RF2024 did the job, with a T87RF2033 Wireless Thermostat for temperature measurements and a BDR91 Wireless Relay Box to control the underfloor heating manifold. This just adds an additional zone into the house, which is as controllable and programmable as any other room.

Build a smart home extension Thermostat

Related: Best smart thermostats

Work out where your smart speakers and audio are going

If you want audio around your home, then think about what you can do with the walls opened up, and you can run cabling. I opted for two high-level power sockets on either side of the room: one each for a Sonos Play:1 speaker that I mounted on the wall. There’s also a Sonos Sub located under the kitchen counter for bass. The beauty of doing things from scratch is that everything is hidden.

Build a smart home extension Sonos One

An Amazon Echo Dot sits above the wall-mounted TV, powered by the USB port on the back of the Sky Q Mini box. I overcame the lack of power points at TV height by using a multi-way adaptor behind the TV.

I also had a speaker cable run along and out of the back of the extension, wall-mounting weather-proof speakers outside. These are connected to a Sonos Amp, which is sat in a box under the old dining room floor: there’s little need to see a Sonos player like this. In the summer months, it means quality outdoor music, which I can also play inside – no more messing around with Bluetooth speakers.

Build a smart home extension outdoor speaker

There is one area where you’ll have to make a choice. I mirrored the outdoor speakers to the Sonos Play:1 speakers inside. Typically you pick the left and right speakers by standing and looking at them. However, standing inside and looking out is the mirror image of standing outside and looking inwards at the outdoor speakers. In my case, it would mean that the left indoor Sonos speaker was next to the right outdoor speaker and vice versa. My advice, if you end up in a similar situation is to match the outdoor to the indoor, so left is next to left, and right next to right.

What else to look out for

Make sure you have plenty of power sockets and areas to put things. I have a Dyson 360 Eye robot vacuum cleaner that keeps the kitchen looking neat and tidy. A lower-level power socket and a slightly shortened run of cupboards gave plenty of room for the cleaner to sit out of the way when it’s not in use.

Related: Best robot vacuum cleaners

Got any more tips or tricks for dealing with a new-build? Tell us @trustedreviews

Why trust our journalism?

Founded in 2003, Trusted Reviews exists to give our readers thorough, unbiased and independent advice on what to buy.

Today, we have millions of users a month from around the world, and assess more than 1,000 products a year.

author icon

Editorial independence

Editorial independence means being able to give an unbiased verdict about a product or company, with the avoidance of conflicts of interest. To ensure this is possible, every member of the editorial staff follows a clear code of conduct.

author icon

Professional conduct

We also expect our journalists to follow clear ethical standards in their work. Our staff members must strive for honesty and accuracy in everything they do. We follow the IPSO Editors’ code of practice to underpin these standards.