Smart home wiring: what should I put in at first fix?

What does first fix actually decide for a smart home?

First fix is the point in a build or renovation when cables go into the walls, floors and ceilings before they are closed up. Everything that runs inside the fabric of the house goes in now. Everything that does not is a surface run or a chase and a repair later.

For a smart home that matters more than for an ordinary one, because most of what makes a house smart is not the devices, it is whether the wiring gives those devices what they need. A dimmer that wants a neutral and does not have one, a wifi access point with no cable to it, a blind motor with no supply in the window reveal: these are the failures we get called to after the plaster is on, and every one of them was a few metres of cable at first fix.

So the job at first fix is not to choose a system. It is to make sure any system will work.

Why does every switch need a neutral?

Because nearly every smart switch, dimmer or relay needs a small amount of power all the time to run its own electronics and stay connected, and it gets that from a neutral conductor at the switch. Traditional UK lighting was wired without one: the switch just breaks the live, and the neutral goes straight to the light.

Two-wire smart switches that work without a neutral exist, and they are a compromise. They leak a trickle of current through the lamp to power themselves, which is why LED lamps flicker or glow faintly when off, and why the list of compatible fittings is short. A neutral at the switch removes the whole problem and it costs almost nothing at first fix.

The other half of this is depth. Smart accessories are bulkier than plain ones, and a 25mm back box that suited a rocker switch will not take a module behind a smart one. We fit 35mm or 47mm boxes at every switch position as standard on these jobs, and it saves a lot of swearing at second fix.

Where should the data cable go?

More places than people expect, and all of it back to one point.

• Every room. At least one data point per room, two in the living room and the office. It is a few metres of cable and it means a TV, console or desk never depends on wifi.
• Ceiling points for wifi. One access point per floor, roughly central, wired back with data cable and powered over it. This is what a good wifi installation is, and it is why the one router in the hall never covers the back bedroom.
• Doors and gates. A cable to the front door for a video doorbell, and to the gate if there is one. Battery doorbells are a compromise for houses that missed first fix.
• Outside. Cameras want a cable, not a wifi signal through a brick wall.
• The plant. Boiler or heat pump, hot water cylinder, solar inverter and battery. All of them now report over a network and all of them are in the worst wifi spot in the house.

The central point is a cupboard, a corner of the utility, or a small enclosure under the stairs, with power, ventilation and the incoming broadband brought to it. Everything terminates there on a patch panel. It is unglamorous and it is the thing that makes the house easy to change later.

Use a decent grade of cable and run it separately from the mains cable. BS 7671 has rules about segregating power and data circuits, and a data cable clipped alongside a lighting circuit for ten metres will give you a network that works badly and nobody can find out why.

What about the things I have not decided yet?

Run empty conduit to them. A length of flexible conduit from the central point to the loft, to each floor, and to the places you cannot get back to, such as behind a wall mounted TV, into a window reveal for future blinds, or to the far side of an extension, means a cable can be pulled through in ten years without lifting a floor.

This is the cheapest insurance in the whole job and it is almost never done, because it does not appear on any schedule and nobody asks for it. Ask for it.

What do we tell people not to buy at first fix?

A whole-house system from one manufacturer, before the walls are closed.

It is the honest point most installers of those systems would not print. Fully proprietary smart home systems do a lot, and when they are designed well they are excellent. But they wire the house around their own controllers, and if the company changes direction, stops supporting a product line, or you simply want to change something in five years, you are tied to them. We have seen houses where a dead controller meant no lights until a specialist could come out.

Our approach is to wire the house so that it works as an ordinary house first. Every light has a switch on the wall that switches it, with a neutral behind it. Every room has data. The smart layer, whether that is smart switches, a hub or a full control system, sits on top of that and can be swapped without touching the plaster. If the internet goes down, or the app is retired, the house still works.

That also means the decision you need to make at first fix is a small one. You do not need to have chosen the brand. You need the neutrals, the boxes, the data and the conduit. Our smart home and networking page covers what we fit on top once the walls are closed.

Is any of this notifiable, and does it need certifying?

The mains side of it is ordinary electrical work and the usual rules apply. New circuits and work in kitchens and bathrooms are notifiable under Part P of the Building Regulations, and if the first fix is part of a rewire or an extension the whole installation is certified and notified at the end. As a registered competent person we self certify and building control is told automatically.

Data cabling on its own is not notifiable, but it should still be installed to a standard and tested, because a data point that was never tested is the one that drops to a tenth of its speed and nobody knows why. We test and label every point at second fix.

What changes the price on these jobs is mostly count and distance: how many switch positions, how many data points, how far each one is from the central point, and how much of the house is open at the time. A house that is being rewired or extended anyway is the cheap moment. Doing it afterwards, in a finished house, is the expensive one.

Questions we get asked about this