The network is the first system
Every other discipline in the house rides on top of the network. It is the system nobody asks for and the one everybody notices the day it is wrong.
Nobody has ever walked into a showroom and asked to be shown the network.
They ask about the cinema, the lighting, the way the music follows them through the house. The network is the thing underneath all of it, and the only one of them that, when it falters, takes the other five with it.
In a significant home it is also the discipline most often left to the end, specified by whoever is cheapest, and then asked to carry a load nobody sized it for.
What actually breaks
The complaint is almost never "the network is down". It is more specific and more annoying than that.
The far bedroom drops off at night. The camera at the gate goes grey for ten seconds and comes back. The cinema buffers on the one evening the house is full. The blinds respond, but a beat late, and only on that side of the house. Somebody has added a device and now something else is unhappy.
Every one of those reads as a fault in the system it appears in. The lighting is blamed, or the cinema, or the cameras. The cause is underneath.
Three things decide it, and two are free
Where the access points sit. This is a drawing problem. An access point is a radio, and a radio is defeated by what sits between it and the device: double brick, rendered foam, concrete slabs, foil-backed insulation, a lift shaft, a wall of glazing that the garden sits behind. In a house with a basement, a first floor and a studio at the end of the garden, the positions that give even coverage are not the positions that are convenient, and they are almost never the ones left over at the end.
Working this out on a plan costs nothing. Working it out afterwards costs access points nobody needed and a result that is still uneven.
Where the cable goes. The honest answer to most coverage questions is cable in the right places, not more equipment. A wired access point in the correct position beats three wireless ones in convenient ones, every time, and it is cheaper. But a cable has to be run before the linings go on, which means the answer has to exist at prewire, which means the question has to be asked at design.
What it has to carry. Not the number of people. The number of devices, which in a large household is routinely over a hundred once the cameras, the controllers, the blinds, the pool plant, the televisions, the audio zones and the family's own phones and laptops are counted. Most of them are small and constant rather than large and occasional, which is a different load from the one domestic equipment is sold against.
Why mesh is not the answer in a rendered house
Mesh systems work. They work well in apartments and in lightweight construction, and they are an honest product for that job.
What they cannot do is get a signal through the materials significant homes are built from. A mesh node relays what it receives, so a node that sits in a weak spot relays a weak signal. Add nodes and you add relays, each one halving the throughput available to the next. In a double-brick house with a rendered extension and a concrete suspended slab, the second node is often already struggling to hear the first.
The result is a house that tests fine standing next to the router and disappoints everywhere a person actually sits.
What it looks like when it is designed
Access point positions marked on the reflected ceiling plan, alongside the lighting, so they are coordinated with the downlights rather than argued with afterwards. Cable runs to each one, documented and labelled at both ends, run at prewire. Hardware sized for the device count rather than the floor area. Separate networks for guests, for the household, and for the equipment that runs the house, so a visitor's laptop and the camera recorder are not on the same segment.
And a position in the rack that was drawn rather than found, with somewhere for the heat to go.
Coverage is a design problem before it is a hardware problem.
The outbuildings question
It comes up on almost every Peninsula property and it is worth answering early, because the answer is usually a trench.
A studio that was a shed. A pool house. A gate at the end of a long drive. A garden that gets used properly in summer and wants audio and cameras in it. None of those are reached reliably by wireless, whatever the box promises, and all of them are trivial to serve if a conduit went in while the landscaping was still being dug.
Ask the question at concept and it is a line on a drawing. Ask it after the driveway is poured and it is a different conversation.
The part that matters years later
A network designed properly is also a network that can be added to. A camera at a new gate, a zone in a building that was a shed, a second access point when the garden starts getting used. A home with cable in the right places and spare capacity in the rack absorbs those in an afternoon.
It is also the reason remote support works at all. A system that can be reached, read and understood from a distance gets fixed on the call. One that cannot gets a van, a day, and a conversation about who is paying for it.
None of which anyone thinks about while the house is being drawn. Which is exactly when it has to be decided.