topic Re: What cable can I put under new floor in anticipation of Full Fibre in Full Fibre

What cable can I put under new floor in anticipation of Full Fibre

Fineman — Thu, 12 Feb 2026 19:30:04 GMT

Full fibre not coming until 2027 but house refurb is now! Entire ground floor is down to joists for a few days only. Can I future proof this by adding a fibre optic cable to the underfloor space with some extra lengths now?

Re: What cable can I put under new floor in anticipation of Full Fibre

mystreet1 — Thu, 12 Feb 2026 21:09:50 GMT

I would look at where you think the ONT will be first. It does not have to be where the router is, just needs a power supply. Then run an ethernet cable to where your router will be, if not next to the ONT. Then plan an ethernet network from the router position, hardwired is always better than WIFI. Understand that some devices can only be WIFI.

Re: What cable can I put under new floor in anticipation of Full Fibre

Baldrick1 — Thu, 12 Feb 2026 21:23:51 GMT

@Fineman

Not fibre optic but Ethernet cable. Use at least Cat 6, for real future proofing, Cat 6A or 7. Terminate the ends in fixed pattress boxes.

Re: What cable can I put under new floor in anticipation of Full Fibre

RobPN — Thu, 12 Feb 2026 21:30:58 GMT

@Fineman

If you really do want your ONT somewhere other than 'on the nearest outside wall to the fibre entry point' it'd be worth running some flexible conduit complete with threaded draw rope between relevant points.

Re: What cable can I put under new floor in anticipation of Full Fibre

Fineman — Thu, 12 Feb 2026 22:03:34 GMT

Tvm all. Wireless Router must be positioned in middle of house for long established boring reasons and probably always so. Ergo I see 2 future proofing suggestions:
A) Choose likely future ONT position on external wall now. Run best quality ethernet cable underfloor to above Router position.
B) run smooth bore conduit along similar path.

Follow-up Q's may help decide
1. Does ONT need power? Could it live behind a curtain? Approx how big?
2. If conduit, could any other future cables (cannot imagine) go in same conduit or will they interfere somehow?
TIA

Re: What cable can I put under new floor in anticipation of Full Fibre

mystreet1 — Fri, 13 Feb 2026 06:26:47 GMT

ONT does need a power supply. Rough size is 4 inches square, depth of 1 inch, and goes be hidden behind a curtain.

See this for what happens on the day.

https://www.openreach.com/help-and-support/full-fibre-broadband-installation-checklist#accordion-b43490109a-item-d91328b77e

Re: What cable can I put under new floor in anticipation of Full Fibre

Fineman — Fri, 13 Feb 2026 07:26:00 GMT

Many thanks again.
That Openreach guide implies Router close to ONT but can they be say 10m apart?

Re: What cable can I put under new floor in anticipation of Full Fibre

MisterW — Fri, 13 Feb 2026 07:48:41 GMT

@Fineman

but can they be say 10m apart?

They can easily be up to 100m apart!

Cat5e or better ethernet cable will support 1Gb at up to 100m length. To future proof, as suggested above , use Cat6 or better.

Re: What cable can I put under new floor in anticipation of Full Fibre

Dan_the_Van — Fri, 13 Feb 2026 08:05:41 GMT

How is the current copper phone line currently fed to you property, Overhead or Underground and where is the Master Socket located?

Is the master socket where you want the ONT placed or somewhere else. Although there is some leeway where the Fibre cable enters the property there are some limitations, even down to the installers attitude on the day.

The fibre cables used by Openreach are set lengths with one end being pre terminated.

This kit is worth knowing about, https://www.premitel.uk/consultancy/expert-advice/how-to-relocate-the-ont-fibre-termination-point/ there might be others available.

Another consideration is using Power over Ethernet. This injects the 12v dc power source to the ethernet cable, required adapters at both ends. Recommendations for the ethernet cable have all ready been mentioned on this thread.