What is NBN fibre to the building (FTTB), and is it any good?

What fibre to the building is

Fibre to the building (FTTB) is the type of NBN used in many apartment blocks and some office and retail buildings. NBN runs fibre to the building and stops it at equipment in the basement or the communications room. From there, the building’s existing copper phone wiring carries the service to each unit.

So it is fibre to your building, not fibre to your unit. The last part of the trip, from the basement to your wall socket, is on wiring that was put in when the block was built. When that wiring is the trouble, testing a unit block’s line from the frame to your door is what finds it.

How fibre to the building works

1. 1

   Fibre to the basement

   NBN's fibre arrives at the building and connects to NBN's equipment, usually in a locked cabinet in the basement, a car park or a communications room.

2. 2

   Across the frame

   That equipment is wired to the building's main distribution frame, the MDF. A short wire called a jumper connects NBN's side of the frame to the pair of wires that runs to your unit.

3. 3

   Up the building

   The building's own copper cabling carries the signal up the riser, sometimes through a smaller frame on your floor, to the phone socket in your unit.

4. 4

   The modem on the phone socket

   There is no NBN box in the unit. A VDSL2 modem plugs straight into the phone socket and makes the connection.

The frame and the jumper are worth understanding if you live in a unit, because a surprising number of dead or slow services come down to that one short wire. See what MDF jumpering is, and when the jumper is the fault, we find your pair at the frame, jumper it and tag it.

So is fibre to the building any good?

It can be very good, and it can be poor, and the difference is the building.

The copper run in a unit block is short, basement to unit, which is far less than the run from a street cabinet to a house on fibre to the node. On sound wiring, that short run gives a fast, steady service at the speeds the copper types can carry.

What lets it down is the wiring itself. In an older block, the cabling in the riser may be decades old, the frame may have been worked on by a great many people, and each unit may have several phone sockets still joined to the one line. The service is only as good as the worst part of that path.

Fibre to the building: what works for it and against it

In its favour	Against it
A short copper run, basement to unit	The copper is the building's, and may be as old as the block
No digging or new cabling needed to connect a unit	Cannot take the fastest plans, which need fibre to the premises or HFC
Steady on good wiring	A fault can sit in any of three owners' cabling
The modem plugs into an ordinary phone socket	The frame is shared, so work on another unit's line can disturb yours

Who owns which part of the line

This is the part that causes the most confusion in a unit block, because three different parties own three different stretches of the same line.

• Street to the frame: NBN’s. The fibre and NBN’s equipment at the frame.
• Frame to your front door: the building’s. The riser cabling, any floor frames and the pair to your unit. In most strata schemes this is common property.
• Inside your door: the owner’s. The sockets and the cable in the walls. For a tenant, that means the landlord.

From the basement to one unit

Show the building

Who owns it Where faults hide

1234512345

• Street to the frame: NBN’s
• Frame to your door: the building’s
• Inside your door: the owner’s

1. 1NBN’s equipment in the basement
2. 2The main frame (MDF)
3. 3The riser
4. 4A floor frame
5. 5Your unit
6. 1The jumper at the frame
7. 2The riser cabling
8. 3Old phone sockets inside the unit
9. 4The modem
10. 5The WiFi

When a service is faulty, each party tends to point at the next. The provider says the line tests fine to the building. Strata says it is the provider’s service. The owner or tenant is left in the middle. The way out is a test at the frame, which shows whether the service is arriving at the building properly, and then a test along the building’s cabling to the unit. That finds which stretch the fault is in, and so whose it is.

Managing a building? Our guide for strata and building managers covers the comms room, the frame and the lift phone, with a checklist to print.

What goes wrong on fibre to the building

• The jumper at the frame. Connected to the wrong pair, knocked off during other work, or never run for a new service. From inside the unit it looks like a dead line.
• Old phone sockets inside the unit. Several sockets joined to the one line weaken the signal. An extra socket still on the line is called a bridge tap. See what a bridge tap is.
• The riser cabling. Corroded or damaged pairs between the frame and the unit. This is the building’s cable.
• The modem. An old modem, or one not made for this kind of line.
• The WiFi. In a block of units, dozens of WiFi networks overlap. Slow WiFi in an apartment is very often crowding, not the line, and sorting out WiFi in a unit is its own job.

Which of these it is gets settled by testing, not by guessing. An NBN technician who tests to the boundary can tell you whether the service is arriving at the frame properly, and our NBN fault repair, by what you are seeing, covers the rest.

There is a worked example in a dead line in a new apartment: three faults between the unit and the frame. And a fault that only shows up as lag in games is in a strange noise in the MDF room.

Watch: How I Fixed a Major Internet Issue for a Business In Sydney With No NBN FTTB Cabling

What to check before you ring anyone

• Plug the modem into the first socket in the unit, with no extension lead, splitter or filter.
• Unplug anything else on the phone sockets.
• Test on a cable. If a laptop plugged into the modem is fast and steady, the line and the building are fine and the WiFi is the problem.
• Ask a neighbour. If the whole floor or the whole building is off, it is not your unit.
• If the service is new and has never worked, ask your provider for the pair details at the frame. A new service that will not come up is very often waiting on a jumper.

Check your speed first Run it on a cable at the modem first, then on WiFi. In a unit, the gap between those two numbers is usually the neighbours' WiFi, not your line.

Plans and upgrades on fibre to the building

Any provider’s plan runs over the same NBN equipment in the basement and the same building wiring, so changing provider does not change the line. We do not sell plans or rank providers. Compare them on price, support and the evening speed they publish.

Some buildings can move from fibre to the building to fibre to the premises, with fibre run to each unit. Whether yours can, and what it costs, is NBN’s to answer through its address checker (opens in a new tab), and in a strata building it is a decision for the owners corporation as well as for you. NBN also names a separate program, its Full Fibre Upgrade for Complex Multi-Dwelling Properties, in its statement of 1 July 2026 (opens in a new tab); whether a building is part of it is for NBN to say. Our FTTP upgrade page covers what the cabling work involves.

To see how fibre to the building compares with the other types, see which NBN connection is best.