Sharing the main house's NBN with a granny flat

The job

A family had built a granny flat behind the main house for a relative, and wanted the flat to use the house’s internet instead of paying for a second service.

Two things were already in place. During the build, the electricians had laid a conduit in the ground between the house and the flat. And inside the flat, a Cat6 data cable ran from a point on the outside wall to a socket in the living area.

What was missing was the link between them: a data cable run from the house. There was no cable in the conduit, and nothing at the house end.

Watch: Granny Flat Sharing NBN Internet FTTC With The Main House Connection

How it was done

HouseExisting conduitGranny flat 12345

1. 1A new socket in the house
2. 2Cable through the conduit
3. 3A small box on the flat's wall
4. 4Testing
5. 5The router

1. 1

   A new socket in the house

   We fitted a data socket inside the house beside the router, so the router could be plugged into the new run with an ordinary patch lead.

2. 2

   Cable through the conduit

   We pulled a Cat6 cable from that socket, through the existing conduit, to the flat. The cable was the underground type: gel-filled, so water that gets into the conduit cannot travel into the cable.

3. 3

   A small box on the flat's wall

   Where the conduit came up at the flat, we fitted a weatherproof box. Inside it, the new cable from the house and the flat's own cable were each terminated on a data jack and joined with a short patch lead.

4. 4

   Testing

   The full path, from the socket in the house to the socket in the flat, was tested end to end before any equipment was connected.

5. 5

   The router

   The house's router was set up so the port feeding the flat was live, and the flat's socket came up on the house's connection.

Why it was done that way

• The conduit made the job. Getting a cable between two buildings is normally the expensive part. With a conduit already in the ground there was no digging.
• The right cable for the ground. Indoor cable in an underground conduit fails when water gets in, and water always gets into conduit eventually. Underground-rated cable is made for it.
• Two jacks and a patch lead, not a hard join. Terminating each cable and linking them with a lead means either half can be tested alone later. If something goes wrong in five years, it takes minutes to tell which side it is on. It is the same thinking as a wired network inside the house: every run ends on a socket, and every socket can be tested.
• A cable, not WiFi across the yard. Across a yard and through a brick wall, WiFi is unreliable, and a range extender rarely makes the trip. With the conduit already there, the cable was the easy choice.
• Test before you configure. A router setting cannot fix a cable fault. The cable was proven first.

When sharing is the right answer

Sharing the house’s service suits:

• A flat used by family, where one bill and one account is what everyone wants.
• A flat that cannot have its own service yet, because NBN has not added it.
• A home office or a studio in the yard.

It does not suit a flat let to a tenant who wants their own provider, their own account and their own privacy. That needs a separate NBN service for the flat, and a separate service starts with a call to your provider, not the council. The whole decision is in our guide, NBN for a granny flat: your own service or share the house’s.

Sharing works the same whatever NBN the house has, fibre to the curb included, because the cable starts at the house’s router, not at the NBN box.

What it takes on your property

Every one of these jobs depends on the path between the buildings. If there is a conduit, we need to know where each end comes up and whether it is clear. If there is not, the question is where a trench or a run along a fence could go. Photos of both ends and the ground in between are usually enough to quote from, and you can get a live estimate for a run like this before you send them.

Once the flat is on the house’s connection, the WiFi inside it is a job of its own, and that is the WiFi technician’s work.

Where a cable between the buildings is not practical, a mesh system can sometimes carry the WiFi across instead, as it did on the job below.

Watch: TP-Link Deco Mesh System Installation | Get Fast Wi-Fi in Every Room