Residents in Gungahlin will have to wait until next year to be hooked up to national broadband network fibres.

Residents in Gungahlin will have to wait until next year to be hooked up to national broadband network fibres. Photo: Nic Walker

RESIDENTS in Gungahlin will have to wait until next year for the first homes to be hooked up to national broadband network fibres.

NBN Co officials told Gungahlin residents the installation would begin between April and June. They attributed the six-month delay to getting an agreement with Telstra to decommission the copper network and provide access to its underground pits and ducts.

NBN Co regional community manager Darren Rudd said Telstra had to upgrade more pits in Ngunnawal and Amaroo because they were the wrong size.

''Telstra have to give up the infrastructure to a certain set of standards - that period of time is usually four months and sometimes it's longer, depending on the number of pits they've got to upgrade,'' he said.

''Some of these pits are 15 years old and they are a smaller size pit than we need … in that remediation phase, in places like Ngunnawal and Amaroo, we've had to replace three times the average of the pits because they are just the wrong size.''

But the problem is also prevalent in the newer suburbs of Franklin and Harrison. ''Some of them we are replacing because they aren't the right size,'' he said.

Mr Rudd said about 4200 premises in the Gungahlin central business district, Harrison and parts of Franklin would be linked to the network as part of the first stage of the installation. ''Once Telstra has done the remediation, that's when we go back and run the fibre,'' he said.

But residents will not be able to use the network until next year.

''Construction finish is end of December … ready for service is January … in the first two modules.''

NBN Co and Telstra said information about how many pits needed remediation work and the cost was commercial-in-confidence.

A spokesman from Telstra said the company agreed to make infrastructure such as pits and pipes fit for purpose.

''Sometimes this involves remediation work such as enlarging pits,'' he said. ''The work carried out [number, location and cost] is commercially sensitive but we can confirm the remediation work under way in Gungahlin is on schedule.''

The estimated cost of building the national broadband network has risen by 3.9 per cent, from $35.9 billion to $37.4 billion.

NBN Co said by June this year it had started or completed construction for about 305,000 premises - below the target set in the first business plan back in 2010.