The building will include two more changing sheds, toilet and shower facilities and storage space.
Throughout the year, Rugby League, Softball and Touch rugby organisations are all key users of the park and its facilities.
With rugby league the main stakeholder, Riccarton Knights manager Tony Greenfell said he was excited that after four or five years of planning, the project was nearly complete.
On top of the council grant, the complex has been funded through community grants and fundraising.
With two fields and four changing sheds, Greenfell said the ability to accommodate four teams at the same time would ease administrative pressure.
Greenfell said registration numbers were grow across all three sports with 360 juniors and seniors regularly using the park. The community was excited to have more space to store gear.
The sheds are expected to open next weekend.