The completion of the structure will make Franklin's Gardens a 'wraparound arena' and will complete the redevelopment of the home of the Aviva Premiership team, which was started a decade ago.
Saints chairman Leon Barwell said: "We are very pleased to be in the position to confirm not just what the new North Stand will look like, but also when we intend for the development to take place.
"This gives us plenty of time to put together a planning application that takes into account every possible aspect and ensures that we will not be doing a rush job for the sake of it.
"The expansion of Franklin's Gardens is crucial in the long-term development of the club and we want to make sure we do it right."
However, Barwell revealed Northampton may play matches at Milton Keynes' stadium:mk, on occasions when the near-15,500 capacity of Franklin's Gardens is not deemed enough.
He added: "We also have the option of using stadium:mk, which will be increasing in capacity up to 32,000 in the next 12 months and would give many more supporters the opportunity to watch the Saints than we could ever fit into Franklin's Gardens.
"This mirrors what is now common practice across Europe and means we would fit perfectly into the template for professional rugby clubs as laid out recently by business analysts Deloitte - sustainability based on investment in our home ground together with the added profile and income resulting from matches held at a bigger stadium."
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