Dundalk will build a temporary stand in an effort to satisfy huge ticket demand for Friday's SSE Airtricity Premier Division decider against Cork City, with tickets selling out in an hour this morning.
Oriel Park's capacity is limited to just over 3,700 for safety reasons.
But the new structure will allow an extra 750 fans to attend the game.
Cork have been restricted to an away allocation of 700 tickets, although they requested more than double that amount.
The extra tickets sold out in around an hour this morning.
A Dundalk FC statement read: "It is clear to us that we could have sold this match out three times over given the level of demand.
"We regret that there will be some supporters that have been unable to purchase tickets.
"This is despite considerably increasing our capacity with the installation of a very expensive temporary stand. We are very sorry to those who are disappointed.
"Unfortunately, the club has strict limits to our capacity and we are unable to exceed these numbers."
The match is live on RTÉ2 from 7.30pm on Friday.
Big crowds outside Oriel Park queuing for tickets for @DundalkFC's title decider with @CorkCityFC. Picture by @cul7 pic.twitter.com/NvzsenrD3D
— Gavin McLaughlin (@McLaughlinGavin) October 22, 2014