Zinc roofing on Hunstanton’s newly-refurbished butterfly shelters is set to be replaced because of discolouration.
West Norfolk Council officials say the work will begin on Monday after manufacturers acknowledged the material was not of the required standard.
The authority says it will not face any extra costs.
Deputy leader Elizabeth Nockolds said: “This is a Heritage Lottery Funded project and it is vital that it is up to standard and will last for years to come.
“I’m pleased we picked up the problem while still under warranty so that the matter can be dealt with as quickly as possible with no cost to taxpayers.
“It is unfortunate we will have to close the shelters while the work is done, but they will be re-opened as soon as possible.”