Art works and paintings worth more than £12,000 were ruined when water poured into a store room at the Calder Gallery.
Part of the ceiling had also caved in and owners Phil Withersby and Sue Allinson fear the total bill for repairs may run into thousands of pounds more.
Mr Withersby discovered the damage after returning to the business in Market Street following a Christmas and New Year break.
He said the walls were soaking wet, the ceiling had caved in and everything was damp.
"We were due to reopen on January 6 but because of the snow and ice we postponed and I came in to check the e-mails and put a sign up letting people know.
"When I opened the store room door there was water pouring in through the roof."
The recent freeze is thought to have caused a water pipe to burst above the stockroom at the rear of the gallery.
Tenants in a flat above the property, which was not affected by the burst, noticed a drop in water pressure a day before flooding was discovered and Mr Withersby thought water could have been flowing in for up to 36 hours.
Ms Allinson said: "Over £12,000 of original work has been damaged – £5,000 of which was Phil's own work."
Mr Withersby said: "I had just finished two beach scenes and there was one that no-one had even seen yet.
"The ironic thing is that the hole in the pipe is no more than two centimetres long but with mains pressure for so long plenty of water came through."
The drying out process is going on and once completed structural repair works should take two weeks before the process of restocking the gallery begins.
Ms Allinson said: "The artists have been very understanding and supportive.
"We contacted everyone on our mailing lists and we have lots of lovely e-mails back which have really helped to boost morale.
"We're going to open up with an entirely new exhibition, hopefully, by the end of March which will coincide with our fifth anniversary at the end of April."