The Barnard Castle saleroom will shut on August 14. Addisons say this follows a move "to focus on the estate and land agency aspect of the business, which has grown substantially in recent years".
They have also been looking "for some time for new premises to accommodate the auction house but no suitable sites have presented themselves - another factor that has contributed to this decision".
"It is with great regret that we have taken the step to close the auction rooms," says Simon Nixon, auctioneer and principal partner, "but it does seem like an appropriate time to restructure the company.
"Over the many years of trading we have built up excellent relationships with clients and will sadly miss all those who have crossed our threshold. We hope the salerooms will be fondly remembered not only as a place to come and see a multitude of amazing and interesting objects but also as a meeting place for friends and families."
The last Antiques and Interiors Sale will be held on Thursday, July 23. Any uncollected items from previous sales will be sold at this auction without reserve.