Freezing temperatures, nesting bees, gushing winds and lashings of rain are to blame for an estimated £10,000 worth of damage to a Dacorum landmark.
Scaffolding was erected at Grade I-listed Ashridge House on Wednesday as the repair work began.
Hospitality director Anna Brown said wind and rain battering the building had knocked off parts of its walls for the first time in the 200-year history of that part of the site.
She said: “The priority for us at the moment is obviously the building – but we have got a wedding on at the weekend.
“If you are booking a wedding here, you do not necessarily want to see scaffolding around the building.”
Mrs Brown said there are fears another section of the wall may have been damaged, and permission is being sought from Dacorum Borough Council to safely remove it.
Microscopic holes were made in the wall of the mansion by freezing temperatures earlier this year which were so small that they were not discovered in its regular surveys.
They were made worse by masonry bees boring into them to make nests, and the final straw came when ferocious winds blew rain into the wall on Saturday.
Ashridge Business School, which owns the building, spends a fortune on its continual upkeep to maintain it as a national landmark.
Spokesman Jenny Murray said: “There is a section of the front facade that has been damaged because it is made of Totternhoe stone – but it is quite a soft stone.”
The limestone material was chosen for the neo-Gothic building, built between 1808 and 1814, because it was easy to carve into beautiful patterns.
Ms Murray said: “Like many buildings in the UK, Ashridge House has been damaged by the recent storm. We are just starting to carry out some of the work now needed to repair it.
“Obviously Ashridge House is a 200-year-old building, so does require constant work to maintain it.”
The holes in the wall will be filled in with ordinary red bricks coloured over with grey render after Dacorum Borough Council grants permission for the work.
There are plans to make good that work with Totternhoe stone next year when it is warm enough to do so.