The contractor completed the £25m stand for the Jockey Club in 2009.
Part of the roof “the size of a tennis court” was blown off in strong winds on Christmas Eve.
The incident came two years after parts of the same roof where ripped off during a bout of severe weather.
A Willmott Dixon spokesman told the Epsom Guardian the company is working with the roof’s architects to find a solution which will ensure the incident does not happen a third time.
He said: “There has been a little bit damage to the roof. It’s not a significant amount.
“The sheer force and intensity of the wind has caused a section of it to become unstuck.
“We are concerned on the basis that we need to address this so it doesn’t happen again.
“We are speaking to the architects and will come up with a solution.
“It has been built to all the specification standards but for some reason again it has come away.”
He said the company are not considering altering the design of the roof or installing a new one and that any repair work will involve “strengthening and reinforcing” the existing roof.
He added: “We are putting out best people on this to make sure it doesn’t happen again. We won’t leave it until we are satisfied it will not happen again.”