The roof is original to the cathedral, completed in 1915. Although no leaking has been visible inside, cracks in the plaster, mortar and stone show evidence of water damage. The copper roof now provides most ofthe protection against the elements because the tile and felt sub-roof is old and worn. It will be replaced with a nine-layer roof and new copper. The renovation also involves tuckpointing, or replacing deteriorated mortar. Although the building's exterior has top priority, plans call for some patching of the cathedral's ceiling.

As the project progresses, more than 100,000 pounds of scaffolding will be used, 80,000 pounds of planking, 170,000 pounds of temporary structural steel, more than 70 tons of copper, and 167,000 sf of stone will be cleaned, according to church officials.

The roof will lose its green patina, at least until the natural aging process turns it that color in a quarter-century or so. Pre-patina copper is more expensive and more difficult to use because it is less pliable, Nonnemacher says.

Another big challenge is raising the money to pay for the work. The estimated project cost of $35 million is well beyond the ability of the cathedral parish to pay for it. Because the cathedral is considered the mother church for Roman Catholics in the Twin Cities, the Archdiocese of St. Paul and Minneapolis is seeking to raise money from the community at large.