Assumption Church

St. Paul, Minnesota

Completed in 1874, this grey limestone church with twin towers and spires is a landmark on the National Register of Historic Places. The limestone used to build the church was quarried in the downtown St. Paul area.

In 1999, a $4 million renovation of the church was performed which included replacement of the original cast-iron tower cornices, structural work on both towers, a new copper roof, gutters and downspouts, and repairs or replacement of stained glass windows.

Roof Spec Inc., in coordination with the Minnesota Historical Society, developed the reroof design and created the working details and drawings. In addition, consulting and construction administrations services were performed during the reroofing process.

The new roof design consisted of lead-coated copper standing seam and shingle material. Unlike uncoated copper, which in time will turn to the familiar green patina, the lead coated copper will develop a soft suede gray patina.

Early in the project, it was discovered that the original steel ties that held heavy cast iron cornice sections in place had deteriorated. It was also found that the masonry wall section below the rafter tails was deteriorated to the point of being rubble. Based on this, the design team developed appropriate corrective measures for the repair of the crumbling masonry, removal of the cast iron gutters and reattachment of the cornices. Although all of the cast iron cornices throughout the church were secured and refurbished, it was decided that the cornices about the east and west towers would need to be replaced. Lead-coated copper was fabricated to match the configuration of the original cornices and attached via a stainless steel gusset assembly to the tower walls.

Ventilation of the attic spaces was not a concern in 1874. However, today’s energy codes required that insulation be introduced into each of the cavity spaces. It was necessary to develop specific details, both at the eave sections and roof-to-wall ventilation at the side aisle roofs and a ridge vent detail for the altar roof. The main nave roof ventilation was provided by louvers in the dormers.