New Roof Scheduled for Spring

By David Cordes

2006

Planning is under way to replace the upper roof on Terrace Hill. Architects at RDG are busy finalizing the drawings and specifications for the project. While much of the roof, such as the slate mansard roof and associated gutters, underwent extensive restoration in 2000, the upper portions of the roof were deferred at that time for several reasons. The existing rubber roof had six to seven years left in life expectancy, and there werent enough funds.

The upper roof was originally covered with terne metal often mistakenly referred to as tin. The metal was applied in long narrow panels that were joined together with ridges in a manner that is referred to as “standing seam.” Upon examination, the slope of the roof is much greater than one might imagine because it is barely visible from the ground. An unusual feature of Terrace Hills roof is a built-in gutter system along the perimeter of the upper roof as well as the gutter system that is built into the cornice at the base of the mansard roof. While this arrangement reduces the weather- related wear to the slate-covered mansard roof, it is a rather complex detail, which translates into a higher replacement cost.

After the state of Iowa acquired Terrace Hill in 1971, issues with the roof became a problem. The roof began to leak after a few years, which slowed progress on other parts of the initial restoration and the adaptive reuse project that was under way. Roof repairs at that time were made with a limited life expectancy. As a result, the roof was again replaced in 1990. This time, the entire upper deck was covered with white EPDM rubber. Again, while this is a system that performs well, it was warranted for only 10 years with a limited life expectancy of around 15 years.

In the spring of 2007, construction is scheduled to begin on the roof again. This time, historically correct standing seam metal will be used, but the metal of choice will be copper instead of terne. Copper will be used because of its superior life expectancy of 50 to 75 years or more. And while the initial cost is higher, the cost over the life of the roof will be less than would be the case with materials that require replacement every 10 to 15 years. An added benefit is that the lower gutter in the cornice and all flashing used in the restoration of the mansard roof were made of copper. The new slates on the mansard roof have an expectancy of 100 years or more and are now hanging on copper nails that will not rust away.

When this project is complete in the summer of 2007, the Terrace Hill mansion will be under a roof completely constructed of copper and slate: materials that are appropriate and routinely used on high-quality residential, government and commercial buildings. This roof will be expected to last well into this century and will likely last until 2080 to 2100 – or perhaps even beyond before tomorrows caretakers of Terrace Hill will have to think about a new roof.

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