Friday, December 16, 2011

Can You See it, Now?

The Restoration Crew has moved their gutter installation operation to the North side of the Memorial Church on Historic Jamestowne. As part of the process, the crew uses the scaffold set-up to inspect and replace damaged slate shingles. The lichen growth on the North side of the church was so thick and extensive as to make the slate inspection impossible. Therefore, the decision was made to remove the lichens. Internet research on lichen removal revealed that a solution of two quarts bleach added to a gallon of warm water and TSP might work. As you can see from the left side of the photo, when this solution was applied with a garden sprayer and then scrubbed with brushes, it was mildly effective. Dissatisfied with the results, the crew treated the right side of the roof with the same solution, then used a 1700 psi pressure washer with a 25 degree fan tip. As all Americans obsessed with instant gratification, the crew was pleased with the results. Great care was used to spray in a top-to-bottom motion, so as not to drive water under the slates. An EDPM underlayment, which had been applied to this side of the roof after an earlier roof repair, gave the crew added confidence that the pressure washer wasn't going to cause interior leaks. Since lichens produce an acid that allows their root to grow into stone, it is hoped that its removal may increase the life of the slate shingles. Don't forget to "lich" Preservation Virginia on facebook, for more exciting adventures.

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