[MassHistPres] water and slate roofs

[Judy Markland]

Greetings:
Whately has an 1841 Greek Revival town hall that it is hoping to 
rehabilitate with both town and CPA funds.  The roof on the two story 
building is slate and generally in good repair.  Although it has not had a 
complete inspection, the architects estimate that less than 15% needs 
repair.  There are no obvious signs of flaking or delamination.  The slate 
was installed directly over an earlier wood shingle roof, probably in 1871 
when the existing 1-story building was lifted to become the second story.

The consensus is that the roof should be retained and repaired.  However, 
the renovation will make the building very air tight.  A local builder has 
expressed concern that there is no water barrier below the slate, and that 
any water infiltrating will not be able to evaporate as it most likely does 
now, causing timbers and supports to rot.  He suggests removing the slate, 
adding a water barrier, and replacing the slates in good condition.

This will obviously be expensive.  Has anyone had experience with slate 
roofs in tight, energy efficient buildings and, if so, can you recommend a 
course of action?

Judy Markland
Whately Historical Commission