|Posted on Friday, July 23, 2004 - 08:41 am: ||
We have two slate roofs that have wood shakes (shingles) underneath. Was this a common underlayment technique, or did these buildings (1810 and 1867) have slate roofs added decades after they were first built?
Are there any issues with reparing and maintaining roofs that have shakes underneath?
When replacing a section of roof that has a dozen or so slates missing, should the shakes be removed, left or replace?
Is a slate roof enough heavier than a snow-laden shake roof to be of concern regarding the strength of the roof structure?
Shelburne Falls (MA) Trolley Museum
|Posted on Saturday, July 24, 2004 - 08:12 pm: ||
Some roofs had slate overlaid over the original wooden shingle roof,since slate wasn't common in our area until the 1840's.Homes built prior to this usually had a wood roof,and just as today some people opt to overlay a second roof over the first.Now it would be more common to see two layers of asphalt shingle on newer constuction,but the same desire to save money by not removing the first roof applies.
As the wood dries out over decades and starts to crumble under the slate,it makes repair more difficult and more slate nails with less hold on the deck below.
If you repair a section and remove the shakes you'll need to add boards or shims to space up the surface to renail the new slate.Standard length hooks don't work as well becase of the extra thickness.
The best solution is to remove both layers,salvaging as much slate as possible,dispose of the shakes,then relay the slate with appropriate make up slates.obviously not a cheap solution but a long term investment if the bulk of the slate is sound.