I had the opportunity to inspect an historic 1800s home with a separate guest house in Houston’s Sixth Ward yesterday.
Both the main and guest house had the same 3-tab shingles of the same age, however the guest house roof exhibited tenting at the corners of all tabs. I’m curious as to opinions regarding possible cause. It’s not likely to be from hard butting the shingles during installation as the tenting occurs at all tabs, not just at the seams.
I could not see the underside of the roof decking as the underside was sheetrocked as a cathedral shingle. There is obviously no ventilation for this roof. I’m thinking that the likely cause is expansion and contraction of the roof decking. Many of these older places have planks for roof decking that can expand and contract quite a bit with temp and humidity changes. I expect that this roof gets pretty hot in the Houston summertime with no ventilation. Yesterday was a cool day so the decking would have contracted.
I’d like to hear if this sounds likely to others or if there are alternative theories.