I want to put a metal roof over a single layer of asphalt shingles on a house that is over 100 years old. One roofer says furring strips are imperative as the wood in a house that old must not be sound. The other roofer walked all over the roof and only found two places with bad wood and will replace the wood in those areas. He does not recommend furring in this case because water can condense under the metal and then be trapped when the furring strips act as a dam to hold the water on the roof and then rot out the furring strips. Both roofers are using titanium felting.
kathy wildman
2014-09-09 23:27:32.000000
Furring strips have no application if the wood or structure is compromised. Whatever wood is bad needs to be replaced, even if it is not structural in my opinion.
The second roof is incorrect as well (in my opinion). Putting furring strips (if done correctly) across the roof will allow for some additional above deck ventilation which should keep the condensation at bay.
The ventilation needs to be handled at the attic level and if you haven't had mold, moisture, or rot issues previously as a result of too much moisture, you shouldn't with a properly installed metal roof.
