To add your decking, then your felt then shingles....the double weight alone would give me pause. Another reason for the tear off is there is give in the shingles...so going over them will not give you a good solid base ( deck).
Also what's to say there is anything wrong with the decking that's there. You might not even have to put up new decking...saving money is always good.
Depending on how bad the shingles are on there now and how many layers there are you might have to replace the underlay anyway and again to go over already compromised decking.....not good at all.
Definitely tear off, much better in long run. One, too much weight on roof can compromise rafters and cause hem to begin to sag and over time see a sway in the roof. 2, it will make it easier to keep up with rafters when nailing down new sheeting
So, Leah, in other words, what you are saying is: Common sense aint so common?
The point I was trying to make is quite simply this: Avondale, your question is so outlandish it doesn't deserve a valid response.
I could go in depth, talk about weight, talk about ice shield, talk about ventilation, talk about flashing, talk about how to choose a quality shingle, etc... but why? I could talk about the pros, being only 1; cheap. I could talk about the cons, being numerous. But I thought my original reply summed that all up into one nice neat package.
Grumpy: :thumbsup: I'm getting more cynical day-by-day.... But the stupidity of others rarely ceases to amaze me. I find the 'friend of a friend' is the major culprit in perpetrating awful advice, but anything on TLC, Discovery, or other 'home improvement' TV show.
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