Asphalt shingles over slate roof

Hi, ( I apologize in advance if this is in the wrong forum)

What’s the scoop with asphalt over slate? Is this a bad way to go? Seems like the slate could/would be damaged by the nailing…
Is this a roof that has to be replaced? Is it bad news?

Is there any barrier between the asphalt and the slate?

Leaving the slate on there and putting shingles on top is a very, very heavy roof.

It won’t work and you’re 100% right about slate damage from nailing! It’s impossible to drive a nail through a piece of slate w/o breaking it. Even if you could, the new roofing wouldn’t seal right because of the sub-roof contours caused by the thick slate tiles and would fall apart in no time.

I have a lot of experience working with slate roof repairs. It is a great product, nice looking, very expensive, long lasting, but very fragile. Just walking on the roof can often break tiles. When they’re initially installed they come with pre-drilled/formed holes for nailing and you still wind up breaking a few.

If you don’t have to replace them, don’t. Fix the leaks and move on. If the problem is major and the roof sheathing underneath the tiles has to be replaced in areas, do a complete tear-off (If they’re the nice looking higher end ones, maybe you can remove the slate w/o breaking them so you can resell them) and then do the asphalt 3-in-1 shingle system. Most of time slate roofs are repaired not replaced and should never be overlayed.