only a very vulnerable, completely naive numpty would use spray foam to 'condition' the underside of a tiled roof.
if the tiled covering is so bad that it need replacing, then-replace it. don't go and make it 10 times as difficult by squirting glue all over the underside!
similarly, if the tiles need a membrane underlay, then fit one.
Agree 100% I used to pass a property in Glasgow where this stuff had been sprayed and it had spread on to the outside in so many places it looked as if the building had developed some strange illness.
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