[PaulDavisThe1st]

"Tile" in the US probably (though not definitively) means "spanish tile" - those terracotta curved tiles. It's not the same as what I remember tile meaning in the UK, which was typically slate.

Also, I spoke with some roofers in Pennsylvania who explained to me the difference between Welsh slate and the stuff from PA ... way less durable because the layers are not as tightly bonded, and then you add freeze/thaw and it just doesn't last as long.

[rsj_hn]

correct, Also the underlay needs to be replaced often and if it's not the tiles can come loose or get damaged. Replacing the underlay requires removing all the tile, which is labor intensive, and then depending on the HOA/owner preferences, you can try to color match damaged tiles or replace the tiles, or replace portions, all of these are done regularly. Depending on type of underlay used, it might need to be replaced every 7-25 years, again depending on the weather conditions and materials used.