Min Slope for a slate Roof

We have designed a residential bldg in California, with a roof of slope 2:12 with a slate roof.
Now, we understand that the min slope shall be 4:12 per CBC section 1507.7.2. Hence we have to re-design OR use an alternate roof material.

Surprisingly, the Miami-Dade county permits 2:12 slope for the same. So, i'm wondering why CA is more stringent compared to a place with more hurricanes/rainfall!!
Original Post
2:12 for slate? What does the manufacturer require? Ignoring code for a moment, to go back to basics, Architectural Graphic Standards limits slate roofs to 4:12 minimum slope, the same as most but not all shingles.

With that said, are you placing elastomeric underlayment under the whole thing? For purposes of code, you can use one of the ice-and-water-shield products as the "roof" [some like the one MFM produces have a product with an aluminum top face to resist UV and is allowed for use as a finished roof], and treat the tile as a decorative finish.

Mike E
do NOT put a waterproof membrane beneath slate roofing... this can lead to condensation in attic and deterioration of framing and other components... the proper underlayment is standard building paper, and on a slate roof (which is considered 'steep slope') that only serves to protect the building from moisture until the slate is installed, after which it really serves no purpose... get yourself a copy of The Slate Bible...

hil
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