Roof Slope & Asphalt Shingles

(I posted this about 2-3 weeks ago, just as my campus server crashed. Usenet has been down (here) since then, so I don't know if this appeared or not, or if there were any responses.)
I'm aware of a common rule of thumb saying something like slopes less than 3 or 4 in 12 should not have shingles. I live in a development where all the homes are 25 years old. In the last 5 years several neighbors have replaced their roofs; even on slopes of 1 in 12 they have all used asphalt shingles, the same as the rest of their (steeper) roofs.
I plan to have my roof replaced this summer, and so far have been unable to learn of a code REQUIREMENT, in contrast to "general knowledge" about there being a minimum slope for asphalt shingles.
I'm located in Southern California, in an area that gets very little rain.
Any knowledge, advice, and/or insight appreciated.
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CWLee
Former slayer of dragons; practice now limited to sacred
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CWLee wrote:

warranty; consult with them. Minimum slope is not just a leaking roof issue, its also wind resistance.
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Grandpa Koca - SAHD for 6 - Keeper of the Perpetual Kindergarten
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International Residential Code Section 905 says in essence: Asphalt shingles on solid deck sloped between 2 in 12 & 4 in 12 requires shall have two layers of underlayment.
Ice & water shield is a good idea on slopes this shallow. TB
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you are correct, that is too low of a slope
http://www.iko.com/misc/CasmaPdf/16-LowSlopedRoofs.PDF
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low sloped roofs (under 4/12) may be shingled as long as the shingles are double sealed. as for the ice and water shield, the shingles are just a formality as the ice shield is the water barrier itself. i would treat the roof as a flat and apply the appropriate membrane such as torch applied, etc.

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I applied ashpalt shingles to my 2:12 sloped roof about 12 years ago. As posted above, the only code requirement was a double layer of felt. I live in an area with a moderate climate and had no problems.
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