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Is ventilation required with a low-slope roof in mild climate?

Sam9876 | Posted in General Questions on

Hello All. 

Is ventilation required for a low-slope roof in a mild climate?

We are doing advance planning for a 2nd story addition to our home.  We live on the coast of California.  Extremely mild climate year round — never gets too hot or cold. Our home is very close to the ocean so we have more humidity than inland California,  but relative to the the East Coast very little humidity.  Little rain and wind relative to the rest of the country.

We have a strict height requirement we have to comply with.  We can squeeze in just under the height requirement if we use a low-slope roof with  a  ratio of 5/8″ height gain for every 1 foot.  We were thinking of using a good quality metal roof  that is rated for slopes as low as 1/2″ : foot,  since they shed water and prevent leaks better than other flat/low-slope roof options,  and last longer.    (We would use a panel type metal roof,  standing-seam profile, aluminum, with color pre-applied at the factory.)  We are halfway up  a gentle hill rising from the ocean so the uphill homes will be able to see our roof — another reason we want to go with a standing seam metal roof.

We literally have only an inch spare to come in under the mandatory height limit. 

Does a low-slope roof even require ventilation like a normal pitched roof???    If yes,  is there a way to ventilate it that adds no more than an inch of height???   

Thanks in advance to everyone.

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  1. Expert Member


    You don't need to add ventilation, and it wouldn't help anyway. It's almost impossible to effectively ventilate a low-slope roof, so you need to use an assembly designed to work without ventilation. That typically uses completely different materials:

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