Thread: Ridge Vent.

Inspected a house today that had a ridge vent properly installed but the plywood cut underneath the ridge vent varied from 1/4" inch in someplaces to 2" inches on each side of the ridge board. What is the standard or the code for such an opening?

Thanks, Jim

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There should be about 1-1/2" gap between the decking at the ridge. There also needs to be additional venting (preferrably a continuous soffit vent on each side) for a ridge vent to work.

I call out most attics for needing to improve venting. The only way to effectively ventilate an attic using a passive venting system is a properly installed continuous ridge vent in combination with continuous, unblocked, soffit vents.

Thanks Jon,

There was a soffit vent but as stated earlier, the gap was all over the place. Less than an 1/2" in places and wider in others. I recommended a roof fan controled by a temperature gauge or humidistat.

I just recommend improvement and let them know what I consider to be the best combination. How/if they improvement is up to them. There is some evidence that powered fans are not that effective either. The fan will be installed at a gable vent according to the instructions, but in reality it will pull air in trough the nearest opening (ridge vent) and blow it out of the gable - bypassing the rest of the attic.

Cor a Vent says 1 1/2 on each side of ridge. Think this is typical.
http://www.cor-a-vent.com/pdf/4pg-install.pdf

I recommended a roof fan controlled by a temperature gauge or humidistat.

Jim, this is from another Jim , I have found power ventilators to be about the worst possible ventilation product out there in my research and personal experience. You may live in a totally different climate that would change my thinking, but around here there are just too many draw backs.
Short life, high energy cost, and drawing conditioned air out of the house are just a few. I don't think I have ever seen one still alive after more than 5 years, typically they are toast after 3 years.
Just me, but I would not recommend installing a power ventilator in an attic unless it was the last possible alternative... and maybe not even then.
JMHO - the other Jim

Originally Posted by David Banks

Cor a Vent says 1 1/2 on each side of ridge. Think this is typical.
http://www.cor-a-vent.com/pdf/4pg-install.pdf

We always try to get 2" from the center of the ridge. Otherwise with a 2x ridge board you only get an effective 3/4" air gap on each side. Never been a problem with fastening or leaking. An extra 1/2" along the entire ridge, on each side, surprisingly makes a big difference with ventilation.