Roofing/roof ridge vent

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Question
Hi Bruce!
Is it necessary for a roof to have a ridge vent when there isn't even an attic? Why or why not?
The second floor of this home (built in 1920) has two small beds and a bath. Each bedroom has a crawl space for storage and is accessed with a door in each bedroom. There is no attic above the second floor. I've enclosed an image.
Hope to hear from you soon....
Best regards,
Angelina

Answer
Angelina,

I did not receive the image, but based upon your description I am envisioning a pitched ceiling that has been attached to the underside of the roof rafters.  Insulation blankets most likely exist between the rafters on top of the ceiling and under the roof sheathing immediately above.

The point of the ridge venting is to provide passive ventilation from the soffit to the ridge to remove moisture leaving the interior of the residence preventing condensation and deterioration.  With this type of configuration (assumed)a continuous ridge vent would be required as each rafter bay is individualized and enclosed on the top by roof sheathing and on the bottom by the ceiling. The ridge vent will only work properly if there is an air space between the bottom of the roof sheathing and the top of the insulating blankets within the rafter bay.  So some investigation may be warranted to verify this.

If there is no insulation and the performance and the interior environment is satisfactory and there appears to be no structural problems related to condensation, or no changes are being made to the ceiling/roof assembly, I would refrain from making alterations for the sake of it; preventing the occurrence of unintended consequences.  If you have a good reason for changing the current roof/ceiling assembly, a thorough understanding of what you have is important to knowing that your efforts will result in effective and positive changes.

Please feel free to follow up with me if you need to.

Regards,

Bruce Ryan II, RRO
Professional Roof Consultants, Inc.

Roofing

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Bruce A. Ryan II, RRO

Expertise

I offer solid knowlege of all types of Commercial and Residential Roofing, Waterproofing, and, Building Envelope systems. Experience ranges across low slope and steep slope roof systems. I am also well versed in matters regarding condensation and ventilation. I enjoy donating some of my time and knowledge to the betterment of others.

Experience

Bruce Ryan has 20 years of roofing, waterproofing, and building envelope consulting experience with PRC, with 5 years of commercial roofing experience prior to joining the firm. He became Vice President of the company in 1998. Bruce Ryan plays a key role in the development of practical, long-term roofing and waterproofing solutions, along with implementation of on-site forensic studies. Bruce also has a high level of experience with regard to the impacts of roofing materials and construction for demanding clients with heavily occupied structures.

Organizations
Oregon Construction Contractors Board Construction Specifiers Institute National Roofing Contractors Association The Institute of Roofing, Waterproofing, & Building Envelope Professionals Oregon Board of Investigators Installation Masters

Education/Credentials
University of Maryland BS Business & Administration Registered Roof Observer - RCI Private Investigator Certified EIFS inspector - Northwest Wall and Ceiling Bureau Certified InstallationMaster™ - The Installation Masters™ Training and Certification Program (developed by American Architectural Manufacturers Association)

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