How to Inspect Ridge Vents from the Attic
InspectAPedia® -
Guide to Inspecting Attic and Under-Roof Ventilation - soffit intake
How to Correct Inadequate Attic Venting to Stop Attic Condensation, Ice Dam Leaks, Attic Mold, & Roof Structure Damage
How to detect roof venting deficiencies, attic insulation defects, and attic condensation problems
Questions & answers about attic moisture, condensation & ventilation: check the ridge vent from inside the attic
This article describes common attic ventilation defects easily observed at the ridge or high point of the roof, as visible from the attic or building interior.
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This forms part of "How to Correct Improper or Inadequate Attic or Under-Roof Ventilation in buildings", part of our discussion of "Attic Condensation".
This article describes inspection methods and clues to detect roof venting deficiencies, insulation defects, and attic condensation problems
in buildings. It describes proper roof ventilation placement, amounts, and other details.
You need the gap at the ridge (or "peak") of the roof for the ridge vent to work. Of course some roof shapes such as pyramid or shed roofs merit special techniques to obtain effective intake and exit venting.
But for a simple gable-styled roof structure, here is what a ridge vent looks like from inside the attic of a home.
The ridge vent cut at the roof ridge or peak extends the entire length of the ridge, stopping just a foot or so from either end, and should give 1.5” to 2.5” of open space (no plywood) on either side of the ridge board for attic air to escape out through the ridge vent.
Fake ridge vents: As depicted by the pair of photographs above, sometimes we find that a builder has installed a ridge vent from outside but s/he failed to cut away the roof plywood to provide the exit air path to properly vent the attic. In this case this lazy man's faux ridge vent installed outside should be removed along with any ridge cap shingles below it.
The ridge vent slot should be cut to remove roof sheathing as we described just above (or best, following instructions of the ridge vent manufacturer).
Do not cut into the rafters themselves. Then install the ridge vent again and you'll have a working roof exit vent system.
Roofing Felt Obstructed ridge vents: It’s less common for us to find that a builder cut away plywood for the ridge vent, but that s/he installed building paper or more likely roofing felt over the opening before installing the ridge vent.
In this case just cut away the building paper to expose the underside of the plastic ridge vent mesh, plastic Cor-A-Vent material (looks like a plastic version of the edge of a cardboard box) or the opening into the aluminum ridge vent (depending on which type of ridge vent was installed).
Check that the ridge vent material itself is not blocked by building paper (which you can simply cut away).
Shingle-obstructed ridge vent warning: If when inspecting from the attic and looking up into the slot of removed-plywood at the ridge of the roof you see the under side of a roof shingle, either the roofer made the ridge vent a bit longer than needed, or something else is going on that we’d need to check from outside.
In any case, do not cut away roofing shingles over the ridge vent as you might invite a roof leak.
If your attic or under-roof cavity has a problem with moisture or mold, installing continuous, un-blocked, aggressive exit venting at the ridge is an important step.
Questions & Answers regarding this article
Questions & answers about attic moisture, condensation & ventilation: check the ridge vent from inside the attic
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Alan Carson Carson Dunlop Associates, Toronto, Ontario. Mr. Carson is a home inspection professional, educator, researcher, writer, and a principal of Carson Dunlop Associates, a Toronto home inspection and education firm. Mr. Carson is a past president of ASHI, the American Society of Home Inspectors
Some great illustrations of the proper under-roof ventilation pathways are offered by Carson Dunlop.
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06 & 12/08
John Annunziata, P.E. - NY Metro ASHI during informal chapter discussions about roof and attic ventilation options (1986-1996).
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Thanks to reader F. Terrell for careful technical editing 06/18/2010
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
"The Elimination of Unsafe Guardrails, a Progress Report," Elliott O. Stephenson, Building Standards, March-April 1993
"Are Functional Handrails Within Our Grasp" Jake Pauls, Building Standards, January-February 1991
Access Ramp building codes:
UBC 1003.3.4.3
BOCA 1016.3
ADA 4.8.2
IBC 1010.2
Access Ramp Standards:
ADA (Americans with Disabilities Act), Public Law 101-336. 7/26/90 is very often cited by other sources for good design of stairs and ramps etc. even where disabled individuals are not the design target.
ANSI A117.4 Accessible and Usable buildings and Facilities (earlier version was incorporated into the ADA)
ASTM F 1637, Standard Practice for Safe Walking Surfaces, (Similar to the above standards)
American Plywood Association, APA, "Portland Manufacturing Company, No. 1, a series of monographs on the history of plywood manufacturing",Plywood Pioneers Association, 31 March, 1967, www.apawood.org
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on Asbestos, Its Industrial Applications, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print).
Building Research Council, BRC, nee Small Homes Council, SHC, School of Architecture, University of Illinois at Urbana-Champaign, brc.arch.uiuc.edu. "The Small Homes Council (our original name) was organized in 1944 during the war at the request of the President of the University of Illinois to consider the role of the university in meeting the demand for housing in the United States. Soldiers would be coming home after the war and would be needing good low-cost housing. ... In 1993, the Council became part of the School of Architecture, and since then has been known as the School of Architecture-Building Research Council. ... The Council's researchers answered many critical questions that would affect the quality of the nation's housing stock.
How could homes be designed and built more efficiently?
What kinds of construction and production techniques worked well and which did not?
How did people use different kinds of spaces in their homes?
What roles did community planning, zoning, and interior design play in how neighborhoods worked
"An Example of Colonial Paneling", Norman Morrison Isham, The Metropolitan Museum of Art Bulletin, Vol. 6, No. 5 (May, 1911), pp. 112-116, available by JSTOR.
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Falls and Related Injuries: Slips, Trips, Missteps, and Their Consequences, Lawyers & Judges Publishing, (June 2002), ISBN-10: 0913875430 ISBN-13: 978-0913875438 "Falls in the home and public places are the second leading cause of unintentional injury deaths in the United States, but are overlooked in most literature. This book is unique in that it is entirely devoted to falls. Of use to primary care physicians, nurses, insurance adjusters, architects, writers of building codes, attorneys, or anyone who cares for the elderly, this book will tell you how, why, and when people will likely fall, what most likely will be injured, and how such injuries come about. "
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Pergo AB, division of Perstorp AB, is a Swedish manufacturer or modern laminate flooring products. Information about the U.S. company can be found at http://www.pergo.com where we obtained historical data used in our discussion of the age of flooring materials in buildings.
Plank House Construction: weblog from plankhouse.wordpress.com/2009/01/25/plank-house-construction/ and where plank houses were built by native Americans, see
Large 1:6 Scale Plank House Construction / P8094228,
Photographer: Mike Meuser
06/12/2007 documented at yurokplankhouse.com where scale model Museum quality Yurok Plank Houses are being sold to raise money for the Blue Creek - Ah Pah Traditional Yurok Village project.
Re-Bath, tub lining products is a bath tub relining manufacturer and distributor located in Tempe, Arizona - see rebath.com
Slips, Trips, Missteps and Their Consequences, Second Edition, Gary M. Bakken, H. Harvey Cohen,A. S. Hyde, Jon R. Abele, ISBN-13: 978-1-933264-01-1 or
ISBN 10: 1-933264-01-2,
available from the publisher, Lawyers ^ Judges Publishing Company,Inc., www.lawyersandjudges.com sales@lawyersandjudges.com and also from the InspectAPedia Bookstore (Amazon.com)
The Stairway Manufacturers' Association, (877) 500-5759, provides a pictorial guide to the stair and railing portion of the International Residential Code. [copy on file as http://www.stairways.org/pdf/2006%20Stair%20IRC%20SCREEN.pdf ] -
How to Clean Moldy Wood Framing & Sheathing How to clean/seal mold from/on exposed lumber or plywood subfloor or roof sheathing indoors - some suggestions based on our field and laboratory research
Lighting, proper use of: proper aiming of a good flashlight can disclose hard to see but toxic light or white mold colonies on walls.
Manufactured & Modular Homes: Modular Building Systems Association, MBSA, modularhousing.com, is a trade association promoting and providing links to contact modular builders in North America. Also see the Manufactured Home Owners Association, MHOAA, at www.mhoaa.us. The Manufactured Home Owners Association of America is a National Organization dedicated to the protection of the rights of all people living in Manufactured Housing in the United States.
Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
Mold-Resistant Building Practices, advice from an expert on how to prevent mold after a building flood and how to prevent mold growth in buildings by selection of building materials and by anti-mold construction details.
Slips, Trips, Missteps and Their Consequences, Gary M. Bakken, H. Harvey Cohen, Jon R. Abele, Alvin S. Hyde, Cindy A. LaRue, Lawyers and Judges Publishing; 2 edition (April 2006), ISBN-10: 1933264012 ISBN-13: 978-1933264011
Steps and Stairways, Cleo Baldon & Ib Melchior, Rizzoli, 1989.
"The Dimensions of Stairs", J. M. Fitch et al., Scientific American, October 1974.
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
Weaver: Beaver Board and Upson Board:
Beaver Board and Upson Board: History and Conservation of Early Wallboard, Shelby Weaver,
APT Bulletin, Vol. 28, No. 2/3 (1997), pp. 71-78, Association for Preservation Technology International (APT), available online at JSTOR.
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