Tips for Roof Eave Venting on Roofs with no Overhang or Soffit InspectAPedia® -
Adding intake venting at the lower edge of roofs that have no overhang or soffit for the usual intake vent openings
How to Correct Inadequate Attic Venting to Stop Attic Condensation, Ice Dam Leaks, Attic Mold, & Roof Structure Damage
Questions & answers about attic moisture, condensation & ventilation: how to vent a roof with no overhang
This article describes alternatives for venting attics and cathedral ceilings by providing air intake openings at the lower edge or eaves of roofs that have no building overhang or soffit or eaves. Our page top photo shows a cape Cod home in Poughkeepsie New York. This building was constructed with no roof overhang, making roof intake venting tricky to obtain, and risking extra damage from ice dams or gutter overflow leaks.
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Our photo at page top shows a modern synthetic mesh type ridge vent (with modest airflow capacity) and our photo at left shows a typical installation of continuous soffit or eaves intake venting at the lower roof edges of a building.
Problems With Roofs Lacking Any Overhang - No Soffit?
Don't give up on providing roof intake ventilation openings just because your building was constructed with no roof overhangs. In fact, providing exit venting (at a roof ridge or at gable end vents) on a building with no intake venting at the building eaves will increase the building heating costs and can also add to attic or under-roof condensation, moisture, and mold problems.
buildings such as the cape Cod shown at page top may be constructed with no roof overhang whatsoever. While this design offers the advantage of more light entry at the building windows (not shaded by a soffit), owners of buildings built with this design need to watch out for several problems:
Ice dam formation is likely in freezing climates if there is no under-roof ventilation. Ice dam leaks on any building but particularly buildings with no roof overhang increase the chances of water passage on or even inside the building wall, inviting mold, rot, insect damage, and wet insulation.
Gutter overflow leaks, should they occur, will send water running down the building wall, inviting the same problems just listed above, even in climates where freezing and ice dams do not occur.
Increased building heating or cooling cost will occur in heating climates if roof exit venting is provided with no eaves or intake venting. That's because warm air leaks and heat lost into the attic or roof cavity will create a building up-draft of air movement that, unsatisfied by a ready source of makeup or intake air from outside, will draw conditioned air out of the occupied building space instead.
Increased risk of attic or roof cavity condensation, mold, or insect damage will occur for the same reasons just described. In cool or cold weather, moisture laden air drawn into the attic or roof cavity will leave its moisture as condensation on the roof deck underside or in the attic or roof insulation.
Venting Solutions for Roofs with No Overhang or Soffit
Install special roof intake venting products that work at the lower edge of the roof decking, underneath the first course of shingles. Example: Smart Vent™, a special roof eaves vent product that provides a 3/4" opening about 6" above the top of the roof drip edge.
The Smart Vent is a tapered plastic vent product that is combined with a one-inch slot cut into the roof deck six inches from the lower edge of the roof. You will need to be sure that the air vent opening is not blocked by attic or under-roof insulation.
A similar product, the Hicks Starter Vent, patented by Massachusetts inventor Robert M. Hicks, is a combination of roof edge "starter vent" and drip edge. is cited at Roof Venting: Un-Vented Hot Roof Solutions. (We have had trouble finding this product).
Construct a hidden roof intake vent at the top of the building wall by removing the wall top trim or top siding board, cutting away any building sheathing or blocking at the wall top, nailing 1" spacer blocks 16" on center, nailing a new spaced-out wall top trim board along the roof eaves, and screening the opening against insects.
This design is used more often when there is an existing roof overhang but no soffit has been constructed to enclose the overhang.
If you follow this design on a building that has no roof overhang whatsoever, the gutter will need to be removed and re-hung on the new spaced-out fascia board or siding board, and you may need to extend the roof drip edge by 1 3/4" to assure that roof drainage enters the new spaced-out gutter. It should not be necessary, however, to actually extend the roof decking and rafter tails.
Our photo (left) shows a roof fascia vent at the eaves of a home in the Northeastern U.S. though in this case the builder also trimmed out a faux-soffit and fascia board (with no gutter yet installed). Our pen was stuck into the fascia vent opening to demonstrate it's width.
Construct a soffit, or eaves overhang, combined with assuring that an opening is provided all along the top of the building wall by removing any blocking between roof rafters at the top plate, combined with use of roof insulation baffles to assure an air inflow pathway under the roof deck.
Using this approach it may also be necessary to extend the roof deck out to cover the roof edge extension.
This is probably the most-costly solution to an un-vented no-overhang roof design, and is practical only in cases where the building is being modified for other reasons. On buildings where the top of windows are close to the top of the building wall, there may be insufficient space to construct an overhanging roof eave without blocking the windows.
Un-vented roof solutions to buildings with no roof overhang and which are a more distant second-best approach, are discussed at Roof Venting: Un-Vented Hot Roof Solutions.
Questions & Answers regarding this article
Questions & answers about attic moisture, condensation & ventilation: how to vent a roof with no overhang
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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.
The Smart Vent™ by DCI roof intake venting provides an intake at the lower edge of roof decking for difficult cases. See www.dciproducts.com/html/smartvent.htm
The AccuVent™ attic ventilation roof baffle produced by Berger permits insulation to extend over the top plate as far forward as possible. See www.bergerbuildingproducts.com/pdfs/AccuVentAtticVent.pdf
GAF Cobra® and other GAF roof ventilation products: see www.gaf.com/Content/GAF/RES1/ROOF/RS_whyuse_ventchart.asp?viewer=&module=
Thanks to reader Steve P. for suggesting this roof vent discussion for providing roof intake venting when there is no overhang on a roof 7/23/09
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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