InspectAPedia ^®

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

This article describes alternatives for providing air intake openings at the lower edge or eaves of roofs that have no building overhang or soffit. 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. This article is part of the series ROOF VENTILATION SPECIFICATIONS and also ATTIC CONDENSATION CAUSE & CURE.

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.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

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 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. Provide continuous soffit or eaves intake venting as we describe at Roof Venting: Soffit Intake Vent-Continuous. 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. See Roof Venting: Proper Locations for another sketch of soffit construction and soffit ventilation details. 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 Roof Solutions.

Share this Article      

...

Technical Reviewers & References

Search InspectAPedia

• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also list books on the specific article topic as well as other references, and information sources.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

INTERIORS of BUILDINGS
AIR BYPASS LEAKS
AIR LEAK DETECTION TOOLS
AIR LEAK MINIMIZATION
AIR SEALING STRATEGIES
BATHROOM VENTILATION
FREEZE-PROOF A BUILDING
ATTIC CONDENSATION CAUSE & CURE
Air Bypass Leaks, Thermal Tracking
Blocked Soffit Intake Vents
CATHEDRAL CEILING INSULATION
Comparing Two Houses
Heat Tapes: Use on Roofs for Ice
HEAT LOSS: How to Calculate Heat Loss in a Building
HOUSEWRAP AIR & VAPOR BARRIERS
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
INSULATION INSPECTION & IMPROVEMENT
Inspect Attics for Moisture or Mold
Inspect Basements for Moisture or Mold
Inspect Building Exterior
Inspect the Ridge Vent System from the Attic
Inspect the Soffit Vent System from the Attic
ROOF VENTILATION SPECIFICATIONS
Roof Venting: Intake - Outlet Area Ratios
Roof Venting: Proper Locations
Roof Venting: Both Ridge & Eaves Venting Needed
Roof Venting: Eaves Intake if no Overhang
Roof Venting: Soffit Intake Vent-Continuous
Roof Venting: Un-Vented Roof Solutions
ROOF VENTING ENERGY SAVING DETAILS
HEAT LOSS: How to Calculate Heat Loss in a Building
HOUSEWRAP AIR & VAPOR BARRIERS
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
INSULATION INSPECTION & IMPROVEMENT
THERMAL TRACKING & HEAT LOSS

• 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 design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• ...

More Information on Building Diagnostic Inspections and Repairs

More Reading about Dealing with Attic Mold, Identifying, Removing, and Preventing Mold in Attics

Be sure to review HOW TO FIND MOLD: How to Inspect Homes and Other Buildings for Mold - the Basics of How to Find Problem Mold Indoors in our Mold Action Guide. Here are other articles that will be helpful in evaluating attic mold presence, causes, and cures:

• What Mold and Allergens Look Like: mold identification photos to help identify mold - choosing what to sample in buildings
• 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.
• Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens.
• How to Find and Test For Mold in Buildings A "how to" photo and text primer on finding and choosing the right spots to test for mold in buildings
• 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.
• Simple Adhesive Tape Sampling of Moldy Surfaces - how to send a mold sample to our lab
• Mold Sampling Methods in the Indoor Environment - In-depth article: detailed critique of popular mold testing methods - Is your mold test kit worth the bother?
• Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
• 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.

InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting

Contact Daniel Friedman for website content suggestions or for fee-paid consulting